linux/kernel/signal.c

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/*
* linux/kernel/signal.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* 1997-11-02 Modified for POSIX.1b signals by Richard Henderson
*
* 2003-06-02 Jim Houston - Concurrent Computer Corp.
* Changes to use preallocated sigqueue structures
* to allow signals to be sent reliably.
*/
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/sched/mm.h>
#include <linux/sched/user.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/cputime.h>
#include <linux/fs.h>
#include <linux/tty.h>
#include <linux/binfmts.h>
#include <linux/coredump.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/ptrace.h>
#include <linux/signal.h>
signal/timer/event: signalfd core This patch series implements the new signalfd() system call. I took part of the original Linus code (and you know how badly it can be broken :), and I added even more breakage ;) Signals are fetched from the same signal queue used by the process, so signalfd will compete with standard kernel delivery in dequeue_signal(). If you want to reliably fetch signals on the signalfd file, you need to block them with sigprocmask(SIG_BLOCK). This seems to be working fine on my Dual Opteron machine. I made a quick test program for it: http://www.xmailserver.org/signafd-test.c The signalfd() system call implements signal delivery into a file descriptor receiver. The signalfd file descriptor if created with the following API: int signalfd(int ufd, const sigset_t *mask, size_t masksize); The "ufd" parameter allows to change an existing signalfd sigmask, w/out going to close/create cycle (Linus idea). Use "ufd" == -1 if you want a brand new signalfd file. The "mask" allows to specify the signal mask of signals that we are interested in. The "masksize" parameter is the size of "mask". The signalfd fd supports the poll(2) and read(2) system calls. The poll(2) will return POLLIN when signals are available to be dequeued. As a direct consequence of supporting the Linux poll subsystem, the signalfd fd can use used together with epoll(2) too. The read(2) system call will return a "struct signalfd_siginfo" structure in the userspace supplied buffer. The return value is the number of bytes copied in the supplied buffer, or -1 in case of error. The read(2) call can also return 0, in case the sighand structure to which the signalfd was attached, has been orphaned. The O_NONBLOCK flag is also supported, and read(2) will return -EAGAIN in case no signal is available. If the size of the buffer passed to read(2) is lower than sizeof(struct signalfd_siginfo), -EINVAL is returned. A read from the signalfd can also return -ERESTARTSYS in case a signal hits the process. The format of the struct signalfd_siginfo is, and the valid fields depends of the (->code & __SI_MASK) value, in the same way a struct siginfo would: struct signalfd_siginfo { __u32 signo; /* si_signo */ __s32 err; /* si_errno */ __s32 code; /* si_code */ __u32 pid; /* si_pid */ __u32 uid; /* si_uid */ __s32 fd; /* si_fd */ __u32 tid; /* si_fd */ __u32 band; /* si_band */ __u32 overrun; /* si_overrun */ __u32 trapno; /* si_trapno */ __s32 status; /* si_status */ __s32 svint; /* si_int */ __u64 svptr; /* si_ptr */ __u64 utime; /* si_utime */ __u64 stime; /* si_stime */ __u64 addr; /* si_addr */ }; [akpm@linux-foundation.org: fix signalfd_copyinfo() on i386] Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-11 05:23:13 +00:00
#include <linux/signalfd.h>
#include <linux/ratelimit.h>
#include <linux/tracehook.h>
#include <linux/capability.h>
#include <linux/freezer.h>
#include <linux/pid_namespace.h>
#include <linux/nsproxy.h>
user namespace: make signal.c respect user namespaces ipc/mqueue.c: for __SI_MESQ, convert the uid being sent to recipient's user namespace. (new, thanks Oleg) __send_signal: convert current's uid to the recipient's user namespace for any siginfo which is not SI_FROMKERNEL (patch from Oleg, thanks again :) do_notify_parent and do_notify_parent_cldstop: map task's uid to parent's user namespace ptrace_signal maps parent's uid into current's user namespace before including in signal to current. IIUC Oleg has argued that this shouldn't matter as the debugger will play with it, but it seems like not converting the value currently being set is misleading. Changelog: Sep 20: Inspired by Oleg's suggestion, define map_cred_ns() helper to simplify callers and help make clear what we are translating (which uid into which namespace). Passing the target task would make callers even easier to read, but we pass in user_ns because current_user_ns() != task_cred_xxx(current, user_ns). Sep 20: As recommended by Oleg, also put task_pid_vnr() under rcu_read_lock in ptrace_signal(). Sep 23: In send_signal(), detect when (user) signal is coming from an ancestor or unrelated user namespace. Pass that on to __send_signal, which sets si_uid to 0 or overflowuid if needed. Oct 12: Base on Oleg's fixup_uid() patch. On top of that, handle all SI_FROMKERNEL cases at callers, because we can't assume sender is current in those cases. Nov 10: (mhelsley) rename fixup_uid to more meaningful usern_fixup_signal_uid Nov 10: (akpm) make the !CONFIG_USER_NS case clearer Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Serge Hallyn <serge.hallyn@canonical.com> Subject: __send_signal: pass q->info, not info, to userns_fixup_signal_uid (v2) Eric Biederman pointed out that passing info is a bug and could lead to a NULL pointer deref to boot. A collection of signal, securebits, filecaps, cap_bounds, and a few other ltp tests passed with this kernel. Changelog: Nov 18: previous patch missed a leading '&' Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Dan Carpenter <dan.carpenter@oracle.com> Subject: ipc/mqueue: lock() => unlock() typo There was a double lock typo introduced in b085f4bd6b21 "user namespace: make signal.c respect user namespaces" Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Serge Hallyn <serge@hallyn.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-10 23:11:37 +00:00
#include <linux/user_namespace.h>
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
#include <linux/uprobes.h>
#include <linux/compat.h>
#include <linux/cn_proc.h>
#include <linux/compiler.h>
#include <linux/posix-timers.h>
livepatch: send a fake signal to all blocking tasks Live patching consistency model is of LEAVE_PATCHED_SET and SWITCH_THREAD. This means that all tasks in the system have to be marked one by one as safe to call a new patched function. Safe means when a task is not (sleeping) in a set of patched functions. That is, no patched function is on the task's stack. Another clearly safe place is the boundary between kernel and userspace. The patching waits for all tasks to get outside of the patched set or to cross the boundary. The transition is completed afterwards. The problem is that a task can block the transition for quite a long time, if not forever. It could sleep in a set of patched functions, for example. Luckily we can force the task to leave the set by sending it a fake signal, that is a signal with no data in signal pending structures (no handler, no sign of proper signal delivered). Suspend/freezer use this to freeze the tasks as well. The task gets TIF_SIGPENDING set and is woken up (if it has been sleeping in the kernel before) or kicked by rescheduling IPI (if it was running on other CPU). This causes the task to go to kernel/userspace boundary where the signal would be handled and the task would be marked as safe in terms of live patching. There are tasks which are not affected by this technique though. The fake signal is not sent to kthreads. They should be handled differently. They can be woken up so they leave the patched set and their TIF_PATCH_PENDING can be cleared thanks to stack checking. For the sake of completeness, if the task is in TASK_RUNNING state but not currently running on some CPU it doesn't get the IPI, but it would eventually handle the signal anyway. Second, if the task runs in the kernel (in TASK_RUNNING state) it gets the IPI, but the signal is not handled on return from the interrupt. It would be handled on return to the userspace in the future when the fake signal is sent again. Stack checking deals with these cases in a better way. If the task was sleeping in a syscall it would be woken by our fake signal, it would check if TIF_SIGPENDING is set (by calling signal_pending() predicate) and return ERESTART* or EINTR. Syscalls with ERESTART* return values are restarted in case of the fake signal (see do_signal()). EINTR is propagated back to the userspace program. This could disturb the program, but... * each process dealing with signals should react accordingly to EINTR return values. * syscalls returning EINTR happen to be quite common situation in the system even if no fake signal is sent. * freezer sends the fake signal and does not deal with EINTR anyhow. Thus EINTR values are returned when the system is resumed. The very safe marking is done in architectures' "entry" on syscall and interrupt/exception exit paths, and in a stack checking functions of livepatch. TIF_PATCH_PENDING is cleared and the next recalc_sigpending() drops TIF_SIGPENDING. In connection with this, also call klp_update_patch_state() before do_signal(), so that recalc_sigpending() in dequeue_signal() can clear TIF_PATCH_PENDING immediately and thus prevent a double call of do_signal(). Note that the fake signal is not sent to stopped/traced tasks. Such task prevents the patching to finish till it continues again (is not traced anymore). Last, sending the fake signal is not automatic. It is done only when admin requests it by writing 1 to signal sysfs attribute in livepatch sysfs directory. Signed-off-by: Miroslav Benes <mbenes@suse.cz> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: linuxppc-dev@lists.ozlabs.org Cc: x86@kernel.org Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2017-11-15 13:50:13 +00:00
#include <linux/livepatch.h>
#define CREATE_TRACE_POINTS
#include <trace/events/signal.h>
#include <asm/param.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
#include <asm/siginfo.h>
#include <asm/cacheflush.h>
#include "audit.h" /* audit_signal_info() */
/*
* SLAB caches for signal bits.
*/
static struct kmem_cache *sigqueue_cachep;
int print_fatal_signals __read_mostly;
static void __user *sig_handler(struct task_struct *t, int sig)
{
return t->sighand->action[sig - 1].sa.sa_handler;
}
static int sig_handler_ignored(void __user *handler, int sig)
{
/* Is it explicitly or implicitly ignored? */
return handler == SIG_IGN ||
(handler == SIG_DFL && sig_kernel_ignore(sig));
}
static int sig_task_ignored(struct task_struct *t, int sig, bool force)
{
void __user *handler;
handler = sig_handler(t, sig);
if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
handler == SIG_DFL && !(force && sig_kernel_only(sig)))
return 1;
return sig_handler_ignored(handler, sig);
}
static int sig_ignored(struct task_struct *t, int sig, bool force)
{
/*
* Blocked signals are never ignored, since the
* signal handler may change by the time it is
* unblocked.
*/
if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
return 0;
/*
* Tracers may want to know about even ignored signal unless it
* is SIGKILL which can't be reported anyway but can be ignored
* by SIGNAL_UNKILLABLE task.
*/
if (t->ptrace && sig != SIGKILL)
return 0;
return sig_task_ignored(t, sig, force);
}
/*
* Re-calculate pending state from the set of locally pending
* signals, globally pending signals, and blocked signals.
*/
static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
{
unsigned long ready;
long i;
switch (_NSIG_WORDS) {
default:
for (i = _NSIG_WORDS, ready = 0; --i >= 0 ;)
ready |= signal->sig[i] &~ blocked->sig[i];
break;
case 4: ready = signal->sig[3] &~ blocked->sig[3];
ready |= signal->sig[2] &~ blocked->sig[2];
ready |= signal->sig[1] &~ blocked->sig[1];
ready |= signal->sig[0] &~ blocked->sig[0];
break;
case 2: ready = signal->sig[1] &~ blocked->sig[1];
ready |= signal->sig[0] &~ blocked->sig[0];
break;
case 1: ready = signal->sig[0] &~ blocked->sig[0];
}
return ready != 0;
}
#define PENDING(p,b) has_pending_signals(&(p)->signal, (b))
static int recalc_sigpending_tsk(struct task_struct *t)
{
if ((t->jobctl & JOBCTL_PENDING_MASK) ||
PENDING(&t->pending, &t->blocked) ||
PENDING(&t->signal->shared_pending, &t->blocked)) {
set_tsk_thread_flag(t, TIF_SIGPENDING);
return 1;
}
/*
* We must never clear the flag in another thread, or in current
* when it's possible the current syscall is returning -ERESTART*.
* So we don't clear it here, and only callers who know they should do.
*/
return 0;
}
/*
* After recalculating TIF_SIGPENDING, we need to make sure the task wakes up.
* This is superfluous when called on current, the wakeup is a harmless no-op.
*/
void recalc_sigpending_and_wake(struct task_struct *t)
{
if (recalc_sigpending_tsk(t))
signal_wake_up(t, 0);
}
void recalc_sigpending(void)
{
livepatch: send a fake signal to all blocking tasks Live patching consistency model is of LEAVE_PATCHED_SET and SWITCH_THREAD. This means that all tasks in the system have to be marked one by one as safe to call a new patched function. Safe means when a task is not (sleeping) in a set of patched functions. That is, no patched function is on the task's stack. Another clearly safe place is the boundary between kernel and userspace. The patching waits for all tasks to get outside of the patched set or to cross the boundary. The transition is completed afterwards. The problem is that a task can block the transition for quite a long time, if not forever. It could sleep in a set of patched functions, for example. Luckily we can force the task to leave the set by sending it a fake signal, that is a signal with no data in signal pending structures (no handler, no sign of proper signal delivered). Suspend/freezer use this to freeze the tasks as well. The task gets TIF_SIGPENDING set and is woken up (if it has been sleeping in the kernel before) or kicked by rescheduling IPI (if it was running on other CPU). This causes the task to go to kernel/userspace boundary where the signal would be handled and the task would be marked as safe in terms of live patching. There are tasks which are not affected by this technique though. The fake signal is not sent to kthreads. They should be handled differently. They can be woken up so they leave the patched set and their TIF_PATCH_PENDING can be cleared thanks to stack checking. For the sake of completeness, if the task is in TASK_RUNNING state but not currently running on some CPU it doesn't get the IPI, but it would eventually handle the signal anyway. Second, if the task runs in the kernel (in TASK_RUNNING state) it gets the IPI, but the signal is not handled on return from the interrupt. It would be handled on return to the userspace in the future when the fake signal is sent again. Stack checking deals with these cases in a better way. If the task was sleeping in a syscall it would be woken by our fake signal, it would check if TIF_SIGPENDING is set (by calling signal_pending() predicate) and return ERESTART* or EINTR. Syscalls with ERESTART* return values are restarted in case of the fake signal (see do_signal()). EINTR is propagated back to the userspace program. This could disturb the program, but... * each process dealing with signals should react accordingly to EINTR return values. * syscalls returning EINTR happen to be quite common situation in the system even if no fake signal is sent. * freezer sends the fake signal and does not deal with EINTR anyhow. Thus EINTR values are returned when the system is resumed. The very safe marking is done in architectures' "entry" on syscall and interrupt/exception exit paths, and in a stack checking functions of livepatch. TIF_PATCH_PENDING is cleared and the next recalc_sigpending() drops TIF_SIGPENDING. In connection with this, also call klp_update_patch_state() before do_signal(), so that recalc_sigpending() in dequeue_signal() can clear TIF_PATCH_PENDING immediately and thus prevent a double call of do_signal(). Note that the fake signal is not sent to stopped/traced tasks. Such task prevents the patching to finish till it continues again (is not traced anymore). Last, sending the fake signal is not automatic. It is done only when admin requests it by writing 1 to signal sysfs attribute in livepatch sysfs directory. Signed-off-by: Miroslav Benes <mbenes@suse.cz> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: linuxppc-dev@lists.ozlabs.org Cc: x86@kernel.org Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2017-11-15 13:50:13 +00:00
if (!recalc_sigpending_tsk(current) && !freezing(current) &&
!klp_patch_pending(current))
clear_thread_flag(TIF_SIGPENDING);
}
/* Given the mask, find the first available signal that should be serviced. */
#define SYNCHRONOUS_MASK \
(sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
signal, x86: add SIGSYS info and make it synchronous. This change enables SIGSYS, defines _sigfields._sigsys, and adds x86 (compat) arch support. _sigsys defines fields which allow a signal handler to receive the triggering system call number, the relevant AUDIT_ARCH_* value for that number, and the address of the callsite. SIGSYS is added to the SYNCHRONOUS_MASK because it is desirable for it to have setup_frame() called for it. The goal is to ensure that ucontext_t reflects the machine state from the time-of-syscall and not from another signal handler. The first consumer of SIGSYS would be seccomp filter. In particular, a filter program could specify a new return value, SECCOMP_RET_TRAP, which would result in the system call being denied and the calling thread signaled. This also means that implementing arch-specific support can be dependent upon HAVE_ARCH_SECCOMP_FILTER. Suggested-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Will Drewry <wad@chromium.org> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Reviewed-by: H. Peter Anvin <hpa@zytor.com> Acked-by: Eric Paris <eparis@redhat.com> v18: - added acked by, rebase v17: - rebase and reviewed-by addition v14: - rebase/nochanges v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc v12: - reworded changelog (oleg@redhat.com) v11: - fix dropped words in the change description - added fallback copy_siginfo support. - added __ARCH_SIGSYS define to allow stepped arch support. v10: - first version based on suggestion Signed-off-by: James Morris <james.l.morris@oracle.com>
2012-04-12 21:48:00 +00:00
sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS))
signal/timer/event: signalfd core This patch series implements the new signalfd() system call. I took part of the original Linus code (and you know how badly it can be broken :), and I added even more breakage ;) Signals are fetched from the same signal queue used by the process, so signalfd will compete with standard kernel delivery in dequeue_signal(). If you want to reliably fetch signals on the signalfd file, you need to block them with sigprocmask(SIG_BLOCK). This seems to be working fine on my Dual Opteron machine. I made a quick test program for it: http://www.xmailserver.org/signafd-test.c The signalfd() system call implements signal delivery into a file descriptor receiver. The signalfd file descriptor if created with the following API: int signalfd(int ufd, const sigset_t *mask, size_t masksize); The "ufd" parameter allows to change an existing signalfd sigmask, w/out going to close/create cycle (Linus idea). Use "ufd" == -1 if you want a brand new signalfd file. The "mask" allows to specify the signal mask of signals that we are interested in. The "masksize" parameter is the size of "mask". The signalfd fd supports the poll(2) and read(2) system calls. The poll(2) will return POLLIN when signals are available to be dequeued. As a direct consequence of supporting the Linux poll subsystem, the signalfd fd can use used together with epoll(2) too. The read(2) system call will return a "struct signalfd_siginfo" structure in the userspace supplied buffer. The return value is the number of bytes copied in the supplied buffer, or -1 in case of error. The read(2) call can also return 0, in case the sighand structure to which the signalfd was attached, has been orphaned. The O_NONBLOCK flag is also supported, and read(2) will return -EAGAIN in case no signal is available. If the size of the buffer passed to read(2) is lower than sizeof(struct signalfd_siginfo), -EINVAL is returned. A read from the signalfd can also return -ERESTARTSYS in case a signal hits the process. The format of the struct signalfd_siginfo is, and the valid fields depends of the (->code & __SI_MASK) value, in the same way a struct siginfo would: struct signalfd_siginfo { __u32 signo; /* si_signo */ __s32 err; /* si_errno */ __s32 code; /* si_code */ __u32 pid; /* si_pid */ __u32 uid; /* si_uid */ __s32 fd; /* si_fd */ __u32 tid; /* si_fd */ __u32 band; /* si_band */ __u32 overrun; /* si_overrun */ __u32 trapno; /* si_trapno */ __s32 status; /* si_status */ __s32 svint; /* si_int */ __u64 svptr; /* si_ptr */ __u64 utime; /* si_utime */ __u64 stime; /* si_stime */ __u64 addr; /* si_addr */ }; [akpm@linux-foundation.org: fix signalfd_copyinfo() on i386] Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-11 05:23:13 +00:00
int next_signal(struct sigpending *pending, sigset_t *mask)
{
unsigned long i, *s, *m, x;
int sig = 0;
s = pending->signal.sig;
m = mask->sig;
/*
* Handle the first word specially: it contains the
* synchronous signals that need to be dequeued first.
*/
x = *s &~ *m;
if (x) {
if (x & SYNCHRONOUS_MASK)
x &= SYNCHRONOUS_MASK;
sig = ffz(~x) + 1;
return sig;
}
switch (_NSIG_WORDS) {
default:
for (i = 1; i < _NSIG_WORDS; ++i) {
x = *++s &~ *++m;
if (!x)
continue;
sig = ffz(~x) + i*_NSIG_BPW + 1;
break;
}
break;
case 2:
x = s[1] &~ m[1];
if (!x)
break;
sig = ffz(~x) + _NSIG_BPW + 1;
break;
case 1:
/* Nothing to do */
break;
}
return sig;
}
static inline void print_dropped_signal(int sig)
{
static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
if (!print_fatal_signals)
return;
if (!__ratelimit(&ratelimit_state))
return;
pr_info("%s/%d: reached RLIMIT_SIGPENDING, dropped signal %d\n",
current->comm, current->pid, sig);
}
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
/**
* task_set_jobctl_pending - set jobctl pending bits
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
* @task: target task
* @mask: pending bits to set
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
*
* Clear @mask from @task->jobctl. @mask must be subset of
* %JOBCTL_PENDING_MASK | %JOBCTL_STOP_CONSUME | %JOBCTL_STOP_SIGMASK |
* %JOBCTL_TRAPPING. If stop signo is being set, the existing signo is
* cleared. If @task is already being killed or exiting, this function
* becomes noop.
*
* CONTEXT:
* Must be called with @task->sighand->siglock held.
*
* RETURNS:
* %true if @mask is set, %false if made noop because @task was dying.
*/
bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask)
{
BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME |
JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING));
BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK));
if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING)))
return false;
if (mask & JOBCTL_STOP_SIGMASK)
task->jobctl &= ~JOBCTL_STOP_SIGMASK;
task->jobctl |= mask;
return true;
}
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
/**
* task_clear_jobctl_trapping - clear jobctl trapping bit
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
* @task: target task
*
* If JOBCTL_TRAPPING is set, a ptracer is waiting for us to enter TRACED.
* Clear it and wake up the ptracer. Note that we don't need any further
* locking. @task->siglock guarantees that @task->parent points to the
* ptracer.
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
*
* CONTEXT:
* Must be called with @task->sighand->siglock held.
*/
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
void task_clear_jobctl_trapping(struct task_struct *task)
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
{
if (unlikely(task->jobctl & JOBCTL_TRAPPING)) {
task->jobctl &= ~JOBCTL_TRAPPING;
smp_mb(); /* advised by wake_up_bit() */
wake_up_bit(&task->jobctl, JOBCTL_TRAPPING_BIT);
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
}
}
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
/**
* task_clear_jobctl_pending - clear jobctl pending bits
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
* @task: target task
* @mask: pending bits to clear
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
*
* Clear @mask from @task->jobctl. @mask must be subset of
* %JOBCTL_PENDING_MASK. If %JOBCTL_STOP_PENDING is being cleared, other
* STOP bits are cleared together.
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
*
* If clearing of @mask leaves no stop or trap pending, this function calls
* task_clear_jobctl_trapping().
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
*
* CONTEXT:
* Must be called with @task->sighand->siglock held.
*/
void task_clear_jobctl_pending(struct task_struct *task, unsigned long mask)
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
{
BUG_ON(mask & ~JOBCTL_PENDING_MASK);
if (mask & JOBCTL_STOP_PENDING)
mask |= JOBCTL_STOP_CONSUME | JOBCTL_STOP_DEQUEUED;
task->jobctl &= ~mask;
if (!(task->jobctl & JOBCTL_PENDING_MASK))
task_clear_jobctl_trapping(task);
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
}
/**
* task_participate_group_stop - participate in a group stop
* @task: task participating in a group stop
*
* @task has %JOBCTL_STOP_PENDING set and is participating in a group stop.
signal: Use GROUP_STOP_PENDING to stop once for a single group stop Currently task->signal->group_stop_count is used to decide whether to stop for group stop. However, if there is a task in the group which is taking a long time to stop, other tasks which are continued by ptrace would repeatedly stop for the same group stop until the group stop is complete. Conversely, if a ptraced task is in TASK_TRACED state, the debugger won't get notified of group stops which is inconsistent compared to the ptraced task in any other state. This patch introduces GROUP_STOP_PENDING which tracks whether a task is yet to stop for the group stop in progress. The flag is set when a group stop starts and cleared when the task stops the first time for the group stop, and consulted whenever whether the task should participate in a group stop needs to be determined. Note that now tasks in TASK_TRACED also participate in group stop. This results in the following behavior changes. * For a single group stop, a ptracer would see at most one stop reported. * A ptracee in TASK_TRACED now also participates in group stop and the tracer would get the notification. However, as a ptraced task could be in TASK_STOPPED state or any ptrace trap could consume group stop, the notification may still be missing. These will be addressed with further patches. * A ptracee may start a group stop while one is still in progress if the tracer let it continue with stop signal delivery. Group stop code handles this correctly. Oleg: * Spotted that a task might skip signal check even when its GROUP_STOP_PENDING is set. Fixed by updating recalc_sigpending_tsk() to check GROUP_STOP_PENDING instead of group_stop_count. * Pointed out that task->group_stop should be cleared whenever task->signal->group_stop_count is cleared. Fixed accordingly. * Pointed out the behavior inconsistency between TASK_TRACED and RUNNING and the last behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
* Group stop states are cleared and the group stop count is consumed if
* %JOBCTL_STOP_CONSUME was set. If the consumption completes the group
signal: Use GROUP_STOP_PENDING to stop once for a single group stop Currently task->signal->group_stop_count is used to decide whether to stop for group stop. However, if there is a task in the group which is taking a long time to stop, other tasks which are continued by ptrace would repeatedly stop for the same group stop until the group stop is complete. Conversely, if a ptraced task is in TASK_TRACED state, the debugger won't get notified of group stops which is inconsistent compared to the ptraced task in any other state. This patch introduces GROUP_STOP_PENDING which tracks whether a task is yet to stop for the group stop in progress. The flag is set when a group stop starts and cleared when the task stops the first time for the group stop, and consulted whenever whether the task should participate in a group stop needs to be determined. Note that now tasks in TASK_TRACED also participate in group stop. This results in the following behavior changes. * For a single group stop, a ptracer would see at most one stop reported. * A ptracee in TASK_TRACED now also participates in group stop and the tracer would get the notification. However, as a ptraced task could be in TASK_STOPPED state or any ptrace trap could consume group stop, the notification may still be missing. These will be addressed with further patches. * A ptracee may start a group stop while one is still in progress if the tracer let it continue with stop signal delivery. Group stop code handles this correctly. Oleg: * Spotted that a task might skip signal check even when its GROUP_STOP_PENDING is set. Fixed by updating recalc_sigpending_tsk() to check GROUP_STOP_PENDING instead of group_stop_count. * Pointed out that task->group_stop should be cleared whenever task->signal->group_stop_count is cleared. Fixed accordingly. * Pointed out the behavior inconsistency between TASK_TRACED and RUNNING and the last behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
* stop, the appropriate %SIGNAL_* flags are set.
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
*
* CONTEXT:
* Must be called with @task->sighand->siglock held.
job control: Don't send duplicate job control stop notification while ptraced Just as group_exit_code shouldn't be generated when a PTRACE_CONT'd task re-enters job control stop, notifiction for the event should be suppressed too. The logic is the same as the group_exit_code generation suppression in do_signal_stop(), if SIGNAL_STOP_STOPPED is already set, the task is re-entering job control stop without intervening SIGCONT and the notifications should be suppressed. Test case follows. #include <stdio.h> #include <unistd.h> #include <signal.h> #include <time.h> #include <sys/ptrace.h> #include <sys/wait.h> static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static pid_t tracee, tracer; static const char *pid_who(pid_t pid) { return pid == tracee ? "tracee" : (pid == tracer ? "tracer" : "mommy "); } static void sigchld_sigaction(int signo, siginfo_t *si, void *ucxt) { printf("%s: SIG status=%02d code=%02d (%s)\n", pid_who(getpid()), si->si_status, si->si_code, pid_who(si->si_pid)); } int main(void) { const struct sigaction chld_sa = { .sa_sigaction = sigchld_sigaction, .sa_flags = SA_SIGINFO|SA_RESTART }; siginfo_t si; sigaction(SIGCHLD, &chld_sa, NULL); tracee = fork(); if (!tracee) { tracee = getpid(); while (1) pause(); } kill(tracee, SIGSTOP); waitid(P_PID, tracee, &si, WSTOPPED); tracer = fork(); if (!tracer) { tracer = getpid(); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); printf("tracer: detaching\n"); ptrace(PTRACE_DETACH, tracee, NULL, NULL); return 0; } while (1) pause(); return 0; } Before the patch, the parent gets the second notification for the tracee after the tracer detaches. si_status is zero because group_exit_code is not set by the group stop completion which triggered this notification. mommy : SIG status=19 code=05 (tracee) tracer: SIG status=00 code=05 (tracee) tracer: SIG status=19 code=04 (tracee) tracer: SIG status=00 code=05 (tracee) tracer: detaching mommy : SIG status=00 code=05 (tracee) mommy : SIG status=00 code=01 (tracer) ^C After the patch, the duplicate notification is gone. mommy : SIG status=19 code=05 (tracee) tracer: SIG status=00 code=05 (tracee) tracer: SIG status=19 code=04 (tracee) tracer: SIG status=00 code=05 (tracee) tracer: detaching mommy : SIG status=00 code=01 (tracer) ^C Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
*
* RETURNS:
* %true if group stop completion should be notified to the parent, %false
* otherwise.
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
*/
static bool task_participate_group_stop(struct task_struct *task)
{
struct signal_struct *sig = task->signal;
bool consume = task->jobctl & JOBCTL_STOP_CONSUME;
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
WARN_ON_ONCE(!(task->jobctl & JOBCTL_STOP_PENDING));
signal: Use GROUP_STOP_PENDING to stop once for a single group stop Currently task->signal->group_stop_count is used to decide whether to stop for group stop. However, if there is a task in the group which is taking a long time to stop, other tasks which are continued by ptrace would repeatedly stop for the same group stop until the group stop is complete. Conversely, if a ptraced task is in TASK_TRACED state, the debugger won't get notified of group stops which is inconsistent compared to the ptraced task in any other state. This patch introduces GROUP_STOP_PENDING which tracks whether a task is yet to stop for the group stop in progress. The flag is set when a group stop starts and cleared when the task stops the first time for the group stop, and consulted whenever whether the task should participate in a group stop needs to be determined. Note that now tasks in TASK_TRACED also participate in group stop. This results in the following behavior changes. * For a single group stop, a ptracer would see at most one stop reported. * A ptracee in TASK_TRACED now also participates in group stop and the tracer would get the notification. However, as a ptraced task could be in TASK_STOPPED state or any ptrace trap could consume group stop, the notification may still be missing. These will be addressed with further patches. * A ptracee may start a group stop while one is still in progress if the tracer let it continue with stop signal delivery. Group stop code handles this correctly. Oleg: * Spotted that a task might skip signal check even when its GROUP_STOP_PENDING is set. Fixed by updating recalc_sigpending_tsk() to check GROUP_STOP_PENDING instead of group_stop_count. * Pointed out that task->group_stop should be cleared whenever task->signal->group_stop_count is cleared. Fixed accordingly. * Pointed out the behavior inconsistency between TASK_TRACED and RUNNING and the last behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
task_clear_jobctl_pending(task, JOBCTL_STOP_PENDING);
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
if (!consume)
return false;
if (!WARN_ON_ONCE(sig->group_stop_count == 0))
sig->group_stop_count--;
job control: Don't send duplicate job control stop notification while ptraced Just as group_exit_code shouldn't be generated when a PTRACE_CONT'd task re-enters job control stop, notifiction for the event should be suppressed too. The logic is the same as the group_exit_code generation suppression in do_signal_stop(), if SIGNAL_STOP_STOPPED is already set, the task is re-entering job control stop without intervening SIGCONT and the notifications should be suppressed. Test case follows. #include <stdio.h> #include <unistd.h> #include <signal.h> #include <time.h> #include <sys/ptrace.h> #include <sys/wait.h> static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static pid_t tracee, tracer; static const char *pid_who(pid_t pid) { return pid == tracee ? "tracee" : (pid == tracer ? "tracer" : "mommy "); } static void sigchld_sigaction(int signo, siginfo_t *si, void *ucxt) { printf("%s: SIG status=%02d code=%02d (%s)\n", pid_who(getpid()), si->si_status, si->si_code, pid_who(si->si_pid)); } int main(void) { const struct sigaction chld_sa = { .sa_sigaction = sigchld_sigaction, .sa_flags = SA_SIGINFO|SA_RESTART }; siginfo_t si; sigaction(SIGCHLD, &chld_sa, NULL); tracee = fork(); if (!tracee) { tracee = getpid(); while (1) pause(); } kill(tracee, SIGSTOP); waitid(P_PID, tracee, &si, WSTOPPED); tracer = fork(); if (!tracer) { tracer = getpid(); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); printf("tracer: detaching\n"); ptrace(PTRACE_DETACH, tracee, NULL, NULL); return 0; } while (1) pause(); return 0; } Before the patch, the parent gets the second notification for the tracee after the tracer detaches. si_status is zero because group_exit_code is not set by the group stop completion which triggered this notification. mommy : SIG status=19 code=05 (tracee) tracer: SIG status=00 code=05 (tracee) tracer: SIG status=19 code=04 (tracee) tracer: SIG status=00 code=05 (tracee) tracer: detaching mommy : SIG status=00 code=05 (tracee) mommy : SIG status=00 code=01 (tracer) ^C After the patch, the duplicate notification is gone. mommy : SIG status=19 code=05 (tracee) tracer: SIG status=00 code=05 (tracee) tracer: SIG status=19 code=04 (tracee) tracer: SIG status=00 code=05 (tracee) tracer: detaching mommy : SIG status=00 code=01 (tracer) ^C Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
/*
* Tell the caller to notify completion iff we are entering into a
* fresh group stop. Read comment in do_signal_stop() for details.
*/
if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) {
signal_set_stop_flags(sig, SIGNAL_STOP_STOPPED);
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
return true;
}
return false;
}
/*
* allocate a new signal queue record
* - this may be called without locks if and only if t == current, otherwise an
* appropriate lock must be held to stop the target task from exiting
*/
static struct sigqueue *
__sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
{
struct sigqueue *q = NULL;
struct user_struct *user;
/*
* Protect access to @t credentials. This can go away when all
* callers hold rcu read lock.
*/
rcu_read_lock();
CRED: Inaugurate COW credentials Inaugurate copy-on-write credentials management. This uses RCU to manage the credentials pointer in the task_struct with respect to accesses by other tasks. A process may only modify its own credentials, and so does not need locking to access or modify its own credentials. A mutex (cred_replace_mutex) is added to the task_struct to control the effect of PTRACE_ATTACHED on credential calculations, particularly with respect to execve(). With this patch, the contents of an active credentials struct may not be changed directly; rather a new set of credentials must be prepared, modified and committed using something like the following sequence of events: struct cred *new = prepare_creds(); int ret = blah(new); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); There are some exceptions to this rule: the keyrings pointed to by the active credentials may be instantiated - keyrings violate the COW rule as managing COW keyrings is tricky, given that it is possible for a task to directly alter the keys in a keyring in use by another task. To help enforce this, various pointers to sets of credentials, such as those in the task_struct, are declared const. The purpose of this is compile-time discouragement of altering credentials through those pointers. Once a set of credentials has been made public through one of these pointers, it may not be modified, except under special circumstances: (1) Its reference count may incremented and decremented. (2) The keyrings to which it points may be modified, but not replaced. The only safe way to modify anything else is to create a replacement and commit using the functions described in Documentation/credentials.txt (which will be added by a later patch). This patch and the preceding patches have been tested with the LTP SELinux testsuite. This patch makes several logical sets of alteration: (1) execve(). This now prepares and commits credentials in various places in the security code rather than altering the current creds directly. (2) Temporary credential overrides. do_coredump() and sys_faccessat() now prepare their own credentials and temporarily override the ones currently on the acting thread, whilst preventing interference from other threads by holding cred_replace_mutex on the thread being dumped. This will be replaced in a future patch by something that hands down the credentials directly to the functions being called, rather than altering the task's objective credentials. (3) LSM interface. A number of functions have been changed, added or removed: (*) security_capset_check(), ->capset_check() (*) security_capset_set(), ->capset_set() Removed in favour of security_capset(). (*) security_capset(), ->capset() New. This is passed a pointer to the new creds, a pointer to the old creds and the proposed capability sets. It should fill in the new creds or return an error. All pointers, barring the pointer to the new creds, are now const. (*) security_bprm_apply_creds(), ->bprm_apply_creds() Changed; now returns a value, which will cause the process to be killed if it's an error. (*) security_task_alloc(), ->task_alloc_security() Removed in favour of security_prepare_creds(). (*) security_cred_free(), ->cred_free() New. Free security data attached to cred->security. (*) security_prepare_creds(), ->cred_prepare() New. Duplicate any security data attached to cred->security. (*) security_commit_creds(), ->cred_commit() New. Apply any security effects for the upcoming installation of new security by commit_creds(). (*) security_task_post_setuid(), ->task_post_setuid() Removed in favour of security_task_fix_setuid(). (*) security_task_fix_setuid(), ->task_fix_setuid() Fix up the proposed new credentials for setuid(). This is used by cap_set_fix_setuid() to implicitly adjust capabilities in line with setuid() changes. Changes are made to the new credentials, rather than the task itself as in security_task_post_setuid(). (*) security_task_reparent_to_init(), ->task_reparent_to_init() Removed. Instead the task being reparented to init is referred directly to init's credentials. NOTE! This results in the loss of some state: SELinux's osid no longer records the sid of the thread that forked it. (*) security_key_alloc(), ->key_alloc() (*) security_key_permission(), ->key_permission() Changed. These now take cred pointers rather than task pointers to refer to the security context. (4) sys_capset(). This has been simplified and uses less locking. The LSM functions it calls have been merged. (5) reparent_to_kthreadd(). This gives the current thread the same credentials as init by simply using commit_thread() to point that way. (6) __sigqueue_alloc() and switch_uid() __sigqueue_alloc() can't stop the target task from changing its creds beneath it, so this function gets a reference to the currently applicable user_struct which it then passes into the sigqueue struct it returns if successful. switch_uid() is now called from commit_creds(), and possibly should be folded into that. commit_creds() should take care of protecting __sigqueue_alloc(). (7) [sg]et[ug]id() and co and [sg]et_current_groups. The set functions now all use prepare_creds(), commit_creds() and abort_creds() to build and check a new set of credentials before applying it. security_task_set[ug]id() is called inside the prepared section. This guarantees that nothing else will affect the creds until we've finished. The calling of set_dumpable() has been moved into commit_creds(). Much of the functionality of set_user() has been moved into commit_creds(). The get functions all simply access the data directly. (8) security_task_prctl() and cap_task_prctl(). security_task_prctl() has been modified to return -ENOSYS if it doesn't want to handle a function, or otherwise return the return value directly rather than through an argument. Additionally, cap_task_prctl() now prepares a new set of credentials, even if it doesn't end up using it. (9) Keyrings. A number of changes have been made to the keyrings code: (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have all been dropped and built in to the credentials functions directly. They may want separating out again later. (b) key_alloc() and search_process_keyrings() now take a cred pointer rather than a task pointer to specify the security context. (c) copy_creds() gives a new thread within the same thread group a new thread keyring if its parent had one, otherwise it discards the thread keyring. (d) The authorisation key now points directly to the credentials to extend the search into rather pointing to the task that carries them. (e) Installing thread, process or session keyrings causes a new set of credentials to be created, even though it's not strictly necessary for process or session keyrings (they're shared). (10) Usermode helper. The usermode helper code now carries a cred struct pointer in its subprocess_info struct instead of a new session keyring pointer. This set of credentials is derived from init_cred and installed on the new process after it has been cloned. call_usermodehelper_setup() allocates the new credentials and call_usermodehelper_freeinfo() discards them if they haven't been used. A special cred function (prepare_usermodeinfo_creds()) is provided specifically for call_usermodehelper_setup() to call. call_usermodehelper_setkeys() adjusts the credentials to sport the supplied keyring as the new session keyring. (11) SELinux. SELinux has a number of changes, in addition to those to support the LSM interface changes mentioned above: (a) selinux_setprocattr() no longer does its check for whether the current ptracer can access processes with the new SID inside the lock that covers getting the ptracer's SID. Whilst this lock ensures that the check is done with the ptracer pinned, the result is only valid until the lock is released, so there's no point doing it inside the lock. (12) is_single_threaded(). This function has been extracted from selinux_setprocattr() and put into a file of its own in the lib/ directory as join_session_keyring() now wants to use it too. The code in SELinux just checked to see whether a task shared mm_structs with other tasks (CLONE_VM), but that isn't good enough. We really want to know if they're part of the same thread group (CLONE_THREAD). (13) nfsd. The NFS server daemon now has to use the COW credentials to set the credentials it is going to use. It really needs to pass the credentials down to the functions it calls, but it can't do that until other patches in this series have been applied. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: James Morris <jmorris@namei.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-11-13 23:39:23 +00:00
user = get_uid(__task_cred(t)->user);
atomic_inc(&user->sigpending);
rcu_read_unlock();
if (override_rlimit ||
atomic_read(&user->sigpending) <=
task_rlimit(t, RLIMIT_SIGPENDING)) {
q = kmem_cache_alloc(sigqueue_cachep, flags);
} else {
print_dropped_signal(sig);
}
if (unlikely(q == NULL)) {
atomic_dec(&user->sigpending);
CRED: Inaugurate COW credentials Inaugurate copy-on-write credentials management. This uses RCU to manage the credentials pointer in the task_struct with respect to accesses by other tasks. A process may only modify its own credentials, and so does not need locking to access or modify its own credentials. A mutex (cred_replace_mutex) is added to the task_struct to control the effect of PTRACE_ATTACHED on credential calculations, particularly with respect to execve(). With this patch, the contents of an active credentials struct may not be changed directly; rather a new set of credentials must be prepared, modified and committed using something like the following sequence of events: struct cred *new = prepare_creds(); int ret = blah(new); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); There are some exceptions to this rule: the keyrings pointed to by the active credentials may be instantiated - keyrings violate the COW rule as managing COW keyrings is tricky, given that it is possible for a task to directly alter the keys in a keyring in use by another task. To help enforce this, various pointers to sets of credentials, such as those in the task_struct, are declared const. The purpose of this is compile-time discouragement of altering credentials through those pointers. Once a set of credentials has been made public through one of these pointers, it may not be modified, except under special circumstances: (1) Its reference count may incremented and decremented. (2) The keyrings to which it points may be modified, but not replaced. The only safe way to modify anything else is to create a replacement and commit using the functions described in Documentation/credentials.txt (which will be added by a later patch). This patch and the preceding patches have been tested with the LTP SELinux testsuite. This patch makes several logical sets of alteration: (1) execve(). This now prepares and commits credentials in various places in the security code rather than altering the current creds directly. (2) Temporary credential overrides. do_coredump() and sys_faccessat() now prepare their own credentials and temporarily override the ones currently on the acting thread, whilst preventing interference from other threads by holding cred_replace_mutex on the thread being dumped. This will be replaced in a future patch by something that hands down the credentials directly to the functions being called, rather than altering the task's objective credentials. (3) LSM interface. A number of functions have been changed, added or removed: (*) security_capset_check(), ->capset_check() (*) security_capset_set(), ->capset_set() Removed in favour of security_capset(). (*) security_capset(), ->capset() New. This is passed a pointer to the new creds, a pointer to the old creds and the proposed capability sets. It should fill in the new creds or return an error. All pointers, barring the pointer to the new creds, are now const. (*) security_bprm_apply_creds(), ->bprm_apply_creds() Changed; now returns a value, which will cause the process to be killed if it's an error. (*) security_task_alloc(), ->task_alloc_security() Removed in favour of security_prepare_creds(). (*) security_cred_free(), ->cred_free() New. Free security data attached to cred->security. (*) security_prepare_creds(), ->cred_prepare() New. Duplicate any security data attached to cred->security. (*) security_commit_creds(), ->cred_commit() New. Apply any security effects for the upcoming installation of new security by commit_creds(). (*) security_task_post_setuid(), ->task_post_setuid() Removed in favour of security_task_fix_setuid(). (*) security_task_fix_setuid(), ->task_fix_setuid() Fix up the proposed new credentials for setuid(). This is used by cap_set_fix_setuid() to implicitly adjust capabilities in line with setuid() changes. Changes are made to the new credentials, rather than the task itself as in security_task_post_setuid(). (*) security_task_reparent_to_init(), ->task_reparent_to_init() Removed. Instead the task being reparented to init is referred directly to init's credentials. NOTE! This results in the loss of some state: SELinux's osid no longer records the sid of the thread that forked it. (*) security_key_alloc(), ->key_alloc() (*) security_key_permission(), ->key_permission() Changed. These now take cred pointers rather than task pointers to refer to the security context. (4) sys_capset(). This has been simplified and uses less locking. The LSM functions it calls have been merged. (5) reparent_to_kthreadd(). This gives the current thread the same credentials as init by simply using commit_thread() to point that way. (6) __sigqueue_alloc() and switch_uid() __sigqueue_alloc() can't stop the target task from changing its creds beneath it, so this function gets a reference to the currently applicable user_struct which it then passes into the sigqueue struct it returns if successful. switch_uid() is now called from commit_creds(), and possibly should be folded into that. commit_creds() should take care of protecting __sigqueue_alloc(). (7) [sg]et[ug]id() and co and [sg]et_current_groups. The set functions now all use prepare_creds(), commit_creds() and abort_creds() to build and check a new set of credentials before applying it. security_task_set[ug]id() is called inside the prepared section. This guarantees that nothing else will affect the creds until we've finished. The calling of set_dumpable() has been moved into commit_creds(). Much of the functionality of set_user() has been moved into commit_creds(). The get functions all simply access the data directly. (8) security_task_prctl() and cap_task_prctl(). security_task_prctl() has been modified to return -ENOSYS if it doesn't want to handle a function, or otherwise return the return value directly rather than through an argument. Additionally, cap_task_prctl() now prepares a new set of credentials, even if it doesn't end up using it. (9) Keyrings. A number of changes have been made to the keyrings code: (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have all been dropped and built in to the credentials functions directly. They may want separating out again later. (b) key_alloc() and search_process_keyrings() now take a cred pointer rather than a task pointer to specify the security context. (c) copy_creds() gives a new thread within the same thread group a new thread keyring if its parent had one, otherwise it discards the thread keyring. (d) The authorisation key now points directly to the credentials to extend the search into rather pointing to the task that carries them. (e) Installing thread, process or session keyrings causes a new set of credentials to be created, even though it's not strictly necessary for process or session keyrings (they're shared). (10) Usermode helper. The usermode helper code now carries a cred struct pointer in its subprocess_info struct instead of a new session keyring pointer. This set of credentials is derived from init_cred and installed on the new process after it has been cloned. call_usermodehelper_setup() allocates the new credentials and call_usermodehelper_freeinfo() discards them if they haven't been used. A special cred function (prepare_usermodeinfo_creds()) is provided specifically for call_usermodehelper_setup() to call. call_usermodehelper_setkeys() adjusts the credentials to sport the supplied keyring as the new session keyring. (11) SELinux. SELinux has a number of changes, in addition to those to support the LSM interface changes mentioned above: (a) selinux_setprocattr() no longer does its check for whether the current ptracer can access processes with the new SID inside the lock that covers getting the ptracer's SID. Whilst this lock ensures that the check is done with the ptracer pinned, the result is only valid until the lock is released, so there's no point doing it inside the lock. (12) is_single_threaded(). This function has been extracted from selinux_setprocattr() and put into a file of its own in the lib/ directory as join_session_keyring() now wants to use it too. The code in SELinux just checked to see whether a task shared mm_structs with other tasks (CLONE_VM), but that isn't good enough. We really want to know if they're part of the same thread group (CLONE_THREAD). (13) nfsd. The NFS server daemon now has to use the COW credentials to set the credentials it is going to use. It really needs to pass the credentials down to the functions it calls, but it can't do that until other patches in this series have been applied. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: James Morris <jmorris@namei.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-11-13 23:39:23 +00:00
free_uid(user);
} else {
INIT_LIST_HEAD(&q->list);
q->flags = 0;
CRED: Inaugurate COW credentials Inaugurate copy-on-write credentials management. This uses RCU to manage the credentials pointer in the task_struct with respect to accesses by other tasks. A process may only modify its own credentials, and so does not need locking to access or modify its own credentials. A mutex (cred_replace_mutex) is added to the task_struct to control the effect of PTRACE_ATTACHED on credential calculations, particularly with respect to execve(). With this patch, the contents of an active credentials struct may not be changed directly; rather a new set of credentials must be prepared, modified and committed using something like the following sequence of events: struct cred *new = prepare_creds(); int ret = blah(new); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); There are some exceptions to this rule: the keyrings pointed to by the active credentials may be instantiated - keyrings violate the COW rule as managing COW keyrings is tricky, given that it is possible for a task to directly alter the keys in a keyring in use by another task. To help enforce this, various pointers to sets of credentials, such as those in the task_struct, are declared const. The purpose of this is compile-time discouragement of altering credentials through those pointers. Once a set of credentials has been made public through one of these pointers, it may not be modified, except under special circumstances: (1) Its reference count may incremented and decremented. (2) The keyrings to which it points may be modified, but not replaced. The only safe way to modify anything else is to create a replacement and commit using the functions described in Documentation/credentials.txt (which will be added by a later patch). This patch and the preceding patches have been tested with the LTP SELinux testsuite. This patch makes several logical sets of alteration: (1) execve(). This now prepares and commits credentials in various places in the security code rather than altering the current creds directly. (2) Temporary credential overrides. do_coredump() and sys_faccessat() now prepare their own credentials and temporarily override the ones currently on the acting thread, whilst preventing interference from other threads by holding cred_replace_mutex on the thread being dumped. This will be replaced in a future patch by something that hands down the credentials directly to the functions being called, rather than altering the task's objective credentials. (3) LSM interface. A number of functions have been changed, added or removed: (*) security_capset_check(), ->capset_check() (*) security_capset_set(), ->capset_set() Removed in favour of security_capset(). (*) security_capset(), ->capset() New. This is passed a pointer to the new creds, a pointer to the old creds and the proposed capability sets. It should fill in the new creds or return an error. All pointers, barring the pointer to the new creds, are now const. (*) security_bprm_apply_creds(), ->bprm_apply_creds() Changed; now returns a value, which will cause the process to be killed if it's an error. (*) security_task_alloc(), ->task_alloc_security() Removed in favour of security_prepare_creds(). (*) security_cred_free(), ->cred_free() New. Free security data attached to cred->security. (*) security_prepare_creds(), ->cred_prepare() New. Duplicate any security data attached to cred->security. (*) security_commit_creds(), ->cred_commit() New. Apply any security effects for the upcoming installation of new security by commit_creds(). (*) security_task_post_setuid(), ->task_post_setuid() Removed in favour of security_task_fix_setuid(). (*) security_task_fix_setuid(), ->task_fix_setuid() Fix up the proposed new credentials for setuid(). This is used by cap_set_fix_setuid() to implicitly adjust capabilities in line with setuid() changes. Changes are made to the new credentials, rather than the task itself as in security_task_post_setuid(). (*) security_task_reparent_to_init(), ->task_reparent_to_init() Removed. Instead the task being reparented to init is referred directly to init's credentials. NOTE! This results in the loss of some state: SELinux's osid no longer records the sid of the thread that forked it. (*) security_key_alloc(), ->key_alloc() (*) security_key_permission(), ->key_permission() Changed. These now take cred pointers rather than task pointers to refer to the security context. (4) sys_capset(). This has been simplified and uses less locking. The LSM functions it calls have been merged. (5) reparent_to_kthreadd(). This gives the current thread the same credentials as init by simply using commit_thread() to point that way. (6) __sigqueue_alloc() and switch_uid() __sigqueue_alloc() can't stop the target task from changing its creds beneath it, so this function gets a reference to the currently applicable user_struct which it then passes into the sigqueue struct it returns if successful. switch_uid() is now called from commit_creds(), and possibly should be folded into that. commit_creds() should take care of protecting __sigqueue_alloc(). (7) [sg]et[ug]id() and co and [sg]et_current_groups. The set functions now all use prepare_creds(), commit_creds() and abort_creds() to build and check a new set of credentials before applying it. security_task_set[ug]id() is called inside the prepared section. This guarantees that nothing else will affect the creds until we've finished. The calling of set_dumpable() has been moved into commit_creds(). Much of the functionality of set_user() has been moved into commit_creds(). The get functions all simply access the data directly. (8) security_task_prctl() and cap_task_prctl(). security_task_prctl() has been modified to return -ENOSYS if it doesn't want to handle a function, or otherwise return the return value directly rather than through an argument. Additionally, cap_task_prctl() now prepares a new set of credentials, even if it doesn't end up using it. (9) Keyrings. A number of changes have been made to the keyrings code: (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have all been dropped and built in to the credentials functions directly. They may want separating out again later. (b) key_alloc() and search_process_keyrings() now take a cred pointer rather than a task pointer to specify the security context. (c) copy_creds() gives a new thread within the same thread group a new thread keyring if its parent had one, otherwise it discards the thread keyring. (d) The authorisation key now points directly to the credentials to extend the search into rather pointing to the task that carries them. (e) Installing thread, process or session keyrings causes a new set of credentials to be created, even though it's not strictly necessary for process or session keyrings (they're shared). (10) Usermode helper. The usermode helper code now carries a cred struct pointer in its subprocess_info struct instead of a new session keyring pointer. This set of credentials is derived from init_cred and installed on the new process after it has been cloned. call_usermodehelper_setup() allocates the new credentials and call_usermodehelper_freeinfo() discards them if they haven't been used. A special cred function (prepare_usermodeinfo_creds()) is provided specifically for call_usermodehelper_setup() to call. call_usermodehelper_setkeys() adjusts the credentials to sport the supplied keyring as the new session keyring. (11) SELinux. SELinux has a number of changes, in addition to those to support the LSM interface changes mentioned above: (a) selinux_setprocattr() no longer does its check for whether the current ptracer can access processes with the new SID inside the lock that covers getting the ptracer's SID. Whilst this lock ensures that the check is done with the ptracer pinned, the result is only valid until the lock is released, so there's no point doing it inside the lock. (12) is_single_threaded(). This function has been extracted from selinux_setprocattr() and put into a file of its own in the lib/ directory as join_session_keyring() now wants to use it too. The code in SELinux just checked to see whether a task shared mm_structs with other tasks (CLONE_VM), but that isn't good enough. We really want to know if they're part of the same thread group (CLONE_THREAD). (13) nfsd. The NFS server daemon now has to use the COW credentials to set the credentials it is going to use. It really needs to pass the credentials down to the functions it calls, but it can't do that until other patches in this series have been applied. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: James Morris <jmorris@namei.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-11-13 23:39:23 +00:00
q->user = user;
}
CRED: Inaugurate COW credentials Inaugurate copy-on-write credentials management. This uses RCU to manage the credentials pointer in the task_struct with respect to accesses by other tasks. A process may only modify its own credentials, and so does not need locking to access or modify its own credentials. A mutex (cred_replace_mutex) is added to the task_struct to control the effect of PTRACE_ATTACHED on credential calculations, particularly with respect to execve(). With this patch, the contents of an active credentials struct may not be changed directly; rather a new set of credentials must be prepared, modified and committed using something like the following sequence of events: struct cred *new = prepare_creds(); int ret = blah(new); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); There are some exceptions to this rule: the keyrings pointed to by the active credentials may be instantiated - keyrings violate the COW rule as managing COW keyrings is tricky, given that it is possible for a task to directly alter the keys in a keyring in use by another task. To help enforce this, various pointers to sets of credentials, such as those in the task_struct, are declared const. The purpose of this is compile-time discouragement of altering credentials through those pointers. Once a set of credentials has been made public through one of these pointers, it may not be modified, except under special circumstances: (1) Its reference count may incremented and decremented. (2) The keyrings to which it points may be modified, but not replaced. The only safe way to modify anything else is to create a replacement and commit using the functions described in Documentation/credentials.txt (which will be added by a later patch). This patch and the preceding patches have been tested with the LTP SELinux testsuite. This patch makes several logical sets of alteration: (1) execve(). This now prepares and commits credentials in various places in the security code rather than altering the current creds directly. (2) Temporary credential overrides. do_coredump() and sys_faccessat() now prepare their own credentials and temporarily override the ones currently on the acting thread, whilst preventing interference from other threads by holding cred_replace_mutex on the thread being dumped. This will be replaced in a future patch by something that hands down the credentials directly to the functions being called, rather than altering the task's objective credentials. (3) LSM interface. A number of functions have been changed, added or removed: (*) security_capset_check(), ->capset_check() (*) security_capset_set(), ->capset_set() Removed in favour of security_capset(). (*) security_capset(), ->capset() New. This is passed a pointer to the new creds, a pointer to the old creds and the proposed capability sets. It should fill in the new creds or return an error. All pointers, barring the pointer to the new creds, are now const. (*) security_bprm_apply_creds(), ->bprm_apply_creds() Changed; now returns a value, which will cause the process to be killed if it's an error. (*) security_task_alloc(), ->task_alloc_security() Removed in favour of security_prepare_creds(). (*) security_cred_free(), ->cred_free() New. Free security data attached to cred->security. (*) security_prepare_creds(), ->cred_prepare() New. Duplicate any security data attached to cred->security. (*) security_commit_creds(), ->cred_commit() New. Apply any security effects for the upcoming installation of new security by commit_creds(). (*) security_task_post_setuid(), ->task_post_setuid() Removed in favour of security_task_fix_setuid(). (*) security_task_fix_setuid(), ->task_fix_setuid() Fix up the proposed new credentials for setuid(). This is used by cap_set_fix_setuid() to implicitly adjust capabilities in line with setuid() changes. Changes are made to the new credentials, rather than the task itself as in security_task_post_setuid(). (*) security_task_reparent_to_init(), ->task_reparent_to_init() Removed. Instead the task being reparented to init is referred directly to init's credentials. NOTE! This results in the loss of some state: SELinux's osid no longer records the sid of the thread that forked it. (*) security_key_alloc(), ->key_alloc() (*) security_key_permission(), ->key_permission() Changed. These now take cred pointers rather than task pointers to refer to the security context. (4) sys_capset(). This has been simplified and uses less locking. The LSM functions it calls have been merged. (5) reparent_to_kthreadd(). This gives the current thread the same credentials as init by simply using commit_thread() to point that way. (6) __sigqueue_alloc() and switch_uid() __sigqueue_alloc() can't stop the target task from changing its creds beneath it, so this function gets a reference to the currently applicable user_struct which it then passes into the sigqueue struct it returns if successful. switch_uid() is now called from commit_creds(), and possibly should be folded into that. commit_creds() should take care of protecting __sigqueue_alloc(). (7) [sg]et[ug]id() and co and [sg]et_current_groups. The set functions now all use prepare_creds(), commit_creds() and abort_creds() to build and check a new set of credentials before applying it. security_task_set[ug]id() is called inside the prepared section. This guarantees that nothing else will affect the creds until we've finished. The calling of set_dumpable() has been moved into commit_creds(). Much of the functionality of set_user() has been moved into commit_creds(). The get functions all simply access the data directly. (8) security_task_prctl() and cap_task_prctl(). security_task_prctl() has been modified to return -ENOSYS if it doesn't want to handle a function, or otherwise return the return value directly rather than through an argument. Additionally, cap_task_prctl() now prepares a new set of credentials, even if it doesn't end up using it. (9) Keyrings. A number of changes have been made to the keyrings code: (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have all been dropped and built in to the credentials functions directly. They may want separating out again later. (b) key_alloc() and search_process_keyrings() now take a cred pointer rather than a task pointer to specify the security context. (c) copy_creds() gives a new thread within the same thread group a new thread keyring if its parent had one, otherwise it discards the thread keyring. (d) The authorisation key now points directly to the credentials to extend the search into rather pointing to the task that carries them. (e) Installing thread, process or session keyrings causes a new set of credentials to be created, even though it's not strictly necessary for process or session keyrings (they're shared). (10) Usermode helper. The usermode helper code now carries a cred struct pointer in its subprocess_info struct instead of a new session keyring pointer. This set of credentials is derived from init_cred and installed on the new process after it has been cloned. call_usermodehelper_setup() allocates the new credentials and call_usermodehelper_freeinfo() discards them if they haven't been used. A special cred function (prepare_usermodeinfo_creds()) is provided specifically for call_usermodehelper_setup() to call. call_usermodehelper_setkeys() adjusts the credentials to sport the supplied keyring as the new session keyring. (11) SELinux. SELinux has a number of changes, in addition to those to support the LSM interface changes mentioned above: (a) selinux_setprocattr() no longer does its check for whether the current ptracer can access processes with the new SID inside the lock that covers getting the ptracer's SID. Whilst this lock ensures that the check is done with the ptracer pinned, the result is only valid until the lock is released, so there's no point doing it inside the lock. (12) is_single_threaded(). This function has been extracted from selinux_setprocattr() and put into a file of its own in the lib/ directory as join_session_keyring() now wants to use it too. The code in SELinux just checked to see whether a task shared mm_structs with other tasks (CLONE_VM), but that isn't good enough. We really want to know if they're part of the same thread group (CLONE_THREAD). (13) nfsd. The NFS server daemon now has to use the COW credentials to set the credentials it is going to use. It really needs to pass the credentials down to the functions it calls, but it can't do that until other patches in this series have been applied. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: James Morris <jmorris@namei.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-11-13 23:39:23 +00:00
return q;
}
static void __sigqueue_free(struct sigqueue *q)
{
if (q->flags & SIGQUEUE_PREALLOC)
return;
atomic_dec(&q->user->sigpending);
free_uid(q->user);
kmem_cache_free(sigqueue_cachep, q);
}
void flush_sigqueue(struct sigpending *queue)
{
struct sigqueue *q;
sigemptyset(&queue->signal);
while (!list_empty(&queue->list)) {
q = list_entry(queue->list.next, struct sigqueue , list);
list_del_init(&q->list);
__sigqueue_free(q);
}
}
/*
* Flush all pending signals for this kthread.
*/
void flush_signals(struct task_struct *t)
{
unsigned long flags;
spin_lock_irqsave(&t->sighand->siglock, flags);
clear_tsk_thread_flag(t, TIF_SIGPENDING);
flush_sigqueue(&t->pending);
flush_sigqueue(&t->signal->shared_pending);
spin_unlock_irqrestore(&t->sighand->siglock, flags);
}
#ifdef CONFIG_POSIX_TIMERS
static void __flush_itimer_signals(struct sigpending *pending)
{
sigset_t signal, retain;
struct sigqueue *q, *n;
signal = pending->signal;
sigemptyset(&retain);
list_for_each_entry_safe(q, n, &pending->list, list) {
int sig = q->info.si_signo;
if (likely(q->info.si_code != SI_TIMER)) {
sigaddset(&retain, sig);
} else {
sigdelset(&signal, sig);
list_del_init(&q->list);
__sigqueue_free(q);
}
}
sigorsets(&pending->signal, &signal, &retain);
}
void flush_itimer_signals(void)
{
struct task_struct *tsk = current;
unsigned long flags;
spin_lock_irqsave(&tsk->sighand->siglock, flags);
__flush_itimer_signals(&tsk->pending);
__flush_itimer_signals(&tsk->signal->shared_pending);
spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
}
#endif
void ignore_signals(struct task_struct *t)
{
int i;
for (i = 0; i < _NSIG; ++i)
t->sighand->action[i].sa.sa_handler = SIG_IGN;
flush_signals(t);
}
/*
* Flush all handlers for a task.
*/
void
flush_signal_handlers(struct task_struct *t, int force_default)
{
int i;
struct k_sigaction *ka = &t->sighand->action[0];
for (i = _NSIG ; i != 0 ; i--) {
if (force_default || ka->sa.sa_handler != SIG_IGN)
ka->sa.sa_handler = SIG_DFL;
ka->sa.sa_flags = 0;
#ifdef __ARCH_HAS_SA_RESTORER
signal: always clear sa_restorer on execve When the new signal handlers are set up, the location of sa_restorer is not cleared, leaking a parent process's address space location to children. This allows for a potential bypass of the parent's ASLR by examining the sa_restorer value returned when calling sigaction(). Based on what should be considered "secret" about addresses, it only matters across the exec not the fork (since the VMAs haven't changed until the exec). But since exec sets SIG_DFL and keeps sa_restorer, this is where it should be fixed. Given the few uses of sa_restorer, a "set" function was not written since this would be the only use. Instead, we use __ARCH_HAS_SA_RESTORER, as already done in other places. Example of the leak before applying this patch: $ cat /proc/$$/maps ... 7fb9f3083000-7fb9f3238000 r-xp 00000000 fd:01 404469 .../libc-2.15.so ... $ ./leak ... 7f278bc74000-7f278be29000 r-xp 00000000 fd:01 404469 .../libc-2.15.so ... 1 0 (nil) 0x7fb9f30b94a0 2 4000000 (nil) 0x7f278bcaa4a0 3 4000000 (nil) 0x7f278bcaa4a0 4 0 (nil) 0x7fb9f30b94a0 ... [akpm@linux-foundation.org: use SA_RESTORER for backportability] Signed-off-by: Kees Cook <keescook@chromium.org> Reported-by: Emese Revfy <re.emese@gmail.com> Cc: Emese Revfy <re.emese@gmail.com> Cc: PaX Team <pageexec@freemail.hu> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Oleg Nesterov <oleg@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Serge Hallyn <serge.hallyn@canonical.com> Cc: Julien Tinnes <jln@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-03-13 21:59:33 +00:00
ka->sa.sa_restorer = NULL;
#endif
sigemptyset(&ka->sa.sa_mask);
ka++;
}
}
int unhandled_signal(struct task_struct *tsk, int sig)
{
void __user *handler = tsk->sighand->action[sig-1].sa.sa_handler;
pid namespaces: define is_global_init() and is_container_init() is_init() is an ambiguous name for the pid==1 check. Split it into is_global_init() and is_container_init(). A cgroup init has it's tsk->pid == 1. A global init also has it's tsk->pid == 1 and it's active pid namespace is the init_pid_ns. But rather than check the active pid namespace, compare the task structure with 'init_pid_ns.child_reaper', which is initialized during boot to the /sbin/init process and never changes. Changelog: 2.6.22-rc4-mm2-pidns1: - Use 'init_pid_ns.child_reaper' to determine if a given task is the global init (/sbin/init) process. This would improve performance and remove dependence on the task_pid(). 2.6.21-mm2-pidns2: - [Sukadev Bhattiprolu] Changed is_container_init() calls in {powerpc, ppc,avr32}/traps.c for the _exception() call to is_global_init(). This way, we kill only the cgroup if the cgroup's init has a bug rather than force a kernel panic. [akpm@linux-foundation.org: fix comment] [sukadev@us.ibm.com: Use is_global_init() in arch/m32r/mm/fault.c] [bunk@stusta.de: kernel/pid.c: remove unused exports] [sukadev@us.ibm.com: Fix capability.c to work with threaded init] Signed-off-by: Serge E. Hallyn <serue@us.ibm.com> Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com> Acked-by: Pavel Emelianov <xemul@openvz.org> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Cedric Le Goater <clg@fr.ibm.com> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: Herbert Poetzel <herbert@13thfloor.at> Cc: Kirill Korotaev <dev@sw.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-19 06:39:52 +00:00
if (is_global_init(tsk))
return 1;
if (handler != SIG_IGN && handler != SIG_DFL)
return 0;
/* if ptraced, let the tracer determine */
return !tsk->ptrace;
}
signal: Only reschedule timers on signals timers have sent Thomas Gleixner wrote: > The CRIU support added a 'feature' which allows a user space task to send > arbitrary (kernel) signals to itself. The changelog says: > > The kernel prevents sending of siginfo with positive si_code, because > these codes are reserved for kernel. I think we can allow a task to > send such a siginfo to itself. This operation should not be dangerous. > > Quite contrary to that claim, it turns out that it is outright dangerous > for signals with info->si_code == SI_TIMER. The following code sequence in > a user space task allows to crash the kernel: > > id = timer_create(CLOCK_XXX, ..... signo = SIGX); > timer_set(id, ....); > info->si_signo = SIGX; > info->si_code = SI_TIMER: > info->_sifields._timer._tid = id; > info->_sifields._timer._sys_private = 2; > rt_[tg]sigqueueinfo(..., SIGX, info); > sigemptyset(&sigset); > sigaddset(&sigset, SIGX); > rt_sigtimedwait(sigset, info); > > For timers based on CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID this > results in a kernel crash because sigwait() dequeues the signal and the > dequeue code observes: > > info->si_code == SI_TIMER && info->_sifields._timer._sys_private != 0 > > which triggers the following callchain: > > do_schedule_next_timer() -> posix_cpu_timer_schedule() -> arm_timer() > > arm_timer() executes a list_add() on the timer, which is already armed via > the timer_set() syscall. That's a double list add which corrupts the posix > cpu timer list. As a consequence the kernel crashes on the next operation > touching the posix cpu timer list. > > Posix clocks which are internally implemented based on hrtimers are not > affected by this because hrtimer_start() can handle already armed timers > nicely, but it's a reliable way to trigger the WARN_ON() in > hrtimer_forward(), which complains about calling that function on an > already armed timer. This problem has existed since the posix timer code was merged into 2.5.63. A few releases earlier in 2.5.60 ptrace gained the ability to inject not just a signal (which linux has supported since 1.0) but the full siginfo of a signal. The core problem is that the code will reschedule in response to signals getting dequeued not just for signals the timers sent but for other signals that happen to a si_code of SI_TIMER. Avoid this confusion by testing to see if the queued signal was preallocated as all timer signals are preallocated, and so far only the timer code preallocates signals. Move the check for if a timer needs to be rescheduled up into collect_signal where the preallocation check must be performed, and pass the result back to dequeue_signal where the code reschedules timers. This makes it clear why the code cares about preallocated timers. Cc: stable@vger.kernel.org Reported-by: Thomas Gleixner <tglx@linutronix.de> History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reference: 66dd34ad31e5 ("signal: allow to send any siginfo to itself") Reference: 1669ce53e2ff ("Add PTRACE_GETSIGINFO and PTRACE_SETSIGINFO") Fixes: db8b50ba75f2 ("[PATCH] POSIX clocks & timers") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-06-13 09:31:16 +00:00
static void collect_signal(int sig, struct sigpending *list, siginfo_t *info,
bool *resched_timer)
{
struct sigqueue *q, *first = NULL;
/*
* Collect the siginfo appropriate to this signal. Check if
* there is another siginfo for the same signal.
*/
list_for_each_entry(q, &list->list, list) {
if (q->info.si_signo == sig) {
if (first)
goto still_pending;
first = q;
}
}
sigdelset(&list->signal, sig);
if (first) {
still_pending:
list_del_init(&first->list);
copy_siginfo(info, &first->info);
signal: Only reschedule timers on signals timers have sent Thomas Gleixner wrote: > The CRIU support added a 'feature' which allows a user space task to send > arbitrary (kernel) signals to itself. The changelog says: > > The kernel prevents sending of siginfo with positive si_code, because > these codes are reserved for kernel. I think we can allow a task to > send such a siginfo to itself. This operation should not be dangerous. > > Quite contrary to that claim, it turns out that it is outright dangerous > for signals with info->si_code == SI_TIMER. The following code sequence in > a user space task allows to crash the kernel: > > id = timer_create(CLOCK_XXX, ..... signo = SIGX); > timer_set(id, ....); > info->si_signo = SIGX; > info->si_code = SI_TIMER: > info->_sifields._timer._tid = id; > info->_sifields._timer._sys_private = 2; > rt_[tg]sigqueueinfo(..., SIGX, info); > sigemptyset(&sigset); > sigaddset(&sigset, SIGX); > rt_sigtimedwait(sigset, info); > > For timers based on CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID this > results in a kernel crash because sigwait() dequeues the signal and the > dequeue code observes: > > info->si_code == SI_TIMER && info->_sifields._timer._sys_private != 0 > > which triggers the following callchain: > > do_schedule_next_timer() -> posix_cpu_timer_schedule() -> arm_timer() > > arm_timer() executes a list_add() on the timer, which is already armed via > the timer_set() syscall. That's a double list add which corrupts the posix > cpu timer list. As a consequence the kernel crashes on the next operation > touching the posix cpu timer list. > > Posix clocks which are internally implemented based on hrtimers are not > affected by this because hrtimer_start() can handle already armed timers > nicely, but it's a reliable way to trigger the WARN_ON() in > hrtimer_forward(), which complains about calling that function on an > already armed timer. This problem has existed since the posix timer code was merged into 2.5.63. A few releases earlier in 2.5.60 ptrace gained the ability to inject not just a signal (which linux has supported since 1.0) but the full siginfo of a signal. The core problem is that the code will reschedule in response to signals getting dequeued not just for signals the timers sent but for other signals that happen to a si_code of SI_TIMER. Avoid this confusion by testing to see if the queued signal was preallocated as all timer signals are preallocated, and so far only the timer code preallocates signals. Move the check for if a timer needs to be rescheduled up into collect_signal where the preallocation check must be performed, and pass the result back to dequeue_signal where the code reschedules timers. This makes it clear why the code cares about preallocated timers. Cc: stable@vger.kernel.org Reported-by: Thomas Gleixner <tglx@linutronix.de> History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reference: 66dd34ad31e5 ("signal: allow to send any siginfo to itself") Reference: 1669ce53e2ff ("Add PTRACE_GETSIGINFO and PTRACE_SETSIGINFO") Fixes: db8b50ba75f2 ("[PATCH] POSIX clocks & timers") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-06-13 09:31:16 +00:00
*resched_timer =
(first->flags & SIGQUEUE_PREALLOC) &&
(info->si_code == SI_TIMER) &&
(info->si_sys_private);
__sigqueue_free(first);
} else {
/*
* Ok, it wasn't in the queue. This must be
* a fast-pathed signal or we must have been
* out of queue space. So zero out the info.
*/
clear_siginfo(info);
info->si_signo = sig;
info->si_errno = 0;
info->si_code = SI_USER;
info->si_pid = 0;
info->si_uid = 0;
}
}
static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
signal: Only reschedule timers on signals timers have sent Thomas Gleixner wrote: > The CRIU support added a 'feature' which allows a user space task to send > arbitrary (kernel) signals to itself. The changelog says: > > The kernel prevents sending of siginfo with positive si_code, because > these codes are reserved for kernel. I think we can allow a task to > send such a siginfo to itself. This operation should not be dangerous. > > Quite contrary to that claim, it turns out that it is outright dangerous > for signals with info->si_code == SI_TIMER. The following code sequence in > a user space task allows to crash the kernel: > > id = timer_create(CLOCK_XXX, ..... signo = SIGX); > timer_set(id, ....); > info->si_signo = SIGX; > info->si_code = SI_TIMER: > info->_sifields._timer._tid = id; > info->_sifields._timer._sys_private = 2; > rt_[tg]sigqueueinfo(..., SIGX, info); > sigemptyset(&sigset); > sigaddset(&sigset, SIGX); > rt_sigtimedwait(sigset, info); > > For timers based on CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID this > results in a kernel crash because sigwait() dequeues the signal and the > dequeue code observes: > > info->si_code == SI_TIMER && info->_sifields._timer._sys_private != 0 > > which triggers the following callchain: > > do_schedule_next_timer() -> posix_cpu_timer_schedule() -> arm_timer() > > arm_timer() executes a list_add() on the timer, which is already armed via > the timer_set() syscall. That's a double list add which corrupts the posix > cpu timer list. As a consequence the kernel crashes on the next operation > touching the posix cpu timer list. > > Posix clocks which are internally implemented based on hrtimers are not > affected by this because hrtimer_start() can handle already armed timers > nicely, but it's a reliable way to trigger the WARN_ON() in > hrtimer_forward(), which complains about calling that function on an > already armed timer. This problem has existed since the posix timer code was merged into 2.5.63. A few releases earlier in 2.5.60 ptrace gained the ability to inject not just a signal (which linux has supported since 1.0) but the full siginfo of a signal. The core problem is that the code will reschedule in response to signals getting dequeued not just for signals the timers sent but for other signals that happen to a si_code of SI_TIMER. Avoid this confusion by testing to see if the queued signal was preallocated as all timer signals are preallocated, and so far only the timer code preallocates signals. Move the check for if a timer needs to be rescheduled up into collect_signal where the preallocation check must be performed, and pass the result back to dequeue_signal where the code reschedules timers. This makes it clear why the code cares about preallocated timers. Cc: stable@vger.kernel.org Reported-by: Thomas Gleixner <tglx@linutronix.de> History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reference: 66dd34ad31e5 ("signal: allow to send any siginfo to itself") Reference: 1669ce53e2ff ("Add PTRACE_GETSIGINFO and PTRACE_SETSIGINFO") Fixes: db8b50ba75f2 ("[PATCH] POSIX clocks & timers") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-06-13 09:31:16 +00:00
siginfo_t *info, bool *resched_timer)
{
int sig = next_signal(pending, mask);
if (sig)
signal: Only reschedule timers on signals timers have sent Thomas Gleixner wrote: > The CRIU support added a 'feature' which allows a user space task to send > arbitrary (kernel) signals to itself. The changelog says: > > The kernel prevents sending of siginfo with positive si_code, because > these codes are reserved for kernel. I think we can allow a task to > send such a siginfo to itself. This operation should not be dangerous. > > Quite contrary to that claim, it turns out that it is outright dangerous > for signals with info->si_code == SI_TIMER. The following code sequence in > a user space task allows to crash the kernel: > > id = timer_create(CLOCK_XXX, ..... signo = SIGX); > timer_set(id, ....); > info->si_signo = SIGX; > info->si_code = SI_TIMER: > info->_sifields._timer._tid = id; > info->_sifields._timer._sys_private = 2; > rt_[tg]sigqueueinfo(..., SIGX, info); > sigemptyset(&sigset); > sigaddset(&sigset, SIGX); > rt_sigtimedwait(sigset, info); > > For timers based on CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID this > results in a kernel crash because sigwait() dequeues the signal and the > dequeue code observes: > > info->si_code == SI_TIMER && info->_sifields._timer._sys_private != 0 > > which triggers the following callchain: > > do_schedule_next_timer() -> posix_cpu_timer_schedule() -> arm_timer() > > arm_timer() executes a list_add() on the timer, which is already armed via > the timer_set() syscall. That's a double list add which corrupts the posix > cpu timer list. As a consequence the kernel crashes on the next operation > touching the posix cpu timer list. > > Posix clocks which are internally implemented based on hrtimers are not > affected by this because hrtimer_start() can handle already armed timers > nicely, but it's a reliable way to trigger the WARN_ON() in > hrtimer_forward(), which complains about calling that function on an > already armed timer. This problem has existed since the posix timer code was merged into 2.5.63. A few releases earlier in 2.5.60 ptrace gained the ability to inject not just a signal (which linux has supported since 1.0) but the full siginfo of a signal. The core problem is that the code will reschedule in response to signals getting dequeued not just for signals the timers sent but for other signals that happen to a si_code of SI_TIMER. Avoid this confusion by testing to see if the queued signal was preallocated as all timer signals are preallocated, and so far only the timer code preallocates signals. Move the check for if a timer needs to be rescheduled up into collect_signal where the preallocation check must be performed, and pass the result back to dequeue_signal where the code reschedules timers. This makes it clear why the code cares about preallocated timers. Cc: stable@vger.kernel.org Reported-by: Thomas Gleixner <tglx@linutronix.de> History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reference: 66dd34ad31e5 ("signal: allow to send any siginfo to itself") Reference: 1669ce53e2ff ("Add PTRACE_GETSIGINFO and PTRACE_SETSIGINFO") Fixes: db8b50ba75f2 ("[PATCH] POSIX clocks & timers") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-06-13 09:31:16 +00:00
collect_signal(sig, pending, info, resched_timer);
return sig;
}
/*
* Dequeue a signal and return the element to the caller, which is
* expected to free it.
*
* All callers have to hold the siglock.
*/
int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
{
signal: Only reschedule timers on signals timers have sent Thomas Gleixner wrote: > The CRIU support added a 'feature' which allows a user space task to send > arbitrary (kernel) signals to itself. The changelog says: > > The kernel prevents sending of siginfo with positive si_code, because > these codes are reserved for kernel. I think we can allow a task to > send such a siginfo to itself. This operation should not be dangerous. > > Quite contrary to that claim, it turns out that it is outright dangerous > for signals with info->si_code == SI_TIMER. The following code sequence in > a user space task allows to crash the kernel: > > id = timer_create(CLOCK_XXX, ..... signo = SIGX); > timer_set(id, ....); > info->si_signo = SIGX; > info->si_code = SI_TIMER: > info->_sifields._timer._tid = id; > info->_sifields._timer._sys_private = 2; > rt_[tg]sigqueueinfo(..., SIGX, info); > sigemptyset(&sigset); > sigaddset(&sigset, SIGX); > rt_sigtimedwait(sigset, info); > > For timers based on CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID this > results in a kernel crash because sigwait() dequeues the signal and the > dequeue code observes: > > info->si_code == SI_TIMER && info->_sifields._timer._sys_private != 0 > > which triggers the following callchain: > > do_schedule_next_timer() -> posix_cpu_timer_schedule() -> arm_timer() > > arm_timer() executes a list_add() on the timer, which is already armed via > the timer_set() syscall. That's a double list add which corrupts the posix > cpu timer list. As a consequence the kernel crashes on the next operation > touching the posix cpu timer list. > > Posix clocks which are internally implemented based on hrtimers are not > affected by this because hrtimer_start() can handle already armed timers > nicely, but it's a reliable way to trigger the WARN_ON() in > hrtimer_forward(), which complains about calling that function on an > already armed timer. This problem has existed since the posix timer code was merged into 2.5.63. A few releases earlier in 2.5.60 ptrace gained the ability to inject not just a signal (which linux has supported since 1.0) but the full siginfo of a signal. The core problem is that the code will reschedule in response to signals getting dequeued not just for signals the timers sent but for other signals that happen to a si_code of SI_TIMER. Avoid this confusion by testing to see if the queued signal was preallocated as all timer signals are preallocated, and so far only the timer code preallocates signals. Move the check for if a timer needs to be rescheduled up into collect_signal where the preallocation check must be performed, and pass the result back to dequeue_signal where the code reschedules timers. This makes it clear why the code cares about preallocated timers. Cc: stable@vger.kernel.org Reported-by: Thomas Gleixner <tglx@linutronix.de> History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reference: 66dd34ad31e5 ("signal: allow to send any siginfo to itself") Reference: 1669ce53e2ff ("Add PTRACE_GETSIGINFO and PTRACE_SETSIGINFO") Fixes: db8b50ba75f2 ("[PATCH] POSIX clocks & timers") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-06-13 09:31:16 +00:00
bool resched_timer = false;
int signr;
/* We only dequeue private signals from ourselves, we don't let
* signalfd steal them
*/
signal: Only reschedule timers on signals timers have sent Thomas Gleixner wrote: > The CRIU support added a 'feature' which allows a user space task to send > arbitrary (kernel) signals to itself. The changelog says: > > The kernel prevents sending of siginfo with positive si_code, because > these codes are reserved for kernel. I think we can allow a task to > send such a siginfo to itself. This operation should not be dangerous. > > Quite contrary to that claim, it turns out that it is outright dangerous > for signals with info->si_code == SI_TIMER. The following code sequence in > a user space task allows to crash the kernel: > > id = timer_create(CLOCK_XXX, ..... signo = SIGX); > timer_set(id, ....); > info->si_signo = SIGX; > info->si_code = SI_TIMER: > info->_sifields._timer._tid = id; > info->_sifields._timer._sys_private = 2; > rt_[tg]sigqueueinfo(..., SIGX, info); > sigemptyset(&sigset); > sigaddset(&sigset, SIGX); > rt_sigtimedwait(sigset, info); > > For timers based on CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID this > results in a kernel crash because sigwait() dequeues the signal and the > dequeue code observes: > > info->si_code == SI_TIMER && info->_sifields._timer._sys_private != 0 > > which triggers the following callchain: > > do_schedule_next_timer() -> posix_cpu_timer_schedule() -> arm_timer() > > arm_timer() executes a list_add() on the timer, which is already armed via > the timer_set() syscall. That's a double list add which corrupts the posix > cpu timer list. As a consequence the kernel crashes on the next operation > touching the posix cpu timer list. > > Posix clocks which are internally implemented based on hrtimers are not > affected by this because hrtimer_start() can handle already armed timers > nicely, but it's a reliable way to trigger the WARN_ON() in > hrtimer_forward(), which complains about calling that function on an > already armed timer. This problem has existed since the posix timer code was merged into 2.5.63. A few releases earlier in 2.5.60 ptrace gained the ability to inject not just a signal (which linux has supported since 1.0) but the full siginfo of a signal. The core problem is that the code will reschedule in response to signals getting dequeued not just for signals the timers sent but for other signals that happen to a si_code of SI_TIMER. Avoid this confusion by testing to see if the queued signal was preallocated as all timer signals are preallocated, and so far only the timer code preallocates signals. Move the check for if a timer needs to be rescheduled up into collect_signal where the preallocation check must be performed, and pass the result back to dequeue_signal where the code reschedules timers. This makes it clear why the code cares about preallocated timers. Cc: stable@vger.kernel.org Reported-by: Thomas Gleixner <tglx@linutronix.de> History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reference: 66dd34ad31e5 ("signal: allow to send any siginfo to itself") Reference: 1669ce53e2ff ("Add PTRACE_GETSIGINFO and PTRACE_SETSIGINFO") Fixes: db8b50ba75f2 ("[PATCH] POSIX clocks & timers") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-06-13 09:31:16 +00:00
signr = __dequeue_signal(&tsk->pending, mask, info, &resched_timer);
if (!signr) {
signr = __dequeue_signal(&tsk->signal->shared_pending,
signal: Only reschedule timers on signals timers have sent Thomas Gleixner wrote: > The CRIU support added a 'feature' which allows a user space task to send > arbitrary (kernel) signals to itself. The changelog says: > > The kernel prevents sending of siginfo with positive si_code, because > these codes are reserved for kernel. I think we can allow a task to > send such a siginfo to itself. This operation should not be dangerous. > > Quite contrary to that claim, it turns out that it is outright dangerous > for signals with info->si_code == SI_TIMER. The following code sequence in > a user space task allows to crash the kernel: > > id = timer_create(CLOCK_XXX, ..... signo = SIGX); > timer_set(id, ....); > info->si_signo = SIGX; > info->si_code = SI_TIMER: > info->_sifields._timer._tid = id; > info->_sifields._timer._sys_private = 2; > rt_[tg]sigqueueinfo(..., SIGX, info); > sigemptyset(&sigset); > sigaddset(&sigset, SIGX); > rt_sigtimedwait(sigset, info); > > For timers based on CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID this > results in a kernel crash because sigwait() dequeues the signal and the > dequeue code observes: > > info->si_code == SI_TIMER && info->_sifields._timer._sys_private != 0 > > which triggers the following callchain: > > do_schedule_next_timer() -> posix_cpu_timer_schedule() -> arm_timer() > > arm_timer() executes a list_add() on the timer, which is already armed via > the timer_set() syscall. That's a double list add which corrupts the posix > cpu timer list. As a consequence the kernel crashes on the next operation > touching the posix cpu timer list. > > Posix clocks which are internally implemented based on hrtimers are not > affected by this because hrtimer_start() can handle already armed timers > nicely, but it's a reliable way to trigger the WARN_ON() in > hrtimer_forward(), which complains about calling that function on an > already armed timer. This problem has existed since the posix timer code was merged into 2.5.63. A few releases earlier in 2.5.60 ptrace gained the ability to inject not just a signal (which linux has supported since 1.0) but the full siginfo of a signal. The core problem is that the code will reschedule in response to signals getting dequeued not just for signals the timers sent but for other signals that happen to a si_code of SI_TIMER. Avoid this confusion by testing to see if the queued signal was preallocated as all timer signals are preallocated, and so far only the timer code preallocates signals. Move the check for if a timer needs to be rescheduled up into collect_signal where the preallocation check must be performed, and pass the result back to dequeue_signal where the code reschedules timers. This makes it clear why the code cares about preallocated timers. Cc: stable@vger.kernel.org Reported-by: Thomas Gleixner <tglx@linutronix.de> History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reference: 66dd34ad31e5 ("signal: allow to send any siginfo to itself") Reference: 1669ce53e2ff ("Add PTRACE_GETSIGINFO and PTRACE_SETSIGINFO") Fixes: db8b50ba75f2 ("[PATCH] POSIX clocks & timers") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-06-13 09:31:16 +00:00
mask, info, &resched_timer);
#ifdef CONFIG_POSIX_TIMERS
/*
* itimer signal ?
*
* itimers are process shared and we restart periodic
* itimers in the signal delivery path to prevent DoS
* attacks in the high resolution timer case. This is
* compliant with the old way of self-restarting
* itimers, as the SIGALRM is a legacy signal and only
* queued once. Changing the restart behaviour to
* restart the timer in the signal dequeue path is
* reducing the timer noise on heavy loaded !highres
* systems too.
*/
if (unlikely(signr == SIGALRM)) {
struct hrtimer *tmr = &tsk->signal->real_timer;
if (!hrtimer_is_queued(tmr) &&
tsk->signal->it_real_incr != 0) {
hrtimer_forward(tmr, tmr->base->get_time(),
tsk->signal->it_real_incr);
hrtimer_restart(tmr);
}
}
#endif
}
recalc_sigpending();
if (!signr)
return 0;
if (unlikely(sig_kernel_stop(signr))) {
/*
* Set a marker that we have dequeued a stop signal. Our
* caller might release the siglock and then the pending
* stop signal it is about to process is no longer in the
* pending bitmasks, but must still be cleared by a SIGCONT
* (and overruled by a SIGKILL). So those cases clear this
* shared flag after we've set it. Note that this flag may
* remain set after the signal we return is ignored or
* handled. That doesn't matter because its only purpose
* is to alert stop-signal processing code when another
* processor has come along and cleared the flag.
*/
current->jobctl |= JOBCTL_STOP_DEQUEUED;
}
#ifdef CONFIG_POSIX_TIMERS
signal: Only reschedule timers on signals timers have sent Thomas Gleixner wrote: > The CRIU support added a 'feature' which allows a user space task to send > arbitrary (kernel) signals to itself. The changelog says: > > The kernel prevents sending of siginfo with positive si_code, because > these codes are reserved for kernel. I think we can allow a task to > send such a siginfo to itself. This operation should not be dangerous. > > Quite contrary to that claim, it turns out that it is outright dangerous > for signals with info->si_code == SI_TIMER. The following code sequence in > a user space task allows to crash the kernel: > > id = timer_create(CLOCK_XXX, ..... signo = SIGX); > timer_set(id, ....); > info->si_signo = SIGX; > info->si_code = SI_TIMER: > info->_sifields._timer._tid = id; > info->_sifields._timer._sys_private = 2; > rt_[tg]sigqueueinfo(..., SIGX, info); > sigemptyset(&sigset); > sigaddset(&sigset, SIGX); > rt_sigtimedwait(sigset, info); > > For timers based on CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID this > results in a kernel crash because sigwait() dequeues the signal and the > dequeue code observes: > > info->si_code == SI_TIMER && info->_sifields._timer._sys_private != 0 > > which triggers the following callchain: > > do_schedule_next_timer() -> posix_cpu_timer_schedule() -> arm_timer() > > arm_timer() executes a list_add() on the timer, which is already armed via > the timer_set() syscall. That's a double list add which corrupts the posix > cpu timer list. As a consequence the kernel crashes on the next operation > touching the posix cpu timer list. > > Posix clocks which are internally implemented based on hrtimers are not > affected by this because hrtimer_start() can handle already armed timers > nicely, but it's a reliable way to trigger the WARN_ON() in > hrtimer_forward(), which complains about calling that function on an > already armed timer. This problem has existed since the posix timer code was merged into 2.5.63. A few releases earlier in 2.5.60 ptrace gained the ability to inject not just a signal (which linux has supported since 1.0) but the full siginfo of a signal. The core problem is that the code will reschedule in response to signals getting dequeued not just for signals the timers sent but for other signals that happen to a si_code of SI_TIMER. Avoid this confusion by testing to see if the queued signal was preallocated as all timer signals are preallocated, and so far only the timer code preallocates signals. Move the check for if a timer needs to be rescheduled up into collect_signal where the preallocation check must be performed, and pass the result back to dequeue_signal where the code reschedules timers. This makes it clear why the code cares about preallocated timers. Cc: stable@vger.kernel.org Reported-by: Thomas Gleixner <tglx@linutronix.de> History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reference: 66dd34ad31e5 ("signal: allow to send any siginfo to itself") Reference: 1669ce53e2ff ("Add PTRACE_GETSIGINFO and PTRACE_SETSIGINFO") Fixes: db8b50ba75f2 ("[PATCH] POSIX clocks & timers") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-06-13 09:31:16 +00:00
if (resched_timer) {
/*
* Release the siglock to ensure proper locking order
* of timer locks outside of siglocks. Note, we leave
* irqs disabled here, since the posix-timers code is
* about to disable them again anyway.
*/
spin_unlock(&tsk->sighand->siglock);
posixtimer_rearm(info);
spin_lock(&tsk->sighand->siglock);
/* Don't expose the si_sys_private value to userspace */
info->si_sys_private = 0;
}
#endif
return signr;
}
/*
* Tell a process that it has a new active signal..
*
* NOTE! we rely on the previous spin_lock to
* lock interrupts for us! We can only be called with
* "siglock" held, and the local interrupt must
* have been disabled when that got acquired!
*
* No need to set need_resched since signal event passing
* goes through ->blocked
*/
void signal_wake_up_state(struct task_struct *t, unsigned int state)
{
set_tsk_thread_flag(t, TIF_SIGPENDING);
/*
* TASK_WAKEKILL also means wake it up in the stopped/traced/killable
* case. We don't check t->state here because there is a race with it
* executing another processor and just now entering stopped state.
* By using wake_up_state, we ensure the process will wake up and
* handle its death signal.
*/
if (!wake_up_state(t, state | TASK_INTERRUPTIBLE))
kick_process(t);
}
/*
* Remove signals in mask from the pending set and queue.
* Returns 1 if any signals were found.
*
* All callers must be holding the siglock.
*/
static int flush_sigqueue_mask(sigset_t *mask, struct sigpending *s)
{
struct sigqueue *q, *n;
sigset_t m;
sigandsets(&m, mask, &s->signal);
if (sigisemptyset(&m))
return 0;
sigandnsets(&s->signal, &s->signal, mask);
list_for_each_entry_safe(q, n, &s->list, list) {
if (sigismember(mask, q->info.si_signo)) {
list_del_init(&q->list);
__sigqueue_free(q);
}
}
return 1;
}
static inline int is_si_special(const struct siginfo *info)
{
return info <= SEND_SIG_FORCED;
}
static inline bool si_fromuser(const struct siginfo *info)
{
return info == SEND_SIG_NOINFO ||
(!is_si_special(info) && SI_FROMUSER(info));
}
/*
* called with RCU read lock from check_kill_permission()
*/
static int kill_ok_by_cred(struct task_struct *t)
{
const struct cred *cred = current_cred();
const struct cred *tcred = __task_cred(t);
if (uid_eq(cred->euid, tcred->suid) ||
uid_eq(cred->euid, tcred->uid) ||
uid_eq(cred->uid, tcred->suid) ||
uid_eq(cred->uid, tcred->uid))
return 1;
if (ns_capable(tcred->user_ns, CAP_KILL))
return 1;
return 0;
}
/*
* Bad permissions for sending the signal
* - the caller must hold the RCU read lock
*/
static int check_kill_permission(int sig, struct siginfo *info,
struct task_struct *t)
{
struct pid *sid;
int error;
if (!valid_signal(sig))
return -EINVAL;
if (!si_fromuser(info))
return 0;
error = audit_signal_info(sig, t); /* Let audit system see the signal */
if (error)
return error;
signals: check_kill_permission(): don't check creds if same_thread_group() Andrew Tridgell reports that aio_read(SIGEV_SIGNAL) can fail if the notification from the helper thread races with setresuid(), see http://samba.org/~tridge/junkcode/aio_uid.c This happens because check_kill_permission() doesn't permit sending a signal to the task with the different cred->xids. But there is not any security reason to check ->cred's when the task sends a signal (private or group-wide) to its sub-thread. Whatever we do, any thread can bypass all security checks and send SIGKILL to all threads, or it can block a signal SIG and do kill(gettid(), SIG) to deliver this signal to another sub-thread. Not to mention that CLONE_THREAD implies CLONE_VM. Change check_kill_permission() to avoid the credentials check when the sender and the target are from the same thread group. Also, move "cred = current_cred()" down to avoid calling get_current() twice. Note: David Howells pointed out we could relax this even more, the CLONE_SIGHAND (without CLONE_THREAD) case probably does not need these checks too. Roland said: : The glibc (libpthread) that does set*id across threads has : been in use for a while (2.3.4?), probably in distro's using kernels as old : or older than any active -stable streams. In the race in question, this : kernel bug is breaking valid POSIX application expectations. Reported-by: Andrew Tridgell <tridge@samba.org> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Roland McGrath <roland@redhat.com> Acked-by: David Howells <dhowells@redhat.com> Cc: Eric Paris <eparis@parisplace.org> Cc: Jakub Jelinek <jakub@redhat.com> Cc: James Morris <jmorris@namei.org> Cc: Roland McGrath <roland@redhat.com> Cc: Stephen Smalley <sds@tycho.nsa.gov> Cc: <stable@kernel.org> [all kernel versions] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-05-26 21:42:54 +00:00
if (!same_thread_group(current, t) &&
!kill_ok_by_cred(t)) {
switch (sig) {
case SIGCONT:
sid = task_session(t);
/*
* We don't return the error if sid == NULL. The
* task was unhashed, the caller must notice this.
*/
if (!sid || sid == task_session(current))
break;
default:
return -EPERM;
}
}
return security_task_kill(t, info, sig, NULL);
}
ptrace: implement TRAP_NOTIFY and use it for group stop events Currently there's no way for ptracer to find out whether group stop finished other than polling with INTERRUPT - GETSIGINFO - CONT sequence. This patch implements group stop notification for ptracer using STOP traps. When group stop state of a seized tracee changes, JOBCTL_TRAP_NOTIFY is set, which schedules a STOP trap which is sticky - it isn't cleared by other traps and at least one STOP trap will happen eventually. STOP trap is synchronization point for event notification and the tracer can determine the current group stop state by looking at the signal number portion of exit code (si_status from waitid(2) or si_code from PTRACE_GETSIGINFO). Notifications are generated both on start and end of group stops but, because group stop participation always happens before STOP trap, this doesn't cause an extra trap while tracee is participating in group stop. The symmetry will be useful later. Note that this notification works iff tracee is not trapped. Currently there is no way to be notified of group stop state changes while tracee is trapped. This will be addressed by a later patch. An example program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) pause(); tracer = fork(); if (!tracer) { siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); repeat: waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (!si.si_code) { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); goto repeat; } printf("tracer: stopped=%d signo=%d\n", si.si_signo != SIGTRAP, si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, NULL); goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } In the above program, tracer keeps tracee running and gets notification of each group stop state changes. # ./test-notify tracer: stopped=0 signo=5 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:17 +00:00
/**
* ptrace_trap_notify - schedule trap to notify ptracer
* @t: tracee wanting to notify tracer
*
* This function schedules sticky ptrace trap which is cleared on the next
* TRAP_STOP to notify ptracer of an event. @t must have been seized by
* ptracer.
*
ptrace: implement PTRACE_LISTEN The previous patch implemented async notification for ptrace but it only worked while trace is running. This patch introduces PTRACE_LISTEN which is suggested by Oleg Nestrov. It's allowed iff tracee is in STOP trap and puts tracee into quasi-running state - tracee never really runs but wait(2) and ptrace(2) consider it to be running. While ptracer is listening, tracee is allowed to re-enter STOP to notify an async event. Listening state is cleared on the first notification. Ptracer can also clear it by issuing INTERRUPT - tracee will re-trap into STOP with listening state cleared. This allows ptracer to monitor group stop state without running tracee - use INTERRUPT to put tracee into STOP trap, issue LISTEN and then wait(2) to wait for the next group stop event. When it happens, PTRACE_GETSIGINFO provides information to determine the current state. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_LISTEN 0x4208 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) pause(); tracer = fork(); if (!tracer) { siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); repeat: waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (!si.si_code) { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); goto repeat; } printf("tracer: stopped=%d signo=%d\n", si.si_signo != SIGTRAP, si.si_signo); if (si.si_signo != SIGTRAP) ptrace(PTRACE_LISTEN, tracee, NULL, NULL); else ptrace(PTRACE_CONT, tracee, NULL, NULL); goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } This is identical to the program to test TRAP_NOTIFY except that tracee is PTRACE_LISTEN'd instead of PTRACE_CONT'd when group stopped. This allows ptracer to monitor when group stop ends without running tracee. # ./test-listen tracer: stopped=0 signo=5 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 -v2: Moved JOBCTL_LISTENING check in wait_task_stopped() into task_stopped_code() as suggested by Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:18 +00:00
* If @t is running, STOP trap will be taken. If trapped for STOP and
* ptracer is listening for events, tracee is woken up so that it can
* re-trap for the new event. If trapped otherwise, STOP trap will be
* eventually taken without returning to userland after the existing traps
* are finished by PTRACE_CONT.
ptrace: implement TRAP_NOTIFY and use it for group stop events Currently there's no way for ptracer to find out whether group stop finished other than polling with INTERRUPT - GETSIGINFO - CONT sequence. This patch implements group stop notification for ptracer using STOP traps. When group stop state of a seized tracee changes, JOBCTL_TRAP_NOTIFY is set, which schedules a STOP trap which is sticky - it isn't cleared by other traps and at least one STOP trap will happen eventually. STOP trap is synchronization point for event notification and the tracer can determine the current group stop state by looking at the signal number portion of exit code (si_status from waitid(2) or si_code from PTRACE_GETSIGINFO). Notifications are generated both on start and end of group stops but, because group stop participation always happens before STOP trap, this doesn't cause an extra trap while tracee is participating in group stop. The symmetry will be useful later. Note that this notification works iff tracee is not trapped. Currently there is no way to be notified of group stop state changes while tracee is trapped. This will be addressed by a later patch. An example program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) pause(); tracer = fork(); if (!tracer) { siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); repeat: waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (!si.si_code) { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); goto repeat; } printf("tracer: stopped=%d signo=%d\n", si.si_signo != SIGTRAP, si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, NULL); goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } In the above program, tracer keeps tracee running and gets notification of each group stop state changes. # ./test-notify tracer: stopped=0 signo=5 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:17 +00:00
*
* CONTEXT:
* Must be called with @task->sighand->siglock held.
*/
static void ptrace_trap_notify(struct task_struct *t)
{
WARN_ON_ONCE(!(t->ptrace & PT_SEIZED));
assert_spin_locked(&t->sighand->siglock);
task_set_jobctl_pending(t, JOBCTL_TRAP_NOTIFY);
ptrace_signal_wake_up(t, t->jobctl & JOBCTL_LISTENING);
ptrace: implement TRAP_NOTIFY and use it for group stop events Currently there's no way for ptracer to find out whether group stop finished other than polling with INTERRUPT - GETSIGINFO - CONT sequence. This patch implements group stop notification for ptracer using STOP traps. When group stop state of a seized tracee changes, JOBCTL_TRAP_NOTIFY is set, which schedules a STOP trap which is sticky - it isn't cleared by other traps and at least one STOP trap will happen eventually. STOP trap is synchronization point for event notification and the tracer can determine the current group stop state by looking at the signal number portion of exit code (si_status from waitid(2) or si_code from PTRACE_GETSIGINFO). Notifications are generated both on start and end of group stops but, because group stop participation always happens before STOP trap, this doesn't cause an extra trap while tracee is participating in group stop. The symmetry will be useful later. Note that this notification works iff tracee is not trapped. Currently there is no way to be notified of group stop state changes while tracee is trapped. This will be addressed by a later patch. An example program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) pause(); tracer = fork(); if (!tracer) { siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); repeat: waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (!si.si_code) { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); goto repeat; } printf("tracer: stopped=%d signo=%d\n", si.si_signo != SIGTRAP, si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, NULL); goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } In the above program, tracer keeps tracee running and gets notification of each group stop state changes. # ./test-notify tracer: stopped=0 signo=5 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:17 +00:00
}
/*
* Handle magic process-wide effects of stop/continue signals. Unlike
* the signal actions, these happen immediately at signal-generation
* time regardless of blocking, ignoring, or handling. This does the
* actual continuing for SIGCONT, but not the actual stopping for stop
* signals. The process stop is done as a signal action for SIG_DFL.
*
* Returns true if the signal should be actually delivered, otherwise
* it should be dropped.
*/
coredump: only SIGKILL should interrupt the coredumping task There are 2 well known and ancient problems with coredump/signals, and a lot of related bug reports: - do_coredump() clears TIF_SIGPENDING but of course this can't help if, say, SIGCHLD comes after that. In this case the coredump can fail unexpectedly. See for example wait_for_dump_helper()->signal_pending() check but there are other reasons. - At the same time, dumping a huge core on the slow media can take a lot of time/resources and there is no way to kill the coredumping task reliably. In particular this is not oom_kill-friendly. This patch tries to fix the 1st problem, and makes the preparation for the next changes. We add the new SIGNAL_GROUP_COREDUMP flag set by zap_threads() to indicate that this process dumps the core. prepare_signal() checks this flag and nacks any signal except SIGKILL. Note that this check tries to be conservative, in the long term we should probably treat the SIGNAL_GROUP_EXIT case equally but this needs more discussion. See marc.info/?l=linux-kernel&m=120508897917439 Notes: - recalc_sigpending() doesn't check SIGNAL_GROUP_COREDUMP. The patch assumes that dump_write/etc paths should never call it, but we can change it as well. - There is another source of TIF_SIGPENDING, freezer. This will be addressed separately. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Tested-by: Mandeep Singh Baines <msb@chromium.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Neil Horman <nhorman@redhat.com> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-30 22:28:10 +00:00
static bool prepare_signal(int sig, struct task_struct *p, bool force)
{
struct signal_struct *signal = p->signal;
struct task_struct *t;
sigset_t flush;
coredump: only SIGKILL should interrupt the coredumping task There are 2 well known and ancient problems with coredump/signals, and a lot of related bug reports: - do_coredump() clears TIF_SIGPENDING but of course this can't help if, say, SIGCHLD comes after that. In this case the coredump can fail unexpectedly. See for example wait_for_dump_helper()->signal_pending() check but there are other reasons. - At the same time, dumping a huge core on the slow media can take a lot of time/resources and there is no way to kill the coredumping task reliably. In particular this is not oom_kill-friendly. This patch tries to fix the 1st problem, and makes the preparation for the next changes. We add the new SIGNAL_GROUP_COREDUMP flag set by zap_threads() to indicate that this process dumps the core. prepare_signal() checks this flag and nacks any signal except SIGKILL. Note that this check tries to be conservative, in the long term we should probably treat the SIGNAL_GROUP_EXIT case equally but this needs more discussion. See marc.info/?l=linux-kernel&m=120508897917439 Notes: - recalc_sigpending() doesn't check SIGNAL_GROUP_COREDUMP. The patch assumes that dump_write/etc paths should never call it, but we can change it as well. - There is another source of TIF_SIGPENDING, freezer. This will be addressed separately. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Tested-by: Mandeep Singh Baines <msb@chromium.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Neil Horman <nhorman@redhat.com> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-30 22:28:10 +00:00
if (signal->flags & (SIGNAL_GROUP_EXIT | SIGNAL_GROUP_COREDUMP)) {
if (!(signal->flags & SIGNAL_GROUP_EXIT))
coredump: only SIGKILL should interrupt the coredumping task There are 2 well known and ancient problems with coredump/signals, and a lot of related bug reports: - do_coredump() clears TIF_SIGPENDING but of course this can't help if, say, SIGCHLD comes after that. In this case the coredump can fail unexpectedly. See for example wait_for_dump_helper()->signal_pending() check but there are other reasons. - At the same time, dumping a huge core on the slow media can take a lot of time/resources and there is no way to kill the coredumping task reliably. In particular this is not oom_kill-friendly. This patch tries to fix the 1st problem, and makes the preparation for the next changes. We add the new SIGNAL_GROUP_COREDUMP flag set by zap_threads() to indicate that this process dumps the core. prepare_signal() checks this flag and nacks any signal except SIGKILL. Note that this check tries to be conservative, in the long term we should probably treat the SIGNAL_GROUP_EXIT case equally but this needs more discussion. See marc.info/?l=linux-kernel&m=120508897917439 Notes: - recalc_sigpending() doesn't check SIGNAL_GROUP_COREDUMP. The patch assumes that dump_write/etc paths should never call it, but we can change it as well. - There is another source of TIF_SIGPENDING, freezer. This will be addressed separately. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Tested-by: Mandeep Singh Baines <msb@chromium.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Neil Horman <nhorman@redhat.com> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-30 22:28:10 +00:00
return sig == SIGKILL;
/*
* The process is in the middle of dying, nothing to do.
*/
} else if (sig_kernel_stop(sig)) {
/*
* This is a stop signal. Remove SIGCONT from all queues.
*/
siginitset(&flush, sigmask(SIGCONT));
flush_sigqueue_mask(&flush, &signal->shared_pending);
for_each_thread(p, t)
flush_sigqueue_mask(&flush, &t->pending);
} else if (sig == SIGCONT) {
unsigned int why;
/*
* Remove all stop signals from all queues, wake all threads.
*/
siginitset(&flush, SIG_KERNEL_STOP_MASK);
flush_sigqueue_mask(&flush, &signal->shared_pending);
for_each_thread(p, t) {
flush_sigqueue_mask(&flush, &t->pending);
task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING);
ptrace: implement TRAP_NOTIFY and use it for group stop events Currently there's no way for ptracer to find out whether group stop finished other than polling with INTERRUPT - GETSIGINFO - CONT sequence. This patch implements group stop notification for ptracer using STOP traps. When group stop state of a seized tracee changes, JOBCTL_TRAP_NOTIFY is set, which schedules a STOP trap which is sticky - it isn't cleared by other traps and at least one STOP trap will happen eventually. STOP trap is synchronization point for event notification and the tracer can determine the current group stop state by looking at the signal number portion of exit code (si_status from waitid(2) or si_code from PTRACE_GETSIGINFO). Notifications are generated both on start and end of group stops but, because group stop participation always happens before STOP trap, this doesn't cause an extra trap while tracee is participating in group stop. The symmetry will be useful later. Note that this notification works iff tracee is not trapped. Currently there is no way to be notified of group stop state changes while tracee is trapped. This will be addressed by a later patch. An example program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) pause(); tracer = fork(); if (!tracer) { siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); repeat: waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (!si.si_code) { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); goto repeat; } printf("tracer: stopped=%d signo=%d\n", si.si_signo != SIGTRAP, si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, NULL); goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } In the above program, tracer keeps tracee running and gets notification of each group stop state changes. # ./test-notify tracer: stopped=0 signo=5 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:17 +00:00
if (likely(!(t->ptrace & PT_SEIZED)))
wake_up_state(t, __TASK_STOPPED);
else
ptrace_trap_notify(t);
}
/*
* Notify the parent with CLD_CONTINUED if we were stopped.
*
* If we were in the middle of a group stop, we pretend it
* was already finished, and then continued. Since SIGCHLD
* doesn't queue we report only CLD_STOPPED, as if the next
* CLD_CONTINUED was dropped.
*/
why = 0;
if (signal->flags & SIGNAL_STOP_STOPPED)
why |= SIGNAL_CLD_CONTINUED;
else if (signal->group_stop_count)
why |= SIGNAL_CLD_STOPPED;
if (why) {
/*
* The first thread which returns from do_signal_stop()
* will take ->siglock, notice SIGNAL_CLD_MASK, and
* notify its parent. See get_signal_to_deliver().
*/
signal_set_stop_flags(signal, why | SIGNAL_STOP_CONTINUED);
signal->group_stop_count = 0;
signal->group_exit_code = 0;
}
}
return !sig_ignored(p, sig, force);
}
/*
* Test if P wants to take SIG. After we've checked all threads with this,
* it's equivalent to finding no threads not blocking SIG. Any threads not
* blocking SIG were ruled out because they are not running and already
* have pending signals. Such threads will dequeue from the shared queue
* as soon as they're available, so putting the signal on the shared queue
* will be equivalent to sending it to one such thread.
*/
static inline int wants_signal(int sig, struct task_struct *p)
{
if (sigismember(&p->blocked, sig))
return 0;
if (p->flags & PF_EXITING)
return 0;
if (sig == SIGKILL)
return 1;
if (task_is_stopped_or_traced(p))
return 0;
return task_curr(p) || !signal_pending(p);
}
static void complete_signal(int sig, struct task_struct *p, int group)
{
struct signal_struct *signal = p->signal;
struct task_struct *t;
/*
* Now find a thread we can wake up to take the signal off the queue.
*
* If the main thread wants the signal, it gets first crack.
* Probably the least surprising to the average bear.
*/
if (wants_signal(sig, p))
t = p;
else if (!group || thread_group_empty(p))
/*
* There is just one thread and it does not need to be woken.
* It will dequeue unblocked signals before it runs again.
*/
return;
else {
/*
* Otherwise try to find a suitable thread.
*/
t = signal->curr_target;
while (!wants_signal(sig, t)) {
t = next_thread(t);
if (t == signal->curr_target)
/*
* No thread needs to be woken.
* Any eligible threads will see
* the signal in the queue soon.
*/
return;
}
signal->curr_target = t;
}
/*
* Found a killable thread. If the signal will be fatal,
* then start taking the whole group down immediately.
*/
if (sig_fatal(p, sig) &&
kernel/signal.c: remove the no longer needed SIGNAL_UNKILLABLE check in complete_signal() complete_signal() checks SIGNAL_UNKILLABLE before it starts to destroy the thread group, today this is wrong in many ways. If nothing else, fatal_signal_pending() should always imply that the whole thread group (except ->group_exit_task if it is not NULL) is killed, this check breaks the rule. After the previous changes we can rely on sig_task_ignored(); sig_fatal(sig) && SIGNAL_UNKILLABLE can only be true if we actually want to kill this task and sig == SIGKILL OR it is traced and debugger can intercept the signal. This should hopefully fix the problem reported by Dmitry. This test-case static int init(void *arg) { for (;;) pause(); } int main(void) { char stack[16 * 1024]; for (;;) { int pid = clone(init, stack + sizeof(stack)/2, CLONE_NEWPID | SIGCHLD, NULL); assert(pid > 0); assert(ptrace(PTRACE_ATTACH, pid, 0, 0) == 0); assert(waitpid(-1, NULL, WSTOPPED) == pid); assert(ptrace(PTRACE_DETACH, pid, 0, SIGSTOP) == 0); assert(syscall(__NR_tkill, pid, SIGKILL) == 0); assert(pid == wait(NULL)); } } triggers the WARN_ON_ONCE(!(task->jobctl & JOBCTL_STOP_PENDING)) in task_participate_group_stop(). do_signal_stop()->signal_group_exit() checks SIGNAL_GROUP_EXIT and return false, but task_set_jobctl_pending() checks fatal_signal_pending() and does not set JOBCTL_STOP_PENDING. And his should fix the minor security problem reported by Kyle, SECCOMP_RET_TRACE can miss fatal_signal_pending() the same way if the task is the root of a pid namespace. Link: http://lkml.kernel.org/r/20171103184246.GD21036@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Reported-by: Kyle Huey <me@kylehuey.com> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Kyle Huey <me@kylehuey.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-17 23:30:08 +00:00
!(signal->flags & SIGNAL_GROUP_EXIT) &&
!sigismember(&t->real_blocked, sig) &&
kernel/signal.c: remove the no longer needed SIGNAL_UNKILLABLE check in complete_signal() complete_signal() checks SIGNAL_UNKILLABLE before it starts to destroy the thread group, today this is wrong in many ways. If nothing else, fatal_signal_pending() should always imply that the whole thread group (except ->group_exit_task if it is not NULL) is killed, this check breaks the rule. After the previous changes we can rely on sig_task_ignored(); sig_fatal(sig) && SIGNAL_UNKILLABLE can only be true if we actually want to kill this task and sig == SIGKILL OR it is traced and debugger can intercept the signal. This should hopefully fix the problem reported by Dmitry. This test-case static int init(void *arg) { for (;;) pause(); } int main(void) { char stack[16 * 1024]; for (;;) { int pid = clone(init, stack + sizeof(stack)/2, CLONE_NEWPID | SIGCHLD, NULL); assert(pid > 0); assert(ptrace(PTRACE_ATTACH, pid, 0, 0) == 0); assert(waitpid(-1, NULL, WSTOPPED) == pid); assert(ptrace(PTRACE_DETACH, pid, 0, SIGSTOP) == 0); assert(syscall(__NR_tkill, pid, SIGKILL) == 0); assert(pid == wait(NULL)); } } triggers the WARN_ON_ONCE(!(task->jobctl & JOBCTL_STOP_PENDING)) in task_participate_group_stop(). do_signal_stop()->signal_group_exit() checks SIGNAL_GROUP_EXIT and return false, but task_set_jobctl_pending() checks fatal_signal_pending() and does not set JOBCTL_STOP_PENDING. And his should fix the minor security problem reported by Kyle, SECCOMP_RET_TRACE can miss fatal_signal_pending() the same way if the task is the root of a pid namespace. Link: http://lkml.kernel.org/r/20171103184246.GD21036@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Reported-by: Kyle Huey <me@kylehuey.com> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Kyle Huey <me@kylehuey.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-17 23:30:08 +00:00
(sig == SIGKILL || !p->ptrace)) {
/*
* This signal will be fatal to the whole group.
*/
if (!sig_kernel_coredump(sig)) {
/*
* Start a group exit and wake everybody up.
* This way we don't have other threads
* running and doing things after a slower
* thread has the fatal signal pending.
*/
signal->flags = SIGNAL_GROUP_EXIT;
signal->group_exit_code = sig;
signal->group_stop_count = 0;
t = p;
do {
task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);
} while_each_thread(p, t);
return;
}
}
/*
* The signal is already in the shared-pending queue.
* Tell the chosen thread to wake up and dequeue it.
*/
signal_wake_up(t, sig == SIGKILL);
return;
}
static inline int legacy_queue(struct sigpending *signals, int sig)
{
return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
}
user namespace: make signal.c respect user namespaces ipc/mqueue.c: for __SI_MESQ, convert the uid being sent to recipient's user namespace. (new, thanks Oleg) __send_signal: convert current's uid to the recipient's user namespace for any siginfo which is not SI_FROMKERNEL (patch from Oleg, thanks again :) do_notify_parent and do_notify_parent_cldstop: map task's uid to parent's user namespace ptrace_signal maps parent's uid into current's user namespace before including in signal to current. IIUC Oleg has argued that this shouldn't matter as the debugger will play with it, but it seems like not converting the value currently being set is misleading. Changelog: Sep 20: Inspired by Oleg's suggestion, define map_cred_ns() helper to simplify callers and help make clear what we are translating (which uid into which namespace). Passing the target task would make callers even easier to read, but we pass in user_ns because current_user_ns() != task_cred_xxx(current, user_ns). Sep 20: As recommended by Oleg, also put task_pid_vnr() under rcu_read_lock in ptrace_signal(). Sep 23: In send_signal(), detect when (user) signal is coming from an ancestor or unrelated user namespace. Pass that on to __send_signal, which sets si_uid to 0 or overflowuid if needed. Oct 12: Base on Oleg's fixup_uid() patch. On top of that, handle all SI_FROMKERNEL cases at callers, because we can't assume sender is current in those cases. Nov 10: (mhelsley) rename fixup_uid to more meaningful usern_fixup_signal_uid Nov 10: (akpm) make the !CONFIG_USER_NS case clearer Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Serge Hallyn <serge.hallyn@canonical.com> Subject: __send_signal: pass q->info, not info, to userns_fixup_signal_uid (v2) Eric Biederman pointed out that passing info is a bug and could lead to a NULL pointer deref to boot. A collection of signal, securebits, filecaps, cap_bounds, and a few other ltp tests passed with this kernel. Changelog: Nov 18: previous patch missed a leading '&' Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Dan Carpenter <dan.carpenter@oracle.com> Subject: ipc/mqueue: lock() => unlock() typo There was a double lock typo introduced in b085f4bd6b21 "user namespace: make signal.c respect user namespaces" Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Serge Hallyn <serge@hallyn.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-10 23:11:37 +00:00
#ifdef CONFIG_USER_NS
static inline void userns_fixup_signal_uid(struct siginfo *info, struct task_struct *t)
{
if (current_user_ns() == task_cred_xxx(t, user_ns))
return;
if (SI_FROMKERNEL(info))
return;
rcu_read_lock();
info->si_uid = from_kuid_munged(task_cred_xxx(t, user_ns),
make_kuid(current_user_ns(), info->si_uid));
rcu_read_unlock();
user namespace: make signal.c respect user namespaces ipc/mqueue.c: for __SI_MESQ, convert the uid being sent to recipient's user namespace. (new, thanks Oleg) __send_signal: convert current's uid to the recipient's user namespace for any siginfo which is not SI_FROMKERNEL (patch from Oleg, thanks again :) do_notify_parent and do_notify_parent_cldstop: map task's uid to parent's user namespace ptrace_signal maps parent's uid into current's user namespace before including in signal to current. IIUC Oleg has argued that this shouldn't matter as the debugger will play with it, but it seems like not converting the value currently being set is misleading. Changelog: Sep 20: Inspired by Oleg's suggestion, define map_cred_ns() helper to simplify callers and help make clear what we are translating (which uid into which namespace). Passing the target task would make callers even easier to read, but we pass in user_ns because current_user_ns() != task_cred_xxx(current, user_ns). Sep 20: As recommended by Oleg, also put task_pid_vnr() under rcu_read_lock in ptrace_signal(). Sep 23: In send_signal(), detect when (user) signal is coming from an ancestor or unrelated user namespace. Pass that on to __send_signal, which sets si_uid to 0 or overflowuid if needed. Oct 12: Base on Oleg's fixup_uid() patch. On top of that, handle all SI_FROMKERNEL cases at callers, because we can't assume sender is current in those cases. Nov 10: (mhelsley) rename fixup_uid to more meaningful usern_fixup_signal_uid Nov 10: (akpm) make the !CONFIG_USER_NS case clearer Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Serge Hallyn <serge.hallyn@canonical.com> Subject: __send_signal: pass q->info, not info, to userns_fixup_signal_uid (v2) Eric Biederman pointed out that passing info is a bug and could lead to a NULL pointer deref to boot. A collection of signal, securebits, filecaps, cap_bounds, and a few other ltp tests passed with this kernel. Changelog: Nov 18: previous patch missed a leading '&' Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Dan Carpenter <dan.carpenter@oracle.com> Subject: ipc/mqueue: lock() => unlock() typo There was a double lock typo introduced in b085f4bd6b21 "user namespace: make signal.c respect user namespaces" Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Serge Hallyn <serge@hallyn.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-10 23:11:37 +00:00
}
#else
static inline void userns_fixup_signal_uid(struct siginfo *info, struct task_struct *t)
{
return;
}
#endif
static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
int group, int from_ancestor_ns)
{
struct sigpending *pending;
struct sigqueue *q;
int override_rlimit;
int ret = 0, result;
assert_spin_locked(&t->sighand->siglock);
result = TRACE_SIGNAL_IGNORED;
if (!prepare_signal(sig, t,
from_ancestor_ns || (info == SEND_SIG_FORCED)))
goto ret;
pending = group ? &t->signal->shared_pending : &t->pending;
/*
* Short-circuit ignored signals and support queuing
* exactly one non-rt signal, so that we can get more
* detailed information about the cause of the signal.
*/
result = TRACE_SIGNAL_ALREADY_PENDING;
if (legacy_queue(pending, sig))
goto ret;
result = TRACE_SIGNAL_DELIVERED;
/*
* fast-pathed signals for kernel-internal things like SIGSTOP
* or SIGKILL.
*/
if (info == SEND_SIG_FORCED)
goto out_set;
/*
* Real-time signals must be queued if sent by sigqueue, or
* some other real-time mechanism. It is implementation
* defined whether kill() does so. We attempt to do so, on
* the principle of least surprise, but since kill is not
* allowed to fail with EAGAIN when low on memory we just
* make sure at least one signal gets delivered and don't
* pass on the info struct.
*/
if (sig < SIGRTMIN)
override_rlimit = (is_si_special(info) || info->si_code >= 0);
else
override_rlimit = 0;
q = __sigqueue_alloc(sig, t, GFP_ATOMIC, override_rlimit);
if (q) {
list_add_tail(&q->list, &pending->list);
switch ((unsigned long) info) {
case (unsigned long) SEND_SIG_NOINFO:
clear_siginfo(&q->info);
q->info.si_signo = sig;
q->info.si_errno = 0;
q->info.si_code = SI_USER;
q->info.si_pid = task_tgid_nr_ns(current,
task_active_pid_ns(t));
q->info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
break;
case (unsigned long) SEND_SIG_PRIV:
clear_siginfo(&q->info);
q->info.si_signo = sig;
q->info.si_errno = 0;
q->info.si_code = SI_KERNEL;
q->info.si_pid = 0;
q->info.si_uid = 0;
break;
default:
copy_siginfo(&q->info, info);
if (from_ancestor_ns)
q->info.si_pid = 0;
break;
}
user namespace: make signal.c respect user namespaces ipc/mqueue.c: for __SI_MESQ, convert the uid being sent to recipient's user namespace. (new, thanks Oleg) __send_signal: convert current's uid to the recipient's user namespace for any siginfo which is not SI_FROMKERNEL (patch from Oleg, thanks again :) do_notify_parent and do_notify_parent_cldstop: map task's uid to parent's user namespace ptrace_signal maps parent's uid into current's user namespace before including in signal to current. IIUC Oleg has argued that this shouldn't matter as the debugger will play with it, but it seems like not converting the value currently being set is misleading. Changelog: Sep 20: Inspired by Oleg's suggestion, define map_cred_ns() helper to simplify callers and help make clear what we are translating (which uid into which namespace). Passing the target task would make callers even easier to read, but we pass in user_ns because current_user_ns() != task_cred_xxx(current, user_ns). Sep 20: As recommended by Oleg, also put task_pid_vnr() under rcu_read_lock in ptrace_signal(). Sep 23: In send_signal(), detect when (user) signal is coming from an ancestor or unrelated user namespace. Pass that on to __send_signal, which sets si_uid to 0 or overflowuid if needed. Oct 12: Base on Oleg's fixup_uid() patch. On top of that, handle all SI_FROMKERNEL cases at callers, because we can't assume sender is current in those cases. Nov 10: (mhelsley) rename fixup_uid to more meaningful usern_fixup_signal_uid Nov 10: (akpm) make the !CONFIG_USER_NS case clearer Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Serge Hallyn <serge.hallyn@canonical.com> Subject: __send_signal: pass q->info, not info, to userns_fixup_signal_uid (v2) Eric Biederman pointed out that passing info is a bug and could lead to a NULL pointer deref to boot. A collection of signal, securebits, filecaps, cap_bounds, and a few other ltp tests passed with this kernel. Changelog: Nov 18: previous patch missed a leading '&' Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Dan Carpenter <dan.carpenter@oracle.com> Subject: ipc/mqueue: lock() => unlock() typo There was a double lock typo introduced in b085f4bd6b21 "user namespace: make signal.c respect user namespaces" Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Serge Hallyn <serge@hallyn.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-10 23:11:37 +00:00
userns_fixup_signal_uid(&q->info, t);
} else if (!is_si_special(info)) {
if (sig >= SIGRTMIN && info->si_code != SI_USER) {
/*
* Queue overflow, abort. We may abort if the
* signal was rt and sent by user using something
* other than kill().
*/
result = TRACE_SIGNAL_OVERFLOW_FAIL;
ret = -EAGAIN;
goto ret;
} else {
/*
* This is a silent loss of information. We still
* send the signal, but the *info bits are lost.
*/
result = TRACE_SIGNAL_LOSE_INFO;
}
}
out_set:
signalfd_notify(t, sig);
sigaddset(&pending->signal, sig);
complete_signal(sig, t, group);
ret:
trace_signal_generate(sig, info, t, group, result);
return ret;
}
static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
int group)
{
int from_ancestor_ns = 0;
#ifdef CONFIG_PID_NS
from_ancestor_ns = si_fromuser(info) &&
!task_pid_nr_ns(current, task_active_pid_ns(t));
#endif
return __send_signal(sig, info, t, group, from_ancestor_ns);
}
static void print_fatal_signal(int signr)
{
struct pt_regs *regs = signal_pt_regs();
pr_info("potentially unexpected fatal signal %d.\n", signr);
#if defined(__i386__) && !defined(__arch_um__)
pr_info("code at %08lx: ", regs->ip);
{
int i;
for (i = 0; i < 16; i++) {
unsigned char insn;
if (get_user(insn, (unsigned char *)(regs->ip + i)))
break;
pr_cont("%02x ", insn);
}
}
pr_cont("\n");
#endif
preempt_disable();
show_regs(regs);
preempt_enable();
}
static int __init setup_print_fatal_signals(char *str)
{
get_option (&str, &print_fatal_signals);
return 1;
}
__setup("print-fatal-signals=", setup_print_fatal_signals);
int
__group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
{
return send_signal(sig, info, p, 1);
}
static int
specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t)
{
return send_signal(sig, info, t, 0);
}
int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
bool group)
{
unsigned long flags;
int ret = -ESRCH;
if (lock_task_sighand(p, &flags)) {
ret = send_signal(sig, info, p, group);
unlock_task_sighand(p, &flags);
}
return ret;
}
/*
* Force a signal that the process can't ignore: if necessary
* we unblock the signal and change any SIG_IGN to SIG_DFL.
*
* Note: If we unblock the signal, we always reset it to SIG_DFL,
* since we do not want to have a signal handler that was blocked
* be invoked when user space had explicitly blocked it.
*
* We don't want to have recursive SIGSEGV's etc, for example,
* that is why we also clear SIGNAL_UNKILLABLE.
*/
int
force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
{
unsigned long int flags;
int ret, blocked, ignored;
struct k_sigaction *action;
spin_lock_irqsave(&t->sighand->siglock, flags);
action = &t->sighand->action[sig-1];
ignored = action->sa.sa_handler == SIG_IGN;
blocked = sigismember(&t->blocked, sig);
if (blocked || ignored) {
action->sa.sa_handler = SIG_DFL;
if (blocked) {
sigdelset(&t->blocked, sig);
recalc_sigpending_and_wake(t);
}
}
/*
* Don't clear SIGNAL_UNKILLABLE for traced tasks, users won't expect
* debugging to leave init killable.
*/
if (action->sa.sa_handler == SIG_DFL && !t->ptrace)
t->signal->flags &= ~SIGNAL_UNKILLABLE;
ret = specific_send_sig_info(sig, info, t);
spin_unlock_irqrestore(&t->sighand->siglock, flags);
return ret;
}
/*
* Nuke all other threads in the group.
*/
int zap_other_threads(struct task_struct *p)
{
struct task_struct *t = p;
int count = 0;
p->signal->group_stop_count = 0;
while_each_thread(p, t) {
task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
count++;
/* Don't bother with already dead threads */
if (t->exit_state)
continue;
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);
}
return count;
}
struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
unsigned long *flags)
{
struct sighand_struct *sighand;
rcu_read_lock();
for (;;) {
sighand = rcu_dereference(tsk->sighand);
if (unlikely(sighand == NULL))
break;
/*
* This sighand can be already freed and even reused, but
* we rely on SLAB_TYPESAFE_BY_RCU and sighand_ctor() which
* initializes ->siglock: this slab can't go away, it has
* the same object type, ->siglock can't be reinitialized.
*
* We need to ensure that tsk->sighand is still the same
* after we take the lock, we can race with de_thread() or
* __exit_signal(). In the latter case the next iteration
* must see ->sighand == NULL.
*/
spin_lock_irqsave(&sighand->siglock, *flags);
if (likely(sighand == tsk->sighand))
break;
spin_unlock_irqrestore(&sighand->siglock, *flags);
}
rcu_read_unlock();
return sighand;
}
/*
* send signal info to all the members of a group
*/
int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
{
int ret;
rcu_read_lock();
ret = check_kill_permission(sig, info, p);
rcu_read_unlock();
if (!ret && sig)
ret = do_send_sig_info(sig, info, p, true);
return ret;
}
/*
* __kill_pgrp_info() sends a signal to a process group: this is what the tty
* control characters do (^C, ^Z etc)
* - the caller must hold at least a readlock on tasklist_lock
*/
int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp)
{
struct task_struct *p = NULL;
int retval, success;
success = 0;
retval = -ESRCH;
do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
int err = group_send_sig_info(sig, info, p);
success |= !err;
retval = err;
} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
return success ? 0 : retval;
}
int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
{
int error = -ESRCH;
struct task_struct *p;
for (;;) {
rcu_read_lock();
p = pid_task(pid, PIDTYPE_PID);
if (p)
error = group_send_sig_info(sig, info, p);
rcu_read_unlock();
if (likely(!p || error != -ESRCH))
return error;
/*
* The task was unhashed in between, try again. If it
* is dead, pid_task() will return NULL, if we race with
* de_thread() it will find the new leader.
*/
}
}
static int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
{
int error;
rcu_read_lock();
error = kill_pid_info(sig, info, find_vpid(pid));
rcu_read_unlock();
return error;
}
static int kill_as_cred_perm(const struct cred *cred,
struct task_struct *target)
{
const struct cred *pcred = __task_cred(target);
if (!uid_eq(cred->euid, pcred->suid) && !uid_eq(cred->euid, pcred->uid) &&
!uid_eq(cred->uid, pcred->suid) && !uid_eq(cred->uid, pcred->uid))
return 0;
return 1;
}
/* like kill_pid_info(), but doesn't use uid/euid of "current" */
int kill_pid_info_as_cred(int sig, struct siginfo *info, struct pid *pid,
const struct cred *cred)
{
int ret = -EINVAL;
struct task_struct *p;
unsigned long flags;
if (!valid_signal(sig))
return ret;
rcu_read_lock();
p = pid_task(pid, PIDTYPE_PID);
if (!p) {
ret = -ESRCH;
goto out_unlock;
}
if (si_fromuser(info) && !kill_as_cred_perm(cred, p)) {
ret = -EPERM;
goto out_unlock;
}
ret = security_task_kill(p, info, sig, cred);
if (ret)
goto out_unlock;
if (sig) {
if (lock_task_sighand(p, &flags)) {
ret = __send_signal(sig, info, p, 1, 0);
unlock_task_sighand(p, &flags);
} else
ret = -ESRCH;
}
out_unlock:
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL_GPL(kill_pid_info_as_cred);
/*
* kill_something_info() interprets pid in interesting ways just like kill(2).
*
* POSIX specifies that kill(-1,sig) is unspecified, but what we have
* is probably wrong. Should make it like BSD or SYSV.
*/
static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
{
int ret;
if (pid > 0) {
rcu_read_lock();
ret = kill_pid_info(sig, info, find_vpid(pid));
rcu_read_unlock();
return ret;
}
/* -INT_MIN is undefined. Exclude this case to avoid a UBSAN warning */
if (pid == INT_MIN)
return -ESRCH;
read_lock(&tasklist_lock);
if (pid != -1) {
ret = __kill_pgrp_info(sig, info,
pid ? find_vpid(-pid) : task_pgrp(current));
} else {
int retval = 0, count = 0;
struct task_struct * p;
for_each_process(p) {
if (task_pid_vnr(p) > 1 &&
!same_thread_group(p, current)) {
int err = group_send_sig_info(sig, info, p);
++count;
if (err != -EPERM)
retval = err;
}
}
ret = count ? retval : -ESRCH;
}
read_unlock(&tasklist_lock);
return ret;
}
/*
* These are for backward compatibility with the rest of the kernel source.
*/
int send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
{
/*
* Make sure legacy kernel users don't send in bad values
* (normal paths check this in check_kill_permission).
*/
if (!valid_signal(sig))
return -EINVAL;
return do_send_sig_info(sig, info, p, false);
}
#define __si_special(priv) \
((priv) ? SEND_SIG_PRIV : SEND_SIG_NOINFO)
int
send_sig(int sig, struct task_struct *p, int priv)
{
return send_sig_info(sig, __si_special(priv), p);
}
void
force_sig(int sig, struct task_struct *p)
{
force_sig_info(sig, SEND_SIG_PRIV, p);
}
/*
* When things go south during signal handling, we
* will force a SIGSEGV. And if the signal that caused
* the problem was already a SIGSEGV, we'll want to
* make sure we don't even try to deliver the signal..
*/
int
force_sigsegv(int sig, struct task_struct *p)
{
if (sig == SIGSEGV) {
unsigned long flags;
spin_lock_irqsave(&p->sighand->siglock, flags);
p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
spin_unlock_irqrestore(&p->sighand->siglock, flags);
}
force_sig(SIGSEGV, p);
return 0;
}
int force_sig_fault(int sig, int code, void __user *addr
___ARCH_SI_TRAPNO(int trapno)
___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
, struct task_struct *t)
{
struct siginfo info;
clear_siginfo(&info);
info.si_signo = sig;
info.si_errno = 0;
info.si_code = code;
info.si_addr = addr;
#ifdef __ARCH_SI_TRAPNO
info.si_trapno = trapno;
#endif
#ifdef __ia64__
info.si_imm = imm;
info.si_flags = flags;
info.si_isr = isr;
#endif
return force_sig_info(info.si_signo, &info, t);
}
int send_sig_fault(int sig, int code, void __user *addr
___ARCH_SI_TRAPNO(int trapno)
___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
, struct task_struct *t)
{
struct siginfo info;
clear_siginfo(&info);
info.si_signo = sig;
info.si_errno = 0;
info.si_code = code;
info.si_addr = addr;
#ifdef __ARCH_SI_TRAPNO
info.si_trapno = trapno;
#endif
#ifdef __ia64__
info.si_imm = imm;
info.si_flags = flags;
info.si_isr = isr;
#endif
return send_sig_info(info.si_signo, &info, t);
}
int force_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *t)
{
struct siginfo info;
WARN_ON((code != BUS_MCEERR_AO) && (code != BUS_MCEERR_AR));
clear_siginfo(&info);
info.si_signo = SIGBUS;
info.si_errno = 0;
info.si_code = code;
info.si_addr = addr;
info.si_addr_lsb = lsb;
return force_sig_info(info.si_signo, &info, t);
}
int send_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *t)
{
struct siginfo info;
WARN_ON((code != BUS_MCEERR_AO) && (code != BUS_MCEERR_AR));
clear_siginfo(&info);
info.si_signo = SIGBUS;
info.si_errno = 0;
info.si_code = code;
info.si_addr = addr;
info.si_addr_lsb = lsb;
return send_sig_info(info.si_signo, &info, t);
}
EXPORT_SYMBOL(send_sig_mceerr);
int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper)
{
struct siginfo info;
clear_siginfo(&info);
info.si_signo = SIGSEGV;
info.si_errno = 0;
info.si_code = SEGV_BNDERR;
info.si_addr = addr;
info.si_lower = lower;
info.si_upper = upper;
return force_sig_info(info.si_signo, &info, current);
}
#ifdef SEGV_PKUERR
int force_sig_pkuerr(void __user *addr, u32 pkey)
{
struct siginfo info;
clear_siginfo(&info);
info.si_signo = SIGSEGV;
info.si_errno = 0;
info.si_code = SEGV_PKUERR;
info.si_addr = addr;
info.si_pkey = pkey;
return force_sig_info(info.si_signo, &info, current);
}
#endif
/* For the crazy architectures that include trap information in
* the errno field, instead of an actual errno value.
*/
int force_sig_ptrace_errno_trap(int errno, void __user *addr)
{
struct siginfo info;
clear_siginfo(&info);
info.si_signo = SIGTRAP;
info.si_errno = errno;
info.si_code = TRAP_HWBKPT;
info.si_addr = addr;
return force_sig_info(info.si_signo, &info, current);
}
int kill_pgrp(struct pid *pid, int sig, int priv)
{
int ret;
read_lock(&tasklist_lock);
ret = __kill_pgrp_info(sig, __si_special(priv), pid);
read_unlock(&tasklist_lock);
return ret;
}
EXPORT_SYMBOL(kill_pgrp);
int kill_pid(struct pid *pid, int sig, int priv)
{
return kill_pid_info(sig, __si_special(priv), pid);
}
EXPORT_SYMBOL(kill_pid);
/*
* These functions support sending signals using preallocated sigqueue
* structures. This is needed "because realtime applications cannot
* afford to lose notifications of asynchronous events, like timer
* expirations or I/O completions". In the case of POSIX Timers
* we allocate the sigqueue structure from the timer_create. If this
* allocation fails we are able to report the failure to the application
* with an EAGAIN error.
*/
struct sigqueue *sigqueue_alloc(void)
{
struct sigqueue *q = __sigqueue_alloc(-1, current, GFP_KERNEL, 0);
if (q)
q->flags |= SIGQUEUE_PREALLOC;
return q;
}
void sigqueue_free(struct sigqueue *q)
{
unsigned long flags;
2007-08-31 06:56:35 +00:00
spinlock_t *lock = &current->sighand->siglock;
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
/*
* We must hold ->siglock while testing q->list
* to serialize with collect_signal() or with
* __exit_signal()->flush_sigqueue().
*/
2007-08-31 06:56:35 +00:00
spin_lock_irqsave(lock, flags);
q->flags &= ~SIGQUEUE_PREALLOC;
/*
* If it is queued it will be freed when dequeued,
* like the "regular" sigqueue.
*/
2007-08-31 06:56:35 +00:00
if (!list_empty(&q->list))
q = NULL;
2007-08-31 06:56:35 +00:00
spin_unlock_irqrestore(lock, flags);
if (q)
__sigqueue_free(q);
}
int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
2008-04-30 07:52:41 +00:00
{
int sig = q->info.si_signo;
struct sigpending *pending;
unsigned long flags;
int ret, result;
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
ret = -1;
if (!likely(lock_task_sighand(t, &flags)))
goto ret;
ret = 1; /* the signal is ignored */
result = TRACE_SIGNAL_IGNORED;
if (!prepare_signal(sig, t, false))
goto out;
ret = 0;
2008-04-30 07:52:41 +00:00
if (unlikely(!list_empty(&q->list))) {
/*
* If an SI_TIMER entry is already queue just increment
* the overrun count.
*/
BUG_ON(q->info.si_code != SI_TIMER);
q->info.si_overrun++;
result = TRACE_SIGNAL_ALREADY_PENDING;
goto out;
2008-04-30 07:52:41 +00:00
}
posix-timers: fix posix_timer_event() vs dequeue_signal() race The bug was reported and analysed by Mark McLoughlin <markmc@redhat.com>, the patch is based on his and Roland's suggestions. posix_timer_event() always rewrites the pre-allocated siginfo before sending the signal. Most of the written info is the same all the time, but memset(0) is very wrong. If ->sigq is queued we can race with collect_signal() which can fail to find this siginfo looking at .si_signo, or copy_siginfo() can copy the wrong .si_code/si_tid/etc. In short, sys_timer_settime() can in fact stop the active timer, or the user can receive the siginfo with the wrong .si_xxx values. Move "memset(->info, 0)" from posix_timer_event() to alloc_posix_timer(), change send_sigqueue() to set .si_overrun = 0 when ->sigq is not queued. It would be nice to move the whole sigq->info initialization from send to create path, but this is not easy to do without uglifying timer_create() further. As Roland rightly pointed out, we need more cleanups/fixes here, see the "FIXME" comment in the patch. Hopefully this patch makes sense anyway, and it can mask the most bad implications. Reported-by: Mark McLoughlin <markmc@redhat.com> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Mark McLoughlin <markmc@redhat.com> Cc: Oliver Pinter <oliver.pntr@gmail.com> Cc: Roland McGrath <roland@redhat.com> Cc: stable@kernel.org Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> kernel/posix-timers.c | 17 +++++++++++++---- kernel/signal.c | 1 + 2 files changed, 14 insertions(+), 4 deletions(-)
2008-07-23 16:52:05 +00:00
q->info.si_overrun = 0;
2008-04-30 07:52:41 +00:00
signalfd_notify(t, sig);
pending = group ? &t->signal->shared_pending : &t->pending;
2008-04-30 07:52:41 +00:00
list_add_tail(&q->list, &pending->list);
sigaddset(&pending->signal, sig);
complete_signal(sig, t, group);
result = TRACE_SIGNAL_DELIVERED;
out:
trace_signal_generate(sig, &q->info, t, group, result);
unlock_task_sighand(t, &flags);
ret:
return ret;
2008-04-30 07:52:41 +00:00
}
/*
* Let a parent know about the death of a child.
* For a stopped/continued status change, use do_notify_parent_cldstop instead.
*
* Returns true if our parent ignored us and so we've switched to
* self-reaping.
*/
bool do_notify_parent(struct task_struct *tsk, int sig)
{
struct siginfo info;
unsigned long flags;
struct sighand_struct *psig;
bool autoreap = false;
u64 utime, stime;
BUG_ON(sig == -1);
/* do_notify_parent_cldstop should have been called instead. */
BUG_ON(task_is_stopped_or_traced(tsk));
BUG_ON(!tsk->ptrace &&
(tsk->group_leader != tsk || !thread_group_empty(tsk)));
if (sig != SIGCHLD) {
/*
* This is only possible if parent == real_parent.
* Check if it has changed security domain.
*/
if (tsk->parent_exec_id != tsk->parent->self_exec_id)
sig = SIGCHLD;
}
clear_siginfo(&info);
info.si_signo = sig;
info.si_errno = 0;
/*
* We are under tasklist_lock here so our parent is tied to
* us and cannot change.
*
* task_active_pid_ns will always return the same pid namespace
* until a task passes through release_task.
*
* write_lock() currently calls preempt_disable() which is the
* same as rcu_read_lock(), but according to Oleg, this is not
* correct to rely on this
*/
rcu_read_lock();
info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(tsk->parent));
info.si_uid = from_kuid_munged(task_cred_xxx(tsk->parent, user_ns),
task_uid(tsk));
rcu_read_unlock();
task_cputime(tsk, &utime, &stime);
info.si_utime = nsec_to_clock_t(utime + tsk->signal->utime);
info.si_stime = nsec_to_clock_t(stime + tsk->signal->stime);
info.si_status = tsk->exit_code & 0x7f;
if (tsk->exit_code & 0x80)
info.si_code = CLD_DUMPED;
else if (tsk->exit_code & 0x7f)
info.si_code = CLD_KILLED;
else {
info.si_code = CLD_EXITED;
info.si_status = tsk->exit_code >> 8;
}
psig = tsk->parent->sighand;
spin_lock_irqsave(&psig->siglock, flags);
if (!tsk->ptrace && sig == SIGCHLD &&
(psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
(psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) {
/*
* We are exiting and our parent doesn't care. POSIX.1
* defines special semantics for setting SIGCHLD to SIG_IGN
* or setting the SA_NOCLDWAIT flag: we should be reaped
* automatically and not left for our parent's wait4 call.
* Rather than having the parent do it as a magic kind of
* signal handler, we just set this to tell do_exit that we
* can be cleaned up without becoming a zombie. Note that
* we still call __wake_up_parent in this case, because a
* blocked sys_wait4 might now return -ECHILD.
*
* Whether we send SIGCHLD or not for SA_NOCLDWAIT
* is implementation-defined: we do (if you don't want
* it, just use SIG_IGN instead).
*/
autoreap = true;
if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
sig = 0;
}
if (valid_signal(sig) && sig)
__group_send_sig_info(sig, &info, tsk->parent);
__wake_up_parent(tsk, tsk->parent);
spin_unlock_irqrestore(&psig->siglock, flags);
return autoreap;
}
/**
* do_notify_parent_cldstop - notify parent of stopped/continued state change
* @tsk: task reporting the state change
* @for_ptracer: the notification is for ptracer
* @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report
*
* Notify @tsk's parent that the stopped/continued state has changed. If
* @for_ptracer is %false, @tsk's group leader notifies to its real parent.
* If %true, @tsk reports to @tsk->parent which should be the ptracer.
*
* CONTEXT:
* Must be called with tasklist_lock at least read locked.
*/
static void do_notify_parent_cldstop(struct task_struct *tsk,
bool for_ptracer, int why)
{
struct siginfo info;
unsigned long flags;
struct task_struct *parent;
struct sighand_struct *sighand;
u64 utime, stime;
if (for_ptracer) {
parent = tsk->parent;
} else {
tsk = tsk->group_leader;
parent = tsk->real_parent;
}
clear_siginfo(&info);
info.si_signo = SIGCHLD;
info.si_errno = 0;
/*
* see comment in do_notify_parent() about the following 4 lines
*/
rcu_read_lock();
info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(parent));
info.si_uid = from_kuid_munged(task_cred_xxx(parent, user_ns), task_uid(tsk));
rcu_read_unlock();
task_cputime(tsk, &utime, &stime);
info.si_utime = nsec_to_clock_t(utime);
info.si_stime = nsec_to_clock_t(stime);
info.si_code = why;
switch (why) {
case CLD_CONTINUED:
info.si_status = SIGCONT;
break;
case CLD_STOPPED:
info.si_status = tsk->signal->group_exit_code & 0x7f;
break;
case CLD_TRAPPED:
info.si_status = tsk->exit_code & 0x7f;
break;
default:
BUG();
}
sighand = parent->sighand;
spin_lock_irqsave(&sighand->siglock, flags);
if (sighand->action[SIGCHLD-1].sa.sa_handler != SIG_IGN &&
!(sighand->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
__group_send_sig_info(SIGCHLD, &info, parent);
/*
* Even if SIGCHLD is not generated, we must wake up wait4 calls.
*/
__wake_up_parent(tsk, parent);
spin_unlock_irqrestore(&sighand->siglock, flags);
}
static inline int may_ptrace_stop(void)
{
if (!likely(current->ptrace))
return 0;
/*
* Are we in the middle of do_coredump?
* If so and our tracer is also part of the coredump stopping
* is a deadlock situation, and pointless because our tracer
* is dead so don't allow us to stop.
* If SIGKILL was already sent before the caller unlocked
* ->siglock we must see ->core_state != NULL. Otherwise it
* is safe to enter schedule().
*
* This is almost outdated, a task with the pending SIGKILL can't
* block in TASK_TRACED. But PTRACE_EVENT_EXIT can be reported
* after SIGKILL was already dequeued.
*/
if (unlikely(current->mm->core_state) &&
unlikely(current->mm == current->parent->mm))
return 0;
return 1;
}
/*
* Return non-zero if there is a SIGKILL that should be waking us up.
* Called with the siglock held.
*/
static int sigkill_pending(struct task_struct *tsk)
{
return sigismember(&tsk->pending.signal, SIGKILL) ||
sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
}
/*
* This must be called with current->sighand->siglock held.
*
* This should be the path for all ptrace stops.
* We always set current->last_siginfo while stopped here.
* That makes it a way to test a stopped process for
* being ptrace-stopped vs being job-control-stopped.
*
* If we actually decide not to stop at all because the tracer
* is gone, we keep current->exit_code unless clear_code.
*/
static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
__releases(&current->sighand->siglock)
__acquires(&current->sighand->siglock)
{
job control: Notify the real parent of job control events regardless of ptrace With recent changes, job control and ptrace stopped states are properly separated and accessible to the real parent and the ptracer respectively; however, notifications of job control stopped/continued events to the real parent while ptraced are still missing. A ptracee participates in group stop in ptrace_stop() but the completion isn't notified. If participation results in completion of group stop, notify the real parent of the event. The ptrace and group stops are separate and can be handled as such. However, when the real parent and the ptracer are in the same thread group, only the ptrace stop event is visible through wait(2) and the duplicate notifications are different from the current behavior and are confusing. Suppress group stop notification in such cases. The continued state is shared between the real parent and the ptracer but is only meaningful to the real parent. Always notify the real parent and notify the ptracer too for backward compatibility. Similar to stop notification, if the real parent is the ptracer, suppress a duplicate notification. Test case follows. #include <stdio.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <sys/types.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { const struct timespec ts100ms = { .tv_nsec = 100000000 }; pid_t tracee, tracer; siginfo_t si; int i; tracee = fork(); if (tracee == 0) { while (1) { printf("tracee: SIGSTOP\n"); raise(SIGSTOP); nanosleep(&ts100ms, NULL); printf("tracee: SIGCONT\n"); raise(SIGCONT); nanosleep(&ts100ms, NULL); } } waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG | WNOWAIT); tracer = fork(); if (tracer == 0) { nanosleep(&ts100ms, NULL); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); for (i = 0; i < 11; i++) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED); if (si.si_pid && si.si_code == CLD_TRAPPED) ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); } printf("tracer: EXITING\n"); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WCONTINUED | WEXITED); if (si.si_pid) printf("mommy : WAIT status=%02d code=%02d\n", si.si_status, si.si_code); } return 0; } Before this patch, while ptraced, the real parent doesn't get notifications for job control events, so although it can access those events, the later waitid(2) call never wakes up. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C After this patch, it works as expected. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C -v2: Oleg pointed out that * Group stop notification to the real parent should also happen when ptracer detach races with ptrace_stop(). * real_parent_is_ptracer() should be testing thread group equality not the task itself as wait(2) and stop/cont notifications are normally thread-group wide. Both issues are fixed accordingly. -v3: real_parent_is_ptracer() updated to test child->real_parent instead of child->group_leader->real_parent per Oleg's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
bool gstop_done = false;
if (arch_ptrace_stop_needed(exit_code, info)) {
/*
* The arch code has something special to do before a
* ptrace stop. This is allowed to block, e.g. for faults
* on user stack pages. We can't keep the siglock while
* calling arch_ptrace_stop, so we must release it now.
* To preserve proper semantics, we must do this before
* any signal bookkeeping like checking group_stop_count.
* Meanwhile, a SIGKILL could come in before we retake the
* siglock. That must prevent us from sleeping in TASK_TRACED.
* So after regaining the lock, we must check for SIGKILL.
*/
spin_unlock_irq(&current->sighand->siglock);
arch_ptrace_stop(exit_code, info);
spin_lock_irq(&current->sighand->siglock);
if (sigkill_pending(current))
return;
}
set_special_state(TASK_TRACED);
/*
* We're committing to trapping. TRACED should be visible before
* TRAPPING is cleared; otherwise, the tracer might fail do_wait().
* Also, transition to TRACED and updates to ->jobctl should be
* atomic with respect to siglock and should be done after the arch
* hook as siglock is released and regrabbed across it.
*
* TRACER TRACEE
*
* ptrace_attach()
* [L] wait_on_bit(JOBCTL_TRAPPING) [S] set_special_state(TRACED)
* do_wait()
* set_current_state() smp_wmb();
* ptrace_do_wait()
* wait_task_stopped()
* task_stopped_code()
* [L] task_is_traced() [S] task_clear_jobctl_trapping();
*/
smp_wmb();
current->last_siginfo = info;
current->exit_code = exit_code;
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
/*
* If @why is CLD_STOPPED, we're trapping to participate in a group
* stop. Do the bookkeeping. Note that if SIGCONT was delievered
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
* across siglock relocks since INTERRUPT was scheduled, PENDING
* could be clear now. We act as if SIGCONT is received after
* TASK_TRACED is entered - ignore it.
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
*/
if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING))
job control: Notify the real parent of job control events regardless of ptrace With recent changes, job control and ptrace stopped states are properly separated and accessible to the real parent and the ptracer respectively; however, notifications of job control stopped/continued events to the real parent while ptraced are still missing. A ptracee participates in group stop in ptrace_stop() but the completion isn't notified. If participation results in completion of group stop, notify the real parent of the event. The ptrace and group stops are separate and can be handled as such. However, when the real parent and the ptracer are in the same thread group, only the ptrace stop event is visible through wait(2) and the duplicate notifications are different from the current behavior and are confusing. Suppress group stop notification in such cases. The continued state is shared between the real parent and the ptracer but is only meaningful to the real parent. Always notify the real parent and notify the ptracer too for backward compatibility. Similar to stop notification, if the real parent is the ptracer, suppress a duplicate notification. Test case follows. #include <stdio.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <sys/types.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { const struct timespec ts100ms = { .tv_nsec = 100000000 }; pid_t tracee, tracer; siginfo_t si; int i; tracee = fork(); if (tracee == 0) { while (1) { printf("tracee: SIGSTOP\n"); raise(SIGSTOP); nanosleep(&ts100ms, NULL); printf("tracee: SIGCONT\n"); raise(SIGCONT); nanosleep(&ts100ms, NULL); } } waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG | WNOWAIT); tracer = fork(); if (tracer == 0) { nanosleep(&ts100ms, NULL); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); for (i = 0; i < 11; i++) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED); if (si.si_pid && si.si_code == CLD_TRAPPED) ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); } printf("tracer: EXITING\n"); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WCONTINUED | WEXITED); if (si.si_pid) printf("mommy : WAIT status=%02d code=%02d\n", si.si_status, si.si_code); } return 0; } Before this patch, while ptraced, the real parent doesn't get notifications for job control events, so although it can access those events, the later waitid(2) call never wakes up. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C After this patch, it works as expected. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C -v2: Oleg pointed out that * Group stop notification to the real parent should also happen when ptracer detach races with ptrace_stop(). * real_parent_is_ptracer() should be testing thread group equality not the task itself as wait(2) and stop/cont notifications are normally thread-group wide. Both issues are fixed accordingly. -v3: real_parent_is_ptracer() updated to test child->real_parent instead of child->group_leader->real_parent per Oleg's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
gstop_done = task_participate_group_stop(current);
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
ptrace: implement TRAP_NOTIFY and use it for group stop events Currently there's no way for ptracer to find out whether group stop finished other than polling with INTERRUPT - GETSIGINFO - CONT sequence. This patch implements group stop notification for ptracer using STOP traps. When group stop state of a seized tracee changes, JOBCTL_TRAP_NOTIFY is set, which schedules a STOP trap which is sticky - it isn't cleared by other traps and at least one STOP trap will happen eventually. STOP trap is synchronization point for event notification and the tracer can determine the current group stop state by looking at the signal number portion of exit code (si_status from waitid(2) or si_code from PTRACE_GETSIGINFO). Notifications are generated both on start and end of group stops but, because group stop participation always happens before STOP trap, this doesn't cause an extra trap while tracee is participating in group stop. The symmetry will be useful later. Note that this notification works iff tracee is not trapped. Currently there is no way to be notified of group stop state changes while tracee is trapped. This will be addressed by a later patch. An example program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) pause(); tracer = fork(); if (!tracer) { siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); repeat: waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (!si.si_code) { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); goto repeat; } printf("tracer: stopped=%d signo=%d\n", si.si_signo != SIGTRAP, si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, NULL); goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } In the above program, tracer keeps tracee running and gets notification of each group stop state changes. # ./test-notify tracer: stopped=0 signo=5 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:17 +00:00
/* any trap clears pending STOP trap, STOP trap clears NOTIFY */
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
task_clear_jobctl_pending(current, JOBCTL_TRAP_STOP);
ptrace: implement TRAP_NOTIFY and use it for group stop events Currently there's no way for ptracer to find out whether group stop finished other than polling with INTERRUPT - GETSIGINFO - CONT sequence. This patch implements group stop notification for ptracer using STOP traps. When group stop state of a seized tracee changes, JOBCTL_TRAP_NOTIFY is set, which schedules a STOP trap which is sticky - it isn't cleared by other traps and at least one STOP trap will happen eventually. STOP trap is synchronization point for event notification and the tracer can determine the current group stop state by looking at the signal number portion of exit code (si_status from waitid(2) or si_code from PTRACE_GETSIGINFO). Notifications are generated both on start and end of group stops but, because group stop participation always happens before STOP trap, this doesn't cause an extra trap while tracee is participating in group stop. The symmetry will be useful later. Note that this notification works iff tracee is not trapped. Currently there is no way to be notified of group stop state changes while tracee is trapped. This will be addressed by a later patch. An example program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) pause(); tracer = fork(); if (!tracer) { siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); repeat: waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (!si.si_code) { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); goto repeat; } printf("tracer: stopped=%d signo=%d\n", si.si_signo != SIGTRAP, si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, NULL); goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } In the above program, tracer keeps tracee running and gets notification of each group stop state changes. # ./test-notify tracer: stopped=0 signo=5 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:17 +00:00
if (info && info->si_code >> 8 == PTRACE_EVENT_STOP)
task_clear_jobctl_pending(current, JOBCTL_TRAP_NOTIFY);
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
/* entering a trap, clear TRAPPING */
task_clear_jobctl_trapping(current);
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
spin_unlock_irq(&current->sighand->siglock);
read_lock(&tasklist_lock);
if (may_ptrace_stop()) {
job control: Notify the real parent of job control events regardless of ptrace With recent changes, job control and ptrace stopped states are properly separated and accessible to the real parent and the ptracer respectively; however, notifications of job control stopped/continued events to the real parent while ptraced are still missing. A ptracee participates in group stop in ptrace_stop() but the completion isn't notified. If participation results in completion of group stop, notify the real parent of the event. The ptrace and group stops are separate and can be handled as such. However, when the real parent and the ptracer are in the same thread group, only the ptrace stop event is visible through wait(2) and the duplicate notifications are different from the current behavior and are confusing. Suppress group stop notification in such cases. The continued state is shared between the real parent and the ptracer but is only meaningful to the real parent. Always notify the real parent and notify the ptracer too for backward compatibility. Similar to stop notification, if the real parent is the ptracer, suppress a duplicate notification. Test case follows. #include <stdio.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <sys/types.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { const struct timespec ts100ms = { .tv_nsec = 100000000 }; pid_t tracee, tracer; siginfo_t si; int i; tracee = fork(); if (tracee == 0) { while (1) { printf("tracee: SIGSTOP\n"); raise(SIGSTOP); nanosleep(&ts100ms, NULL); printf("tracee: SIGCONT\n"); raise(SIGCONT); nanosleep(&ts100ms, NULL); } } waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG | WNOWAIT); tracer = fork(); if (tracer == 0) { nanosleep(&ts100ms, NULL); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); for (i = 0; i < 11; i++) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED); if (si.si_pid && si.si_code == CLD_TRAPPED) ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); } printf("tracer: EXITING\n"); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WCONTINUED | WEXITED); if (si.si_pid) printf("mommy : WAIT status=%02d code=%02d\n", si.si_status, si.si_code); } return 0; } Before this patch, while ptraced, the real parent doesn't get notifications for job control events, so although it can access those events, the later waitid(2) call never wakes up. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C After this patch, it works as expected. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C -v2: Oleg pointed out that * Group stop notification to the real parent should also happen when ptracer detach races with ptrace_stop(). * real_parent_is_ptracer() should be testing thread group equality not the task itself as wait(2) and stop/cont notifications are normally thread-group wide. Both issues are fixed accordingly. -v3: real_parent_is_ptracer() updated to test child->real_parent instead of child->group_leader->real_parent per Oleg's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
/*
* Notify parents of the stop.
*
* While ptraced, there are two parents - the ptracer and
* the real_parent of the group_leader. The ptracer should
* know about every stop while the real parent is only
* interested in the completion of group stop. The states
* for the two don't interact with each other. Notify
* separately unless they're gonna be duplicates.
*/
do_notify_parent_cldstop(current, true, why);
if (gstop_done && ptrace_reparented(current))
job control: Notify the real parent of job control events regardless of ptrace With recent changes, job control and ptrace stopped states are properly separated and accessible to the real parent and the ptracer respectively; however, notifications of job control stopped/continued events to the real parent while ptraced are still missing. A ptracee participates in group stop in ptrace_stop() but the completion isn't notified. If participation results in completion of group stop, notify the real parent of the event. The ptrace and group stops are separate and can be handled as such. However, when the real parent and the ptracer are in the same thread group, only the ptrace stop event is visible through wait(2) and the duplicate notifications are different from the current behavior and are confusing. Suppress group stop notification in such cases. The continued state is shared between the real parent and the ptracer but is only meaningful to the real parent. Always notify the real parent and notify the ptracer too for backward compatibility. Similar to stop notification, if the real parent is the ptracer, suppress a duplicate notification. Test case follows. #include <stdio.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <sys/types.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { const struct timespec ts100ms = { .tv_nsec = 100000000 }; pid_t tracee, tracer; siginfo_t si; int i; tracee = fork(); if (tracee == 0) { while (1) { printf("tracee: SIGSTOP\n"); raise(SIGSTOP); nanosleep(&ts100ms, NULL); printf("tracee: SIGCONT\n"); raise(SIGCONT); nanosleep(&ts100ms, NULL); } } waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG | WNOWAIT); tracer = fork(); if (tracer == 0) { nanosleep(&ts100ms, NULL); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); for (i = 0; i < 11; i++) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED); if (si.si_pid && si.si_code == CLD_TRAPPED) ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); } printf("tracer: EXITING\n"); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WCONTINUED | WEXITED); if (si.si_pid) printf("mommy : WAIT status=%02d code=%02d\n", si.si_status, si.si_code); } return 0; } Before this patch, while ptraced, the real parent doesn't get notifications for job control events, so although it can access those events, the later waitid(2) call never wakes up. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C After this patch, it works as expected. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C -v2: Oleg pointed out that * Group stop notification to the real parent should also happen when ptracer detach races with ptrace_stop(). * real_parent_is_ptracer() should be testing thread group equality not the task itself as wait(2) and stop/cont notifications are normally thread-group wide. Both issues are fixed accordingly. -v3: real_parent_is_ptracer() updated to test child->real_parent instead of child->group_leader->real_parent per Oleg's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
do_notify_parent_cldstop(current, false, why);
/*
* Don't want to allow preemption here, because
* sys_ptrace() needs this task to be inactive.
*
* XXX: implement read_unlock_no_resched().
*/
preempt_disable();
read_unlock(&tasklist_lock);
preempt_enable_no_resched();
freezable_schedule();
} else {
/*
* By the time we got the lock, our tracer went away.
* Don't drop the lock yet, another tracer may come.
job control: Notify the real parent of job control events regardless of ptrace With recent changes, job control and ptrace stopped states are properly separated and accessible to the real parent and the ptracer respectively; however, notifications of job control stopped/continued events to the real parent while ptraced are still missing. A ptracee participates in group stop in ptrace_stop() but the completion isn't notified. If participation results in completion of group stop, notify the real parent of the event. The ptrace and group stops are separate and can be handled as such. However, when the real parent and the ptracer are in the same thread group, only the ptrace stop event is visible through wait(2) and the duplicate notifications are different from the current behavior and are confusing. Suppress group stop notification in such cases. The continued state is shared between the real parent and the ptracer but is only meaningful to the real parent. Always notify the real parent and notify the ptracer too for backward compatibility. Similar to stop notification, if the real parent is the ptracer, suppress a duplicate notification. Test case follows. #include <stdio.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <sys/types.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { const struct timespec ts100ms = { .tv_nsec = 100000000 }; pid_t tracee, tracer; siginfo_t si; int i; tracee = fork(); if (tracee == 0) { while (1) { printf("tracee: SIGSTOP\n"); raise(SIGSTOP); nanosleep(&ts100ms, NULL); printf("tracee: SIGCONT\n"); raise(SIGCONT); nanosleep(&ts100ms, NULL); } } waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG | WNOWAIT); tracer = fork(); if (tracer == 0) { nanosleep(&ts100ms, NULL); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); for (i = 0; i < 11; i++) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED); if (si.si_pid && si.si_code == CLD_TRAPPED) ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); } printf("tracer: EXITING\n"); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WCONTINUED | WEXITED); if (si.si_pid) printf("mommy : WAIT status=%02d code=%02d\n", si.si_status, si.si_code); } return 0; } Before this patch, while ptraced, the real parent doesn't get notifications for job control events, so although it can access those events, the later waitid(2) call never wakes up. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C After this patch, it works as expected. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C -v2: Oleg pointed out that * Group stop notification to the real parent should also happen when ptracer detach races with ptrace_stop(). * real_parent_is_ptracer() should be testing thread group equality not the task itself as wait(2) and stop/cont notifications are normally thread-group wide. Both issues are fixed accordingly. -v3: real_parent_is_ptracer() updated to test child->real_parent instead of child->group_leader->real_parent per Oleg's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
*
* If @gstop_done, the ptracer went away between group stop
* completion and here. During detach, it would have set
* JOBCTL_STOP_PENDING on us and we'll re-enter
* TASK_STOPPED in do_signal_stop() on return, so notifying
* the real parent of the group stop completion is enough.
*/
job control: Notify the real parent of job control events regardless of ptrace With recent changes, job control and ptrace stopped states are properly separated and accessible to the real parent and the ptracer respectively; however, notifications of job control stopped/continued events to the real parent while ptraced are still missing. A ptracee participates in group stop in ptrace_stop() but the completion isn't notified. If participation results in completion of group stop, notify the real parent of the event. The ptrace and group stops are separate and can be handled as such. However, when the real parent and the ptracer are in the same thread group, only the ptrace stop event is visible through wait(2) and the duplicate notifications are different from the current behavior and are confusing. Suppress group stop notification in such cases. The continued state is shared between the real parent and the ptracer but is only meaningful to the real parent. Always notify the real parent and notify the ptracer too for backward compatibility. Similar to stop notification, if the real parent is the ptracer, suppress a duplicate notification. Test case follows. #include <stdio.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <sys/types.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { const struct timespec ts100ms = { .tv_nsec = 100000000 }; pid_t tracee, tracer; siginfo_t si; int i; tracee = fork(); if (tracee == 0) { while (1) { printf("tracee: SIGSTOP\n"); raise(SIGSTOP); nanosleep(&ts100ms, NULL); printf("tracee: SIGCONT\n"); raise(SIGCONT); nanosleep(&ts100ms, NULL); } } waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG | WNOWAIT); tracer = fork(); if (tracer == 0) { nanosleep(&ts100ms, NULL); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); for (i = 0; i < 11; i++) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED); if (si.si_pid && si.si_code == CLD_TRAPPED) ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); } printf("tracer: EXITING\n"); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WCONTINUED | WEXITED); if (si.si_pid) printf("mommy : WAIT status=%02d code=%02d\n", si.si_status, si.si_code); } return 0; } Before this patch, while ptraced, the real parent doesn't get notifications for job control events, so although it can access those events, the later waitid(2) call never wakes up. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C After this patch, it works as expected. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C -v2: Oleg pointed out that * Group stop notification to the real parent should also happen when ptracer detach races with ptrace_stop(). * real_parent_is_ptracer() should be testing thread group equality not the task itself as wait(2) and stop/cont notifications are normally thread-group wide. Both issues are fixed accordingly. -v3: real_parent_is_ptracer() updated to test child->real_parent instead of child->group_leader->real_parent per Oleg's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
if (gstop_done)
do_notify_parent_cldstop(current, false, why);
/* tasklist protects us from ptrace_freeze_traced() */
__set_current_state(TASK_RUNNING);
if (clear_code)
current->exit_code = 0;
read_unlock(&tasklist_lock);
}
/*
* We are back. Now reacquire the siglock before touching
* last_siginfo, so that we are sure to have synchronized with
* any signal-sending on another CPU that wants to examine it.
*/
spin_lock_irq(&current->sighand->siglock);
current->last_siginfo = NULL;
ptrace: implement PTRACE_LISTEN The previous patch implemented async notification for ptrace but it only worked while trace is running. This patch introduces PTRACE_LISTEN which is suggested by Oleg Nestrov. It's allowed iff tracee is in STOP trap and puts tracee into quasi-running state - tracee never really runs but wait(2) and ptrace(2) consider it to be running. While ptracer is listening, tracee is allowed to re-enter STOP to notify an async event. Listening state is cleared on the first notification. Ptracer can also clear it by issuing INTERRUPT - tracee will re-trap into STOP with listening state cleared. This allows ptracer to monitor group stop state without running tracee - use INTERRUPT to put tracee into STOP trap, issue LISTEN and then wait(2) to wait for the next group stop event. When it happens, PTRACE_GETSIGINFO provides information to determine the current state. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_LISTEN 0x4208 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) pause(); tracer = fork(); if (!tracer) { siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); repeat: waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (!si.si_code) { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); goto repeat; } printf("tracer: stopped=%d signo=%d\n", si.si_signo != SIGTRAP, si.si_signo); if (si.si_signo != SIGTRAP) ptrace(PTRACE_LISTEN, tracee, NULL, NULL); else ptrace(PTRACE_CONT, tracee, NULL, NULL); goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } This is identical to the program to test TRAP_NOTIFY except that tracee is PTRACE_LISTEN'd instead of PTRACE_CONT'd when group stopped. This allows ptracer to monitor when group stop ends without running tracee. # ./test-listen tracer: stopped=0 signo=5 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 -v2: Moved JOBCTL_LISTENING check in wait_task_stopped() into task_stopped_code() as suggested by Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:18 +00:00
/* LISTENING can be set only during STOP traps, clear it */
current->jobctl &= ~JOBCTL_LISTENING;
/*
* Queued signals ignored us while we were stopped for tracing.
* So check for any that we should take before resuming user mode.
* This sets TIF_SIGPENDING, but never clears it.
*/
recalc_sigpending_tsk(current);
}
ptrace: implement PTRACE_SEIZE PTRACE_ATTACH implicitly issues SIGSTOP on attach which has side effects on tracee signal and job control states. This patch implements a new ptrace request PTRACE_SEIZE which attaches a tracee without trapping it or affecting its signal and job control states. The usage is the same with PTRACE_ATTACH but it takes PTRACE_SEIZE_* flags in @data. Currently, the only defined flag is PTRACE_SEIZE_DEVEL which is a temporary flag to enable PTRACE_SEIZE. PTRACE_SEIZE will change ptrace behaviors outside of attach itself. The changes will be implemented gradually and the DEVEL flag is to prevent programs which expect full SEIZE behavior from using it before all the behavior modifications are complete while allowing unit testing. The flag will be removed once SEIZE behaviors are completely implemented. * PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After attaching tracee continues to run unless a trap condition occurs. * PTRACE_SEIZE doesn't affect signal or group stop state. * If PTRACE_SEIZE'd, group stop uses PTRACE_EVENT_STOP trap which uses exit_code of (signr | PTRACE_EVENT_STOP << 8) where signr is one of the stopping signals if group stop is in effect or SIGTRAP otherwise, and returns usual trap siginfo on PTRACE_GETSIGINFO instead of NULL. Seizing sets PT_SEIZED in ->ptrace of the tracee. This flag will be used to determine whether new SEIZE behaviors should be enabled. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static const struct timespec ts1s = { .tv_sec = 1 }; static const struct timespec ts3s = { .tv_sec = 3 }; int main(int argc, char **argv) { pid_t tracee; tracee = fork(); if (tracee == 0) { nanosleep(&ts100ms, NULL); while (1) { printf("tracee: alive\n"); nanosleep(&ts1s, NULL); } } if (argc > 1) kill(tracee, SIGSTOP); nanosleep(&ts100ms, NULL); ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); if (argc > 1) { waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, NULL); } nanosleep(&ts3s, NULL); printf("tracer: exiting\n"); return 0; } When the above program is called w/o argument, tracee is seized while running and remains running. When tracer exits, tracee continues to run and print out messages. # ./test-seize-simple tracee: alive tracee: alive tracee: alive tracer: exiting tracee: alive tracee: alive When called with an argument, tracee is seized from stopped state and continued, and returns to stopped state when tracer exits. # ./test-seize tracee: alive tracee: alive tracee: alive tracer: exiting # ps -el|grep test-seize 1 T 0 4720 1 0 80 0 - 941 signal ttyS0 00:00:00 test-seize -v2: SEIZE doesn't schedule TRAP_STOP and leaves tracee running as Jan suggested. -v3: PTRACE_EVENT_STOP traps now report group stop state by signr. If group stop is in effect the stop signal number is returned as part of exit_code; otherwise, SIGTRAP. This was suggested by Denys and Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:15 +00:00
static void ptrace_do_notify(int signr, int exit_code, int why)
{
siginfo_t info;
clear_siginfo(&info);
ptrace: implement PTRACE_SEIZE PTRACE_ATTACH implicitly issues SIGSTOP on attach which has side effects on tracee signal and job control states. This patch implements a new ptrace request PTRACE_SEIZE which attaches a tracee without trapping it or affecting its signal and job control states. The usage is the same with PTRACE_ATTACH but it takes PTRACE_SEIZE_* flags in @data. Currently, the only defined flag is PTRACE_SEIZE_DEVEL which is a temporary flag to enable PTRACE_SEIZE. PTRACE_SEIZE will change ptrace behaviors outside of attach itself. The changes will be implemented gradually and the DEVEL flag is to prevent programs which expect full SEIZE behavior from using it before all the behavior modifications are complete while allowing unit testing. The flag will be removed once SEIZE behaviors are completely implemented. * PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After attaching tracee continues to run unless a trap condition occurs. * PTRACE_SEIZE doesn't affect signal or group stop state. * If PTRACE_SEIZE'd, group stop uses PTRACE_EVENT_STOP trap which uses exit_code of (signr | PTRACE_EVENT_STOP << 8) where signr is one of the stopping signals if group stop is in effect or SIGTRAP otherwise, and returns usual trap siginfo on PTRACE_GETSIGINFO instead of NULL. Seizing sets PT_SEIZED in ->ptrace of the tracee. This flag will be used to determine whether new SEIZE behaviors should be enabled. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static const struct timespec ts1s = { .tv_sec = 1 }; static const struct timespec ts3s = { .tv_sec = 3 }; int main(int argc, char **argv) { pid_t tracee; tracee = fork(); if (tracee == 0) { nanosleep(&ts100ms, NULL); while (1) { printf("tracee: alive\n"); nanosleep(&ts1s, NULL); } } if (argc > 1) kill(tracee, SIGSTOP); nanosleep(&ts100ms, NULL); ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); if (argc > 1) { waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, NULL); } nanosleep(&ts3s, NULL); printf("tracer: exiting\n"); return 0; } When the above program is called w/o argument, tracee is seized while running and remains running. When tracer exits, tracee continues to run and print out messages. # ./test-seize-simple tracee: alive tracee: alive tracee: alive tracer: exiting tracee: alive tracee: alive When called with an argument, tracee is seized from stopped state and continued, and returns to stopped state when tracer exits. # ./test-seize tracee: alive tracee: alive tracee: alive tracer: exiting # ps -el|grep test-seize 1 T 0 4720 1 0 80 0 - 941 signal ttyS0 00:00:00 test-seize -v2: SEIZE doesn't schedule TRAP_STOP and leaves tracee running as Jan suggested. -v3: PTRACE_EVENT_STOP traps now report group stop state by signr. If group stop is in effect the stop signal number is returned as part of exit_code; otherwise, SIGTRAP. This was suggested by Denys and Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:15 +00:00
info.si_signo = signr;
info.si_code = exit_code;
info.si_pid = task_pid_vnr(current);
info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
/* Let the debugger run. */
ptrace: implement PTRACE_SEIZE PTRACE_ATTACH implicitly issues SIGSTOP on attach which has side effects on tracee signal and job control states. This patch implements a new ptrace request PTRACE_SEIZE which attaches a tracee without trapping it or affecting its signal and job control states. The usage is the same with PTRACE_ATTACH but it takes PTRACE_SEIZE_* flags in @data. Currently, the only defined flag is PTRACE_SEIZE_DEVEL which is a temporary flag to enable PTRACE_SEIZE. PTRACE_SEIZE will change ptrace behaviors outside of attach itself. The changes will be implemented gradually and the DEVEL flag is to prevent programs which expect full SEIZE behavior from using it before all the behavior modifications are complete while allowing unit testing. The flag will be removed once SEIZE behaviors are completely implemented. * PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After attaching tracee continues to run unless a trap condition occurs. * PTRACE_SEIZE doesn't affect signal or group stop state. * If PTRACE_SEIZE'd, group stop uses PTRACE_EVENT_STOP trap which uses exit_code of (signr | PTRACE_EVENT_STOP << 8) where signr is one of the stopping signals if group stop is in effect or SIGTRAP otherwise, and returns usual trap siginfo on PTRACE_GETSIGINFO instead of NULL. Seizing sets PT_SEIZED in ->ptrace of the tracee. This flag will be used to determine whether new SEIZE behaviors should be enabled. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static const struct timespec ts1s = { .tv_sec = 1 }; static const struct timespec ts3s = { .tv_sec = 3 }; int main(int argc, char **argv) { pid_t tracee; tracee = fork(); if (tracee == 0) { nanosleep(&ts100ms, NULL); while (1) { printf("tracee: alive\n"); nanosleep(&ts1s, NULL); } } if (argc > 1) kill(tracee, SIGSTOP); nanosleep(&ts100ms, NULL); ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); if (argc > 1) { waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, NULL); } nanosleep(&ts3s, NULL); printf("tracer: exiting\n"); return 0; } When the above program is called w/o argument, tracee is seized while running and remains running. When tracer exits, tracee continues to run and print out messages. # ./test-seize-simple tracee: alive tracee: alive tracee: alive tracer: exiting tracee: alive tracee: alive When called with an argument, tracee is seized from stopped state and continued, and returns to stopped state when tracer exits. # ./test-seize tracee: alive tracee: alive tracee: alive tracer: exiting # ps -el|grep test-seize 1 T 0 4720 1 0 80 0 - 941 signal ttyS0 00:00:00 test-seize -v2: SEIZE doesn't schedule TRAP_STOP and leaves tracee running as Jan suggested. -v3: PTRACE_EVENT_STOP traps now report group stop state by signr. If group stop is in effect the stop signal number is returned as part of exit_code; otherwise, SIGTRAP. This was suggested by Denys and Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:15 +00:00
ptrace_stop(exit_code, why, 1, &info);
}
void ptrace_notify(int exit_code)
{
BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
if (unlikely(current->task_works))
task_work_run();
ptrace: implement PTRACE_SEIZE PTRACE_ATTACH implicitly issues SIGSTOP on attach which has side effects on tracee signal and job control states. This patch implements a new ptrace request PTRACE_SEIZE which attaches a tracee without trapping it or affecting its signal and job control states. The usage is the same with PTRACE_ATTACH but it takes PTRACE_SEIZE_* flags in @data. Currently, the only defined flag is PTRACE_SEIZE_DEVEL which is a temporary flag to enable PTRACE_SEIZE. PTRACE_SEIZE will change ptrace behaviors outside of attach itself. The changes will be implemented gradually and the DEVEL flag is to prevent programs which expect full SEIZE behavior from using it before all the behavior modifications are complete while allowing unit testing. The flag will be removed once SEIZE behaviors are completely implemented. * PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After attaching tracee continues to run unless a trap condition occurs. * PTRACE_SEIZE doesn't affect signal or group stop state. * If PTRACE_SEIZE'd, group stop uses PTRACE_EVENT_STOP trap which uses exit_code of (signr | PTRACE_EVENT_STOP << 8) where signr is one of the stopping signals if group stop is in effect or SIGTRAP otherwise, and returns usual trap siginfo on PTRACE_GETSIGINFO instead of NULL. Seizing sets PT_SEIZED in ->ptrace of the tracee. This flag will be used to determine whether new SEIZE behaviors should be enabled. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static const struct timespec ts1s = { .tv_sec = 1 }; static const struct timespec ts3s = { .tv_sec = 3 }; int main(int argc, char **argv) { pid_t tracee; tracee = fork(); if (tracee == 0) { nanosleep(&ts100ms, NULL); while (1) { printf("tracee: alive\n"); nanosleep(&ts1s, NULL); } } if (argc > 1) kill(tracee, SIGSTOP); nanosleep(&ts100ms, NULL); ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); if (argc > 1) { waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, NULL); } nanosleep(&ts3s, NULL); printf("tracer: exiting\n"); return 0; } When the above program is called w/o argument, tracee is seized while running and remains running. When tracer exits, tracee continues to run and print out messages. # ./test-seize-simple tracee: alive tracee: alive tracee: alive tracer: exiting tracee: alive tracee: alive When called with an argument, tracee is seized from stopped state and continued, and returns to stopped state when tracer exits. # ./test-seize tracee: alive tracee: alive tracee: alive tracer: exiting # ps -el|grep test-seize 1 T 0 4720 1 0 80 0 - 941 signal ttyS0 00:00:00 test-seize -v2: SEIZE doesn't schedule TRAP_STOP and leaves tracee running as Jan suggested. -v3: PTRACE_EVENT_STOP traps now report group stop state by signr. If group stop is in effect the stop signal number is returned as part of exit_code; otherwise, SIGTRAP. This was suggested by Denys and Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:15 +00:00
spin_lock_irq(&current->sighand->siglock);
ptrace: implement PTRACE_SEIZE PTRACE_ATTACH implicitly issues SIGSTOP on attach which has side effects on tracee signal and job control states. This patch implements a new ptrace request PTRACE_SEIZE which attaches a tracee without trapping it or affecting its signal and job control states. The usage is the same with PTRACE_ATTACH but it takes PTRACE_SEIZE_* flags in @data. Currently, the only defined flag is PTRACE_SEIZE_DEVEL which is a temporary flag to enable PTRACE_SEIZE. PTRACE_SEIZE will change ptrace behaviors outside of attach itself. The changes will be implemented gradually and the DEVEL flag is to prevent programs which expect full SEIZE behavior from using it before all the behavior modifications are complete while allowing unit testing. The flag will be removed once SEIZE behaviors are completely implemented. * PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After attaching tracee continues to run unless a trap condition occurs. * PTRACE_SEIZE doesn't affect signal or group stop state. * If PTRACE_SEIZE'd, group stop uses PTRACE_EVENT_STOP trap which uses exit_code of (signr | PTRACE_EVENT_STOP << 8) where signr is one of the stopping signals if group stop is in effect or SIGTRAP otherwise, and returns usual trap siginfo on PTRACE_GETSIGINFO instead of NULL. Seizing sets PT_SEIZED in ->ptrace of the tracee. This flag will be used to determine whether new SEIZE behaviors should be enabled. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static const struct timespec ts1s = { .tv_sec = 1 }; static const struct timespec ts3s = { .tv_sec = 3 }; int main(int argc, char **argv) { pid_t tracee; tracee = fork(); if (tracee == 0) { nanosleep(&ts100ms, NULL); while (1) { printf("tracee: alive\n"); nanosleep(&ts1s, NULL); } } if (argc > 1) kill(tracee, SIGSTOP); nanosleep(&ts100ms, NULL); ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); if (argc > 1) { waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, NULL); } nanosleep(&ts3s, NULL); printf("tracer: exiting\n"); return 0; } When the above program is called w/o argument, tracee is seized while running and remains running. When tracer exits, tracee continues to run and print out messages. # ./test-seize-simple tracee: alive tracee: alive tracee: alive tracer: exiting tracee: alive tracee: alive When called with an argument, tracee is seized from stopped state and continued, and returns to stopped state when tracer exits. # ./test-seize tracee: alive tracee: alive tracee: alive tracer: exiting # ps -el|grep test-seize 1 T 0 4720 1 0 80 0 - 941 signal ttyS0 00:00:00 test-seize -v2: SEIZE doesn't schedule TRAP_STOP and leaves tracee running as Jan suggested. -v3: PTRACE_EVENT_STOP traps now report group stop state by signr. If group stop is in effect the stop signal number is returned as part of exit_code; otherwise, SIGTRAP. This was suggested by Denys and Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:15 +00:00
ptrace_do_notify(SIGTRAP, exit_code, CLD_TRAPPED);
spin_unlock_irq(&current->sighand->siglock);
}
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
/**
* do_signal_stop - handle group stop for SIGSTOP and other stop signals
* @signr: signr causing group stop if initiating
*
* If %JOBCTL_STOP_PENDING is not set yet, initiate group stop with @signr
* and participate in it. If already set, participate in the existing
* group stop. If participated in a group stop (and thus slept), %true is
* returned with siglock released.
*
* If ptraced, this function doesn't handle stop itself. Instead,
* %JOBCTL_TRAP_STOP is scheduled and %false is returned with siglock
* untouched. The caller must ensure that INTERRUPT trap handling takes
* places afterwards.
*
* CONTEXT:
* Must be called with @current->sighand->siglock held, which is released
* on %true return.
*
* RETURNS:
* %false if group stop is already cancelled or ptrace trap is scheduled.
* %true if participated in group stop.
*/
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
static bool do_signal_stop(int signr)
__releases(&current->sighand->siglock)
{
struct signal_struct *sig = current->signal;
if (!(current->jobctl & JOBCTL_STOP_PENDING)) {
unsigned long gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
struct task_struct *t;
/* signr will be recorded in task->jobctl for retries */
WARN_ON_ONCE(signr & ~JOBCTL_STOP_SIGMASK);
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
if (!likely(current->jobctl & JOBCTL_STOP_DEQUEUED) ||
unlikely(signal_group_exit(sig)))
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
return false;
/*
job control: Don't set group_stop exit_code if re-entering job control stop While ptraced, a task may be resumed while the containing process is still job control stopped. If the task receives another stop signal in this state, it will still initiate group stop, which generates group_exit_code, which the real parent would be able to see once the ptracer detaches. In this scenario, the real parent may see two consecutive CLD_STOPPED events from two stop signals without intervening SIGCONT, which normally is impossible. Test case follows. #include <stdio.h> #include <unistd.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { pid_t tracee; siginfo_t si; tracee = fork(); if (!tracee) while (1) pause(); kill(tracee, SIGSTOP); waitid(P_PID, tracee, &si, WSTOPPED); if (!fork()) { ptrace(PTRACE_ATTACH, tracee, NULL, NULL); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_DETACH, tracee, NULL, NULL); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG); if (si.si_pid) printf("st=%02d c=%02d\n", si.si_status, si.si_code); } return 0; } Before the patch, the latter waitid() in polling mode reports the second stopped event generated by the implied SIGSTOP of PTRACE_ATTACH. st=19 c=05 ^C After the patch, the second event is not reported. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
* There is no group stop already in progress. We must
* initiate one now.
*
* While ptraced, a task may be resumed while group stop is
* still in effect and then receive a stop signal and
* initiate another group stop. This deviates from the
* usual behavior as two consecutive stop signals can't
* cause two group stops when !ptraced. That is why we
* also check !task_is_stopped(t) below.
job control: Don't set group_stop exit_code if re-entering job control stop While ptraced, a task may be resumed while the containing process is still job control stopped. If the task receives another stop signal in this state, it will still initiate group stop, which generates group_exit_code, which the real parent would be able to see once the ptracer detaches. In this scenario, the real parent may see two consecutive CLD_STOPPED events from two stop signals without intervening SIGCONT, which normally is impossible. Test case follows. #include <stdio.h> #include <unistd.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { pid_t tracee; siginfo_t si; tracee = fork(); if (!tracee) while (1) pause(); kill(tracee, SIGSTOP); waitid(P_PID, tracee, &si, WSTOPPED); if (!fork()) { ptrace(PTRACE_ATTACH, tracee, NULL, NULL); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_DETACH, tracee, NULL, NULL); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG); if (si.si_pid) printf("st=%02d c=%02d\n", si.si_status, si.si_code); } return 0; } Before the patch, the latter waitid() in polling mode reports the second stopped event generated by the implied SIGSTOP of PTRACE_ATTACH. st=19 c=05 ^C After the patch, the second event is not reported. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
*
* The condition can be distinguished by testing whether
* SIGNAL_STOP_STOPPED is already set. Don't generate
* group_exit_code in such case.
*
* This is not necessary for SIGNAL_STOP_CONTINUED because
* an intervening stop signal is required to cause two
* continued events regardless of ptrace.
*/
job control: Don't set group_stop exit_code if re-entering job control stop While ptraced, a task may be resumed while the containing process is still job control stopped. If the task receives another stop signal in this state, it will still initiate group stop, which generates group_exit_code, which the real parent would be able to see once the ptracer detaches. In this scenario, the real parent may see two consecutive CLD_STOPPED events from two stop signals without intervening SIGCONT, which normally is impossible. Test case follows. #include <stdio.h> #include <unistd.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { pid_t tracee; siginfo_t si; tracee = fork(); if (!tracee) while (1) pause(); kill(tracee, SIGSTOP); waitid(P_PID, tracee, &si, WSTOPPED); if (!fork()) { ptrace(PTRACE_ATTACH, tracee, NULL, NULL); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); waitid(P_PID, tracee, &si, WSTOPPED); ptrace(PTRACE_DETACH, tracee, NULL, NULL); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG); if (si.si_pid) printf("st=%02d c=%02d\n", si.si_status, si.si_code); } return 0; } Before the patch, the latter waitid() in polling mode reports the second stopped event generated by the implied SIGSTOP of PTRACE_ATTACH. st=19 c=05 ^C After the patch, the second event is not reported. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
if (!(sig->flags & SIGNAL_STOP_STOPPED))
sig->group_exit_code = signr;
sig->group_stop_count = 0;
if (task_set_jobctl_pending(current, signr | gstop))
sig->group_stop_count++;
t = current;
while_each_thread(current, t) {
/*
* Setting state to TASK_STOPPED for a group
* stop is always done with the siglock held,
* so this check has no races.
*/
if (!task_is_stopped(t) &&
task_set_jobctl_pending(t, signr | gstop)) {
sig->group_stop_count++;
ptrace: implement TRAP_NOTIFY and use it for group stop events Currently there's no way for ptracer to find out whether group stop finished other than polling with INTERRUPT - GETSIGINFO - CONT sequence. This patch implements group stop notification for ptracer using STOP traps. When group stop state of a seized tracee changes, JOBCTL_TRAP_NOTIFY is set, which schedules a STOP trap which is sticky - it isn't cleared by other traps and at least one STOP trap will happen eventually. STOP trap is synchronization point for event notification and the tracer can determine the current group stop state by looking at the signal number portion of exit code (si_status from waitid(2) or si_code from PTRACE_GETSIGINFO). Notifications are generated both on start and end of group stops but, because group stop participation always happens before STOP trap, this doesn't cause an extra trap while tracee is participating in group stop. The symmetry will be useful later. Note that this notification works iff tracee is not trapped. Currently there is no way to be notified of group stop state changes while tracee is trapped. This will be addressed by a later patch. An example program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) pause(); tracer = fork(); if (!tracer) { siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); repeat: waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (!si.si_code) { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); goto repeat; } printf("tracer: stopped=%d signo=%d\n", si.si_signo != SIGTRAP, si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, NULL); goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } In the above program, tracer keeps tracee running and gets notification of each group stop state changes. # ./test-notify tracer: stopped=0 signo=5 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:17 +00:00
if (likely(!(t->ptrace & PT_SEIZED)))
signal_wake_up(t, 0);
else
ptrace_trap_notify(t);
}
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
}
}
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
if (likely(!current->ptrace)) {
ptrace: Make do_signal_stop() use ptrace_stop() if the task is being ptraced A ptraced task would still stop at do_signal_stop() when it's stopping for stop signals and do_signal_stop() behaves the same whether the task is ptraced or not. However, in addition to stopping, ptrace_stop() also does ptrace specific stuff like calling architecture specific callbacks, so this behavior makes the code more fragile and difficult to understand. This patch makes do_signal_stop() test whether the task is ptraced and use ptrace_stop() if so. This renders tracehook_notify_jctl() rather pointless as the ptrace notification is now handled by ptrace_stop() regardless of the return value from the tracehook. It probably is a good idea to update it. This doesn't solve the whole problem as tasks already in stopped state would stay in the regular stop when ptrace attached. That part will be handled by the next patch. Oleg pointed out that this makes a userland-visible change. Before, SIGCONT would be able to wake up a task in group stop even if the task is ptraced if the tracer hasn't issued another ptrace command afterwards (as the next ptrace commands transitions the state into TASK_TRACED which ignores SIGCONT wakeups). With this and the next patch, SIGCONT may race with the transition into TASK_TRACED and is ignored if the tracee already entered TASK_TRACED. Another userland visible change of this and the next patch is that the ptracee's state would now be TASK_TRACED where it used to be TASK_STOPPED, which is visible via fs/proc. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
int notify = 0;
ptrace: Make do_signal_stop() use ptrace_stop() if the task is being ptraced A ptraced task would still stop at do_signal_stop() when it's stopping for stop signals and do_signal_stop() behaves the same whether the task is ptraced or not. However, in addition to stopping, ptrace_stop() also does ptrace specific stuff like calling architecture specific callbacks, so this behavior makes the code more fragile and difficult to understand. This patch makes do_signal_stop() test whether the task is ptraced and use ptrace_stop() if so. This renders tracehook_notify_jctl() rather pointless as the ptrace notification is now handled by ptrace_stop() regardless of the return value from the tracehook. It probably is a good idea to update it. This doesn't solve the whole problem as tasks already in stopped state would stay in the regular stop when ptrace attached. That part will be handled by the next patch. Oleg pointed out that this makes a userland-visible change. Before, SIGCONT would be able to wake up a task in group stop even if the task is ptraced if the tracer hasn't issued another ptrace command afterwards (as the next ptrace commands transitions the state into TASK_TRACED which ignores SIGCONT wakeups). With this and the next patch, SIGCONT may race with the transition into TASK_TRACED and is ignored if the tracee already entered TASK_TRACED. Another userland visible change of this and the next patch is that the ptracee's state would now be TASK_TRACED where it used to be TASK_STOPPED, which is visible via fs/proc. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
/*
* If there are no other threads in the group, or if there
* is a group stop in progress and we are the last to stop,
* report to the parent.
*/
if (task_participate_group_stop(current))
notify = CLD_STOPPED;
set_special_state(TASK_STOPPED);
ptrace: Make do_signal_stop() use ptrace_stop() if the task is being ptraced A ptraced task would still stop at do_signal_stop() when it's stopping for stop signals and do_signal_stop() behaves the same whether the task is ptraced or not. However, in addition to stopping, ptrace_stop() also does ptrace specific stuff like calling architecture specific callbacks, so this behavior makes the code more fragile and difficult to understand. This patch makes do_signal_stop() test whether the task is ptraced and use ptrace_stop() if so. This renders tracehook_notify_jctl() rather pointless as the ptrace notification is now handled by ptrace_stop() regardless of the return value from the tracehook. It probably is a good idea to update it. This doesn't solve the whole problem as tasks already in stopped state would stay in the regular stop when ptrace attached. That part will be handled by the next patch. Oleg pointed out that this makes a userland-visible change. Before, SIGCONT would be able to wake up a task in group stop even if the task is ptraced if the tracer hasn't issued another ptrace command afterwards (as the next ptrace commands transitions the state into TASK_TRACED which ignores SIGCONT wakeups). With this and the next patch, SIGCONT may race with the transition into TASK_TRACED and is ignored if the tracee already entered TASK_TRACED. Another userland visible change of this and the next patch is that the ptracee's state would now be TASK_TRACED where it used to be TASK_STOPPED, which is visible via fs/proc. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
spin_unlock_irq(&current->sighand->siglock);
/*
* Notify the parent of the group stop completion. Because
* we're not holding either the siglock or tasklist_lock
* here, ptracer may attach inbetween; however, this is for
* group stop and should always be delivered to the real
* parent of the group leader. The new ptracer will get
* its notification when this task transitions into
* TASK_TRACED.
*/
ptrace: Make do_signal_stop() use ptrace_stop() if the task is being ptraced A ptraced task would still stop at do_signal_stop() when it's stopping for stop signals and do_signal_stop() behaves the same whether the task is ptraced or not. However, in addition to stopping, ptrace_stop() also does ptrace specific stuff like calling architecture specific callbacks, so this behavior makes the code more fragile and difficult to understand. This patch makes do_signal_stop() test whether the task is ptraced and use ptrace_stop() if so. This renders tracehook_notify_jctl() rather pointless as the ptrace notification is now handled by ptrace_stop() regardless of the return value from the tracehook. It probably is a good idea to update it. This doesn't solve the whole problem as tasks already in stopped state would stay in the regular stop when ptrace attached. That part will be handled by the next patch. Oleg pointed out that this makes a userland-visible change. Before, SIGCONT would be able to wake up a task in group stop even if the task is ptraced if the tracer hasn't issued another ptrace command afterwards (as the next ptrace commands transitions the state into TASK_TRACED which ignores SIGCONT wakeups). With this and the next patch, SIGCONT may race with the transition into TASK_TRACED and is ignored if the tracee already entered TASK_TRACED. Another userland visible change of this and the next patch is that the ptracee's state would now be TASK_TRACED where it used to be TASK_STOPPED, which is visible via fs/proc. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
if (notify) {
read_lock(&tasklist_lock);
do_notify_parent_cldstop(current, false, notify);
ptrace: Make do_signal_stop() use ptrace_stop() if the task is being ptraced A ptraced task would still stop at do_signal_stop() when it's stopping for stop signals and do_signal_stop() behaves the same whether the task is ptraced or not. However, in addition to stopping, ptrace_stop() also does ptrace specific stuff like calling architecture specific callbacks, so this behavior makes the code more fragile and difficult to understand. This patch makes do_signal_stop() test whether the task is ptraced and use ptrace_stop() if so. This renders tracehook_notify_jctl() rather pointless as the ptrace notification is now handled by ptrace_stop() regardless of the return value from the tracehook. It probably is a good idea to update it. This doesn't solve the whole problem as tasks already in stopped state would stay in the regular stop when ptrace attached. That part will be handled by the next patch. Oleg pointed out that this makes a userland-visible change. Before, SIGCONT would be able to wake up a task in group stop even if the task is ptraced if the tracer hasn't issued another ptrace command afterwards (as the next ptrace commands transitions the state into TASK_TRACED which ignores SIGCONT wakeups). With this and the next patch, SIGCONT may race with the transition into TASK_TRACED and is ignored if the tracee already entered TASK_TRACED. Another userland visible change of this and the next patch is that the ptracee's state would now be TASK_TRACED where it used to be TASK_STOPPED, which is visible via fs/proc. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
read_unlock(&tasklist_lock);
}
/* Now we don't run again until woken by SIGCONT or SIGKILL */
freezable_schedule();
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
return true;
ptrace: Clean transitions between TASK_STOPPED and TRACED Currently, if the task is STOPPED on ptrace attach, it's left alone and the state is silently changed to TRACED on the next ptrace call. The behavior breaks the assumption that arch_ptrace_stop() is called before any task is poked by ptrace and is ugly in that a task manipulates the state of another task directly. With GROUP_STOP_PENDING, the transitions between TASK_STOPPED and TRACED can be made clean. The tracer can use the flag to tell the tracee to retry stop on attach and detach. On retry, the tracee will enter the desired state in the correct way. The lower 16bits of task->group_stop is used to remember the signal number which caused the last group stop. This is used while retrying for ptrace attach as the original group_exit_code could have been consumed with wait(2) by then. As the real parent may wait(2) and consume the group_exit_code anytime, the group_exit_code needs to be saved separately so that it can be used when switching from regular sleep to ptrace_stop(). This is recorded in the lower 16bits of task->group_stop. If a task is already stopped and there's no intervening SIGCONT, a ptrace request immediately following a successful PTRACE_ATTACH should always succeed even if the tracer doesn't wait(2) for attach completion; however, with this change, the tracee might still be TASK_RUNNING trying to enter TASK_TRACED which would cause the following request to fail with -ESRCH. This intermediate state is hidden from the ptracer by setting GROUP_STOP_TRAPPING on attach and making ptrace_check_attach() wait for it to clear on its signal->wait_chldexit. Completing the transition or getting killed clears TRAPPING and wakes up the tracer. Note that the STOPPED -> RUNNING -> TRACED transition is still visible to other threads which are in the same group as the ptracer and the reverse transition is visible to all. Please read the comments for details. Oleg: * Spotted a race condition where a task may retry group stop without proper bookkeeping. Fixed by redoing bookkeeping on retry. * Spotted that the transition is visible to userland in several different ways. Most are fixed with GROUP_STOP_TRAPPING. Unhandled corner case is documented. * Pointed out not setting GROUP_STOP_SIGMASK on an already stopped task would result in more consistent behavior. * Pointed out that calling ptrace_stop() from do_signal_stop() in TASK_STOPPED can race with group stop start logic and then confuse the TRAPPING wait in ptrace_check_attach(). ptrace_stop() is now called with TASK_RUNNING. * Suggested using signal->wait_chldexit instead of bit wait. * Spotted a race condition between TRACED transition and clearing of TRAPPING. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
2011-03-23 09:37:00 +00:00
} else {
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
/*
* While ptraced, group stop is handled by STOP trap.
* Schedule it and let the caller deal with it.
*/
task_set_jobctl_pending(current, JOBCTL_TRAP_STOP);
return false;
}
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
}
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
/**
* do_jobctl_trap - take care of ptrace jobctl traps
*
ptrace: implement PTRACE_SEIZE PTRACE_ATTACH implicitly issues SIGSTOP on attach which has side effects on tracee signal and job control states. This patch implements a new ptrace request PTRACE_SEIZE which attaches a tracee without trapping it or affecting its signal and job control states. The usage is the same with PTRACE_ATTACH but it takes PTRACE_SEIZE_* flags in @data. Currently, the only defined flag is PTRACE_SEIZE_DEVEL which is a temporary flag to enable PTRACE_SEIZE. PTRACE_SEIZE will change ptrace behaviors outside of attach itself. The changes will be implemented gradually and the DEVEL flag is to prevent programs which expect full SEIZE behavior from using it before all the behavior modifications are complete while allowing unit testing. The flag will be removed once SEIZE behaviors are completely implemented. * PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After attaching tracee continues to run unless a trap condition occurs. * PTRACE_SEIZE doesn't affect signal or group stop state. * If PTRACE_SEIZE'd, group stop uses PTRACE_EVENT_STOP trap which uses exit_code of (signr | PTRACE_EVENT_STOP << 8) where signr is one of the stopping signals if group stop is in effect or SIGTRAP otherwise, and returns usual trap siginfo on PTRACE_GETSIGINFO instead of NULL. Seizing sets PT_SEIZED in ->ptrace of the tracee. This flag will be used to determine whether new SEIZE behaviors should be enabled. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static const struct timespec ts1s = { .tv_sec = 1 }; static const struct timespec ts3s = { .tv_sec = 3 }; int main(int argc, char **argv) { pid_t tracee; tracee = fork(); if (tracee == 0) { nanosleep(&ts100ms, NULL); while (1) { printf("tracee: alive\n"); nanosleep(&ts1s, NULL); } } if (argc > 1) kill(tracee, SIGSTOP); nanosleep(&ts100ms, NULL); ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); if (argc > 1) { waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, NULL); } nanosleep(&ts3s, NULL); printf("tracer: exiting\n"); return 0; } When the above program is called w/o argument, tracee is seized while running and remains running. When tracer exits, tracee continues to run and print out messages. # ./test-seize-simple tracee: alive tracee: alive tracee: alive tracer: exiting tracee: alive tracee: alive When called with an argument, tracee is seized from stopped state and continued, and returns to stopped state when tracer exits. # ./test-seize tracee: alive tracee: alive tracee: alive tracer: exiting # ps -el|grep test-seize 1 T 0 4720 1 0 80 0 - 941 signal ttyS0 00:00:00 test-seize -v2: SEIZE doesn't schedule TRAP_STOP and leaves tracee running as Jan suggested. -v3: PTRACE_EVENT_STOP traps now report group stop state by signr. If group stop is in effect the stop signal number is returned as part of exit_code; otherwise, SIGTRAP. This was suggested by Denys and Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:15 +00:00
* When PT_SEIZED, it's used for both group stop and explicit
* SEIZE/INTERRUPT traps. Both generate PTRACE_EVENT_STOP trap with
* accompanying siginfo. If stopped, lower eight bits of exit_code contain
* the stop signal; otherwise, %SIGTRAP.
*
* When !PT_SEIZED, it's used only for group stop trap with stop signal
* number as exit_code and no siginfo.
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
*
* CONTEXT:
* Must be called with @current->sighand->siglock held, which may be
* released and re-acquired before returning with intervening sleep.
*/
static void do_jobctl_trap(void)
{
ptrace: implement PTRACE_SEIZE PTRACE_ATTACH implicitly issues SIGSTOP on attach which has side effects on tracee signal and job control states. This patch implements a new ptrace request PTRACE_SEIZE which attaches a tracee without trapping it or affecting its signal and job control states. The usage is the same with PTRACE_ATTACH but it takes PTRACE_SEIZE_* flags in @data. Currently, the only defined flag is PTRACE_SEIZE_DEVEL which is a temporary flag to enable PTRACE_SEIZE. PTRACE_SEIZE will change ptrace behaviors outside of attach itself. The changes will be implemented gradually and the DEVEL flag is to prevent programs which expect full SEIZE behavior from using it before all the behavior modifications are complete while allowing unit testing. The flag will be removed once SEIZE behaviors are completely implemented. * PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After attaching tracee continues to run unless a trap condition occurs. * PTRACE_SEIZE doesn't affect signal or group stop state. * If PTRACE_SEIZE'd, group stop uses PTRACE_EVENT_STOP trap which uses exit_code of (signr | PTRACE_EVENT_STOP << 8) where signr is one of the stopping signals if group stop is in effect or SIGTRAP otherwise, and returns usual trap siginfo on PTRACE_GETSIGINFO instead of NULL. Seizing sets PT_SEIZED in ->ptrace of the tracee. This flag will be used to determine whether new SEIZE behaviors should be enabled. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static const struct timespec ts1s = { .tv_sec = 1 }; static const struct timespec ts3s = { .tv_sec = 3 }; int main(int argc, char **argv) { pid_t tracee; tracee = fork(); if (tracee == 0) { nanosleep(&ts100ms, NULL); while (1) { printf("tracee: alive\n"); nanosleep(&ts1s, NULL); } } if (argc > 1) kill(tracee, SIGSTOP); nanosleep(&ts100ms, NULL); ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); if (argc > 1) { waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, NULL); } nanosleep(&ts3s, NULL); printf("tracer: exiting\n"); return 0; } When the above program is called w/o argument, tracee is seized while running and remains running. When tracer exits, tracee continues to run and print out messages. # ./test-seize-simple tracee: alive tracee: alive tracee: alive tracer: exiting tracee: alive tracee: alive When called with an argument, tracee is seized from stopped state and continued, and returns to stopped state when tracer exits. # ./test-seize tracee: alive tracee: alive tracee: alive tracer: exiting # ps -el|grep test-seize 1 T 0 4720 1 0 80 0 - 941 signal ttyS0 00:00:00 test-seize -v2: SEIZE doesn't schedule TRAP_STOP and leaves tracee running as Jan suggested. -v3: PTRACE_EVENT_STOP traps now report group stop state by signr. If group stop is in effect the stop signal number is returned as part of exit_code; otherwise, SIGTRAP. This was suggested by Denys and Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:15 +00:00
struct signal_struct *signal = current->signal;
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
int signr = current->jobctl & JOBCTL_STOP_SIGMASK;
ptrace: implement PTRACE_SEIZE PTRACE_ATTACH implicitly issues SIGSTOP on attach which has side effects on tracee signal and job control states. This patch implements a new ptrace request PTRACE_SEIZE which attaches a tracee without trapping it or affecting its signal and job control states. The usage is the same with PTRACE_ATTACH but it takes PTRACE_SEIZE_* flags in @data. Currently, the only defined flag is PTRACE_SEIZE_DEVEL which is a temporary flag to enable PTRACE_SEIZE. PTRACE_SEIZE will change ptrace behaviors outside of attach itself. The changes will be implemented gradually and the DEVEL flag is to prevent programs which expect full SEIZE behavior from using it before all the behavior modifications are complete while allowing unit testing. The flag will be removed once SEIZE behaviors are completely implemented. * PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After attaching tracee continues to run unless a trap condition occurs. * PTRACE_SEIZE doesn't affect signal or group stop state. * If PTRACE_SEIZE'd, group stop uses PTRACE_EVENT_STOP trap which uses exit_code of (signr | PTRACE_EVENT_STOP << 8) where signr is one of the stopping signals if group stop is in effect or SIGTRAP otherwise, and returns usual trap siginfo on PTRACE_GETSIGINFO instead of NULL. Seizing sets PT_SEIZED in ->ptrace of the tracee. This flag will be used to determine whether new SEIZE behaviors should be enabled. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static const struct timespec ts1s = { .tv_sec = 1 }; static const struct timespec ts3s = { .tv_sec = 3 }; int main(int argc, char **argv) { pid_t tracee; tracee = fork(); if (tracee == 0) { nanosleep(&ts100ms, NULL); while (1) { printf("tracee: alive\n"); nanosleep(&ts1s, NULL); } } if (argc > 1) kill(tracee, SIGSTOP); nanosleep(&ts100ms, NULL); ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); if (argc > 1) { waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, NULL); } nanosleep(&ts3s, NULL); printf("tracer: exiting\n"); return 0; } When the above program is called w/o argument, tracee is seized while running and remains running. When tracer exits, tracee continues to run and print out messages. # ./test-seize-simple tracee: alive tracee: alive tracee: alive tracer: exiting tracee: alive tracee: alive When called with an argument, tracee is seized from stopped state and continued, and returns to stopped state when tracer exits. # ./test-seize tracee: alive tracee: alive tracee: alive tracer: exiting # ps -el|grep test-seize 1 T 0 4720 1 0 80 0 - 941 signal ttyS0 00:00:00 test-seize -v2: SEIZE doesn't schedule TRAP_STOP and leaves tracee running as Jan suggested. -v3: PTRACE_EVENT_STOP traps now report group stop state by signr. If group stop is in effect the stop signal number is returned as part of exit_code; otherwise, SIGTRAP. This was suggested by Denys and Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:15 +00:00
if (current->ptrace & PT_SEIZED) {
if (!signal->group_stop_count &&
!(signal->flags & SIGNAL_STOP_STOPPED))
signr = SIGTRAP;
WARN_ON_ONCE(!signr);
ptrace_do_notify(signr, signr | (PTRACE_EVENT_STOP << 8),
CLD_STOPPED);
} else {
WARN_ON_ONCE(!signr);
ptrace_stop(signr, CLD_STOPPED, 0, NULL);
current->exit_code = 0;
}
}
static int ptrace_signal(int signr, siginfo_t *info)
{
ptrace: fix ptrace_signal() && STOP_DEQUEUED interaction Simple test-case, int main(void) { int pid, status; pid = fork(); if (!pid) { pause(); assert(0); return 0x23; } assert(ptrace(PTRACE_ATTACH, pid, 0,0) == 0); assert(wait(&status) == pid); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP); kill(pid, SIGCONT); // <--- also clears STOP_DEQUEUD assert(ptrace(PTRACE_CONT, pid, 0,0) == 0); assert(wait(&status) == pid); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGCONT); assert(ptrace(PTRACE_CONT, pid, 0, SIGSTOP) == 0); assert(wait(&status) == pid); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP); kill(pid, SIGKILL); return 0; } Without the patch it hangs. After the patch SIGSTOP "injected" by the tracer is not ignored and stops the tracee. Note also that if this test-case uses, say, SIGWINCH instead of SIGCONT, everything works without the patch. This can't be right, and this is confusing. The problem is that SIGSTOP (or any other sig_kernel_stop() signal) has no effect without JOBCTL_STOP_DEQUEUED. This means it is simply ignored after PTRACE_CONT unless JOBCTL_STOP_DEQUEUED was set "by accident", say it wasn't cleared after initial SIGSTOP sent by PTRACE_ATTACH. At first glance we could change ptrace_signal() to add STOP_DEQUEUED after return from ptrace_stop(), but this is not right in case when the tracer does not change the reported SIGSTOP and SIGCONT comes in between. This is even more wrong with PT_SEIZED, SIGCONT adds JOBCTL_TRAP_NOTIFY which will be "lost" during the TRAP_STOP | TRAP_NOTIFY report. So lets add STOP_DEQUEUED _before_ we report the signal. It has no effect unless sig_kernel_stop() == T after the tracer resumes us, and in the latter case the pending STOP_DEQUEUED means no SIGCONT in between, we should stop. Note also that if SIGCONT was sent, PT_SEIZED tracee will correctly report PTRACE_EVENT_STOP/SIGTRAP and thus the tracer can notice the fact SIGSTOP was cancelled. Also, move the current->ptrace check from ptrace_signal() to its caller, get_signal_to_deliver(), this looks more natural. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Tejun Heo <tj@kernel.org>
2011-07-21 15:06:53 +00:00
/*
* We do not check sig_kernel_stop(signr) but set this marker
* unconditionally because we do not know whether debugger will
* change signr. This flag has no meaning unless we are going
* to stop after return from ptrace_stop(). In this case it will
* be checked in do_signal_stop(), we should only stop if it was
* not cleared by SIGCONT while we were sleeping. See also the
* comment in dequeue_signal().
*/
current->jobctl |= JOBCTL_STOP_DEQUEUED;
ptrace_stop(signr, CLD_TRAPPED, 0, info);
/* We're back. Did the debugger cancel the sig? */
signr = current->exit_code;
if (signr == 0)
return signr;
current->exit_code = 0;
/*
* Update the siginfo structure if the signal has
* changed. If the debugger wanted something
* specific in the siginfo structure then it should
* have updated *info via PTRACE_SETSIGINFO.
*/
if (signr != info->si_signo) {
clear_siginfo(info);
info->si_signo = signr;
info->si_errno = 0;
info->si_code = SI_USER;
user namespace: make signal.c respect user namespaces ipc/mqueue.c: for __SI_MESQ, convert the uid being sent to recipient's user namespace. (new, thanks Oleg) __send_signal: convert current's uid to the recipient's user namespace for any siginfo which is not SI_FROMKERNEL (patch from Oleg, thanks again :) do_notify_parent and do_notify_parent_cldstop: map task's uid to parent's user namespace ptrace_signal maps parent's uid into current's user namespace before including in signal to current. IIUC Oleg has argued that this shouldn't matter as the debugger will play with it, but it seems like not converting the value currently being set is misleading. Changelog: Sep 20: Inspired by Oleg's suggestion, define map_cred_ns() helper to simplify callers and help make clear what we are translating (which uid into which namespace). Passing the target task would make callers even easier to read, but we pass in user_ns because current_user_ns() != task_cred_xxx(current, user_ns). Sep 20: As recommended by Oleg, also put task_pid_vnr() under rcu_read_lock in ptrace_signal(). Sep 23: In send_signal(), detect when (user) signal is coming from an ancestor or unrelated user namespace. Pass that on to __send_signal, which sets si_uid to 0 or overflowuid if needed. Oct 12: Base on Oleg's fixup_uid() patch. On top of that, handle all SI_FROMKERNEL cases at callers, because we can't assume sender is current in those cases. Nov 10: (mhelsley) rename fixup_uid to more meaningful usern_fixup_signal_uid Nov 10: (akpm) make the !CONFIG_USER_NS case clearer Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Serge Hallyn <serge.hallyn@canonical.com> Subject: __send_signal: pass q->info, not info, to userns_fixup_signal_uid (v2) Eric Biederman pointed out that passing info is a bug and could lead to a NULL pointer deref to boot. A collection of signal, securebits, filecaps, cap_bounds, and a few other ltp tests passed with this kernel. Changelog: Nov 18: previous patch missed a leading '&' Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Dan Carpenter <dan.carpenter@oracle.com> Subject: ipc/mqueue: lock() => unlock() typo There was a double lock typo introduced in b085f4bd6b21 "user namespace: make signal.c respect user namespaces" Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Serge Hallyn <serge@hallyn.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-10 23:11:37 +00:00
rcu_read_lock();
info->si_pid = task_pid_vnr(current->parent);
info->si_uid = from_kuid_munged(current_user_ns(),
task_uid(current->parent));
user namespace: make signal.c respect user namespaces ipc/mqueue.c: for __SI_MESQ, convert the uid being sent to recipient's user namespace. (new, thanks Oleg) __send_signal: convert current's uid to the recipient's user namespace for any siginfo which is not SI_FROMKERNEL (patch from Oleg, thanks again :) do_notify_parent and do_notify_parent_cldstop: map task's uid to parent's user namespace ptrace_signal maps parent's uid into current's user namespace before including in signal to current. IIUC Oleg has argued that this shouldn't matter as the debugger will play with it, but it seems like not converting the value currently being set is misleading. Changelog: Sep 20: Inspired by Oleg's suggestion, define map_cred_ns() helper to simplify callers and help make clear what we are translating (which uid into which namespace). Passing the target task would make callers even easier to read, but we pass in user_ns because current_user_ns() != task_cred_xxx(current, user_ns). Sep 20: As recommended by Oleg, also put task_pid_vnr() under rcu_read_lock in ptrace_signal(). Sep 23: In send_signal(), detect when (user) signal is coming from an ancestor or unrelated user namespace. Pass that on to __send_signal, which sets si_uid to 0 or overflowuid if needed. Oct 12: Base on Oleg's fixup_uid() patch. On top of that, handle all SI_FROMKERNEL cases at callers, because we can't assume sender is current in those cases. Nov 10: (mhelsley) rename fixup_uid to more meaningful usern_fixup_signal_uid Nov 10: (akpm) make the !CONFIG_USER_NS case clearer Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Serge Hallyn <serge.hallyn@canonical.com> Subject: __send_signal: pass q->info, not info, to userns_fixup_signal_uid (v2) Eric Biederman pointed out that passing info is a bug and could lead to a NULL pointer deref to boot. A collection of signal, securebits, filecaps, cap_bounds, and a few other ltp tests passed with this kernel. Changelog: Nov 18: previous patch missed a leading '&' Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> From: Dan Carpenter <dan.carpenter@oracle.com> Subject: ipc/mqueue: lock() => unlock() typo There was a double lock typo introduced in b085f4bd6b21 "user namespace: make signal.c respect user namespaces" Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Serge Hallyn <serge@hallyn.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-10 23:11:37 +00:00
rcu_read_unlock();
}
/* If the (new) signal is now blocked, requeue it. */
if (sigismember(&current->blocked, signr)) {
specific_send_sig_info(signr, info, current);
signr = 0;
}
return signr;
}
int get_signal(struct ksignal *ksig)
{
struct sighand_struct *sighand = current->sighand;
struct signal_struct *signal = current->signal;
int signr;
if (unlikely(current->task_works))
task_work_run();
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
if (unlikely(uprobe_deny_signal()))
return 0;
/*
* Do this once, we can't return to user-mode if freezing() == T.
* do_signal_stop() and ptrace_stop() do freezable_schedule() and
* thus do not need another check after return.
*/
try_to_freeze();
relock:
spin_lock_irq(&sighand->siglock);
/*
* Every stopped thread goes here after wakeup. Check to see if
* we should notify the parent, prepare_signal(SIGCONT) encodes
* the CLD_ si_code into SIGNAL_CLD_MASK bits.
*/
if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
int why;
if (signal->flags & SIGNAL_CLD_CONTINUED)
why = CLD_CONTINUED;
else
why = CLD_STOPPED;
signal->flags &= ~SIGNAL_CLD_MASK;
signals: re-assign CLD_CONTINUED notification from the sender to reciever Based on discussion with Jiri and Roland. In short: currently handle_stop_signal(SIGCONT, p) sends the notification to p->parent, with this patch p itself notifies its parent when it becomes running. handle_stop_signal(SIGCONT) has to drop ->siglock temporary in order to notify the parent with do_notify_parent_cldstop(). This leads to multiple problems: - as Jiri Kosina pointed out, the stopped task can resume without actually seeing SIGCONT which may have a handler. - we race with another sig_kernel_stop() signal which may come in that window. - we race with sig_fatal() signals which may set SIGNAL_GROUP_EXIT in that window. - we can't avoid taking tasklist_lock() while sending SIGCONT. With this patch handle_stop_signal() just sets the new SIGNAL_CLD_CONTINUED flag in p->signal->flags and returns. The notification is sent by the first task which returns from finish_stop() (there should be at least one) or any other signalled thread from get_signal_to_deliver(). This is a user-visible change. Say, currently kill(SIGCONT, stopped_child) can't return without seeing SIGCHLD, with this patch SIGCHLD can be delayed unpredictably. Another difference is that if the child is ptraced by another process, CLD_CONTINUED may be delivered to ->real_parent after ptrace_detach() while currently it always goes to the tracer which doesn't actually need this notification. Hopefully not a problem. The patch asks for the futher obvious cleanups, I'll send them separately. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Cc: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 07:52:44 +00:00
spin_unlock_irq(&sighand->siglock);
job control: Notify the real parent of job control events regardless of ptrace With recent changes, job control and ptrace stopped states are properly separated and accessible to the real parent and the ptracer respectively; however, notifications of job control stopped/continued events to the real parent while ptraced are still missing. A ptracee participates in group stop in ptrace_stop() but the completion isn't notified. If participation results in completion of group stop, notify the real parent of the event. The ptrace and group stops are separate and can be handled as such. However, when the real parent and the ptracer are in the same thread group, only the ptrace stop event is visible through wait(2) and the duplicate notifications are different from the current behavior and are confusing. Suppress group stop notification in such cases. The continued state is shared between the real parent and the ptracer but is only meaningful to the real parent. Always notify the real parent and notify the ptracer too for backward compatibility. Similar to stop notification, if the real parent is the ptracer, suppress a duplicate notification. Test case follows. #include <stdio.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <sys/types.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { const struct timespec ts100ms = { .tv_nsec = 100000000 }; pid_t tracee, tracer; siginfo_t si; int i; tracee = fork(); if (tracee == 0) { while (1) { printf("tracee: SIGSTOP\n"); raise(SIGSTOP); nanosleep(&ts100ms, NULL); printf("tracee: SIGCONT\n"); raise(SIGCONT); nanosleep(&ts100ms, NULL); } } waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG | WNOWAIT); tracer = fork(); if (tracer == 0) { nanosleep(&ts100ms, NULL); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); for (i = 0; i < 11; i++) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED); if (si.si_pid && si.si_code == CLD_TRAPPED) ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); } printf("tracer: EXITING\n"); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WCONTINUED | WEXITED); if (si.si_pid) printf("mommy : WAIT status=%02d code=%02d\n", si.si_status, si.si_code); } return 0; } Before this patch, while ptraced, the real parent doesn't get notifications for job control events, so although it can access those events, the later waitid(2) call never wakes up. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C After this patch, it works as expected. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C -v2: Oleg pointed out that * Group stop notification to the real parent should also happen when ptracer detach races with ptrace_stop(). * real_parent_is_ptracer() should be testing thread group equality not the task itself as wait(2) and stop/cont notifications are normally thread-group wide. Both issues are fixed accordingly. -v3: real_parent_is_ptracer() updated to test child->real_parent instead of child->group_leader->real_parent per Oleg's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
/*
* Notify the parent that we're continuing. This event is
* always per-process and doesn't make whole lot of sense
* for ptracers, who shouldn't consume the state via
* wait(2) either, but, for backward compatibility, notify
* the ptracer of the group leader too unless it's gonna be
* a duplicate.
*/
read_lock(&tasklist_lock);
job control: Notify the real parent of job control events regardless of ptrace With recent changes, job control and ptrace stopped states are properly separated and accessible to the real parent and the ptracer respectively; however, notifications of job control stopped/continued events to the real parent while ptraced are still missing. A ptracee participates in group stop in ptrace_stop() but the completion isn't notified. If participation results in completion of group stop, notify the real parent of the event. The ptrace and group stops are separate and can be handled as such. However, when the real parent and the ptracer are in the same thread group, only the ptrace stop event is visible through wait(2) and the duplicate notifications are different from the current behavior and are confusing. Suppress group stop notification in such cases. The continued state is shared between the real parent and the ptracer but is only meaningful to the real parent. Always notify the real parent and notify the ptracer too for backward compatibility. Similar to stop notification, if the real parent is the ptracer, suppress a duplicate notification. Test case follows. #include <stdio.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <sys/types.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { const struct timespec ts100ms = { .tv_nsec = 100000000 }; pid_t tracee, tracer; siginfo_t si; int i; tracee = fork(); if (tracee == 0) { while (1) { printf("tracee: SIGSTOP\n"); raise(SIGSTOP); nanosleep(&ts100ms, NULL); printf("tracee: SIGCONT\n"); raise(SIGCONT); nanosleep(&ts100ms, NULL); } } waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG | WNOWAIT); tracer = fork(); if (tracer == 0) { nanosleep(&ts100ms, NULL); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); for (i = 0; i < 11; i++) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED); if (si.si_pid && si.si_code == CLD_TRAPPED) ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); } printf("tracer: EXITING\n"); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WCONTINUED | WEXITED); if (si.si_pid) printf("mommy : WAIT status=%02d code=%02d\n", si.si_status, si.si_code); } return 0; } Before this patch, while ptraced, the real parent doesn't get notifications for job control events, so although it can access those events, the later waitid(2) call never wakes up. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C After this patch, it works as expected. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C -v2: Oleg pointed out that * Group stop notification to the real parent should also happen when ptracer detach races with ptrace_stop(). * real_parent_is_ptracer() should be testing thread group equality not the task itself as wait(2) and stop/cont notifications are normally thread-group wide. Both issues are fixed accordingly. -v3: real_parent_is_ptracer() updated to test child->real_parent instead of child->group_leader->real_parent per Oleg's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
do_notify_parent_cldstop(current, false, why);
if (ptrace_reparented(current->group_leader))
do_notify_parent_cldstop(current->group_leader,
true, why);
read_unlock(&tasklist_lock);
job control: Notify the real parent of job control events regardless of ptrace With recent changes, job control and ptrace stopped states are properly separated and accessible to the real parent and the ptracer respectively; however, notifications of job control stopped/continued events to the real parent while ptraced are still missing. A ptracee participates in group stop in ptrace_stop() but the completion isn't notified. If participation results in completion of group stop, notify the real parent of the event. The ptrace and group stops are separate and can be handled as such. However, when the real parent and the ptracer are in the same thread group, only the ptrace stop event is visible through wait(2) and the duplicate notifications are different from the current behavior and are confusing. Suppress group stop notification in such cases. The continued state is shared between the real parent and the ptracer but is only meaningful to the real parent. Always notify the real parent and notify the ptracer too for backward compatibility. Similar to stop notification, if the real parent is the ptracer, suppress a duplicate notification. Test case follows. #include <stdio.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <sys/types.h> #include <sys/ptrace.h> #include <sys/wait.h> int main(void) { const struct timespec ts100ms = { .tv_nsec = 100000000 }; pid_t tracee, tracer; siginfo_t si; int i; tracee = fork(); if (tracee == 0) { while (1) { printf("tracee: SIGSTOP\n"); raise(SIGSTOP); nanosleep(&ts100ms, NULL); printf("tracee: SIGCONT\n"); raise(SIGCONT); nanosleep(&ts100ms, NULL); } } waitid(P_PID, tracee, &si, WSTOPPED | WNOHANG | WNOWAIT); tracer = fork(); if (tracer == 0) { nanosleep(&ts100ms, NULL); ptrace(PTRACE_ATTACH, tracee, NULL, NULL); for (i = 0; i < 11; i++) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED); if (si.si_pid && si.si_code == CLD_TRAPPED) ptrace(PTRACE_CONT, tracee, NULL, (void *)(long)si.si_status); } printf("tracer: EXITING\n"); return 0; } while (1) { si.si_pid = 0; waitid(P_PID, tracee, &si, WSTOPPED | WCONTINUED | WEXITED); if (si.si_pid) printf("mommy : WAIT status=%02d code=%02d\n", si.si_status, si.si_code); } return 0; } Before this patch, while ptraced, the real parent doesn't get notifications for job control events, so although it can access those events, the later waitid(2) call never wakes up. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracee: SIGCONT tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C After this patch, it works as expected. tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP mommy : WAIT status=19 code=05 tracee: SIGCONT mommy : WAIT status=18 code=06 tracee: SIGSTOP tracer: EXITING mommy : WAIT status=19 code=05 ^C -v2: Oleg pointed out that * Group stop notification to the real parent should also happen when ptracer detach races with ptrace_stop(). * real_parent_is_ptracer() should be testing thread group equality not the task itself as wait(2) and stop/cont notifications are normally thread-group wide. Both issues are fixed accordingly. -v3: real_parent_is_ptracer() updated to test child->real_parent instead of child->group_leader->real_parent per Oleg's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2011-03-23 09:37:01 +00:00
signals: re-assign CLD_CONTINUED notification from the sender to reciever Based on discussion with Jiri and Roland. In short: currently handle_stop_signal(SIGCONT, p) sends the notification to p->parent, with this patch p itself notifies its parent when it becomes running. handle_stop_signal(SIGCONT) has to drop ->siglock temporary in order to notify the parent with do_notify_parent_cldstop(). This leads to multiple problems: - as Jiri Kosina pointed out, the stopped task can resume without actually seeing SIGCONT which may have a handler. - we race with another sig_kernel_stop() signal which may come in that window. - we race with sig_fatal() signals which may set SIGNAL_GROUP_EXIT in that window. - we can't avoid taking tasklist_lock() while sending SIGCONT. With this patch handle_stop_signal() just sets the new SIGNAL_CLD_CONTINUED flag in p->signal->flags and returns. The notification is sent by the first task which returns from finish_stop() (there should be at least one) or any other signalled thread from get_signal_to_deliver(). This is a user-visible change. Say, currently kill(SIGCONT, stopped_child) can't return without seeing SIGCHLD, with this patch SIGCHLD can be delayed unpredictably. Another difference is that if the child is ptraced by another process, CLD_CONTINUED may be delivered to ->real_parent after ptrace_detach() while currently it always goes to the tracer which doesn't actually need this notification. Hopefully not a problem. The patch asks for the futher obvious cleanups, I'll send them separately. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Cc: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 07:52:44 +00:00
goto relock;
}
for (;;) {
struct k_sigaction *ka;
if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) &&
do_signal_stop(0))
goto relock;
job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap do_signal_stop() implemented both normal group stop and trap for group stop while ptraced. This approach has been enough but scheduled changes require trap mechanism which can be used in more generic manner and using group stop trap for generic trap site simplifies both userland visible interface and implementation. This patch adds a new jobctl flag - JOBCTL_TRAP_STOP. When set, it triggers a trap site, which behaves like group stop trap, in get_signal_to_deliver() after checking for pending signals. While ptraced, do_signal_stop() doesn't stop itself. It initiates group stop if requested and schedules JOBCTL_TRAP_STOP and returns. The caller - get_signal_to_deliver() - is responsible for checking whether TRAP_STOP is pending afterwards and handling it. ptrace_attach() is updated to use JOBCTL_TRAP_STOP instead of JOBCTL_STOP_PENDING and __ptrace_unlink() to clear all pending trap bits and TRAPPING so that TRAP_STOP and future trap bits don't linger after detach. While at it, add proper function comment to do_signal_stop() and make it return bool. -v2: __ptrace_unlink() updated to clear JOBCTL_TRAP_MASK and TRAPPING instead of JOBCTL_PENDING_MASK. This avoids accidentally clearing JOBCTL_STOP_CONSUME. Spotted by Oleg. -v3: do_signal_stop() updated to return %false without dropping siglock while ptraced and TRAP_STOP check moved inside for(;;) loop after group stop participation. This avoids unnecessary relocking and also will help avoiding unnecessary traps by consuming group stop before handling pending traps. -v4: Jobctl trap handling moved into a separate function - do_jobctl_trap(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
2011-06-14 09:20:14 +00:00
if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) {
do_jobctl_trap();
spin_unlock_irq(&sighand->siglock);
goto relock;
}
signr = dequeue_signal(current, &current->blocked, &ksig->info);
if (!signr)
break; /* will return 0 */
ptrace: fix ptrace_signal() && STOP_DEQUEUED interaction Simple test-case, int main(void) { int pid, status; pid = fork(); if (!pid) { pause(); assert(0); return 0x23; } assert(ptrace(PTRACE_ATTACH, pid, 0,0) == 0); assert(wait(&status) == pid); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP); kill(pid, SIGCONT); // <--- also clears STOP_DEQUEUD assert(ptrace(PTRACE_CONT, pid, 0,0) == 0); assert(wait(&status) == pid); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGCONT); assert(ptrace(PTRACE_CONT, pid, 0, SIGSTOP) == 0); assert(wait(&status) == pid); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP); kill(pid, SIGKILL); return 0; } Without the patch it hangs. After the patch SIGSTOP "injected" by the tracer is not ignored and stops the tracee. Note also that if this test-case uses, say, SIGWINCH instead of SIGCONT, everything works without the patch. This can't be right, and this is confusing. The problem is that SIGSTOP (or any other sig_kernel_stop() signal) has no effect without JOBCTL_STOP_DEQUEUED. This means it is simply ignored after PTRACE_CONT unless JOBCTL_STOP_DEQUEUED was set "by accident", say it wasn't cleared after initial SIGSTOP sent by PTRACE_ATTACH. At first glance we could change ptrace_signal() to add STOP_DEQUEUED after return from ptrace_stop(), but this is not right in case when the tracer does not change the reported SIGSTOP and SIGCONT comes in between. This is even more wrong with PT_SEIZED, SIGCONT adds JOBCTL_TRAP_NOTIFY which will be "lost" during the TRAP_STOP | TRAP_NOTIFY report. So lets add STOP_DEQUEUED _before_ we report the signal. It has no effect unless sig_kernel_stop() == T after the tracer resumes us, and in the latter case the pending STOP_DEQUEUED means no SIGCONT in between, we should stop. Note also that if SIGCONT was sent, PT_SEIZED tracee will correctly report PTRACE_EVENT_STOP/SIGTRAP and thus the tracer can notice the fact SIGSTOP was cancelled. Also, move the current->ptrace check from ptrace_signal() to its caller, get_signal_to_deliver(), this looks more natural. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Tejun Heo <tj@kernel.org>
2011-07-21 15:06:53 +00:00
if (unlikely(current->ptrace) && signr != SIGKILL) {
signr = ptrace_signal(signr, &ksig->info);
if (!signr)
continue;
}
ka = &sighand->action[signr-1];
/* Trace actually delivered signals. */
trace_signal_deliver(signr, &ksig->info, ka);
if (ka->sa.sa_handler == SIG_IGN) /* Do nothing. */
continue;
if (ka->sa.sa_handler != SIG_DFL) {
/* Run the handler. */
ksig->ka = *ka;
if (ka->sa.sa_flags & SA_ONESHOT)
ka->sa.sa_handler = SIG_DFL;
break; /* will return non-zero "signr" value */
}
/*
* Now we are doing the default action for this signal.
*/
if (sig_kernel_ignore(signr)) /* Default is nothing. */
continue;
/*
* Global init gets no signals it doesn't want.
signals: protect cinit from blocked fatal signals Normally SIG_DFL signals to global and container-init are dropped early. But if a signal is blocked when it is posted, we cannot drop the signal since the receiver may install a handler before unblocking the signal. Once this signal is queued however, the receiver container-init has no way of knowing if the signal was sent from an ancestor or descendant namespace. This patch ensures that contianer-init drops all SIG_DFL signals in get_signal_to_deliver() except SIGKILL/SIGSTOP. If SIGSTOP/SIGKILL originate from a descendant of container-init they are never queued (i.e dropped in sig_ignored() in an earler patch). If SIGSTOP/SIGKILL originate from parent namespace, the signal is queued and container-init processes the signal. IOW, if get_signal_to_deliver() sees a sig_kernel_only() signal for global or container-init, the signal must have been generated internally or must have come from an ancestor ns and we process the signal. Further, the signal_group_exit() check was needed to cover the case of a multi-threaded init sending SIGKILL to other threads when doing an exit() or exec(). But since the new sig_kernel_only() check covers the SIGKILL, the signal_group_exit() check is no longer needed and can be removed. Finally, now that we have all pieces in place, set SIGNAL_UNKILLABLE for container-inits. Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Daniel Lezcano <daniel.lezcano@free.fr> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-02 23:58:08 +00:00
* Container-init gets no signals it doesn't want from same
* container.
*
* Note that if global/container-init sees a sig_kernel_only()
* signal here, the signal must have been generated internally
* or must have come from an ancestor namespace. In either
* case, the signal cannot be dropped.
*/
if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
signals: protect cinit from blocked fatal signals Normally SIG_DFL signals to global and container-init are dropped early. But if a signal is blocked when it is posted, we cannot drop the signal since the receiver may install a handler before unblocking the signal. Once this signal is queued however, the receiver container-init has no way of knowing if the signal was sent from an ancestor or descendant namespace. This patch ensures that contianer-init drops all SIG_DFL signals in get_signal_to_deliver() except SIGKILL/SIGSTOP. If SIGSTOP/SIGKILL originate from a descendant of container-init they are never queued (i.e dropped in sig_ignored() in an earler patch). If SIGSTOP/SIGKILL originate from parent namespace, the signal is queued and container-init processes the signal. IOW, if get_signal_to_deliver() sees a sig_kernel_only() signal for global or container-init, the signal must have been generated internally or must have come from an ancestor ns and we process the signal. Further, the signal_group_exit() check was needed to cover the case of a multi-threaded init sending SIGKILL to other threads when doing an exit() or exec(). But since the new sig_kernel_only() check covers the SIGKILL, the signal_group_exit() check is no longer needed and can be removed. Finally, now that we have all pieces in place, set SIGNAL_UNKILLABLE for container-inits. Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Daniel Lezcano <daniel.lezcano@free.fr> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-02 23:58:08 +00:00
!sig_kernel_only(signr))
continue;
if (sig_kernel_stop(signr)) {
/*
* The default action is to stop all threads in
* the thread group. The job control signals
* do nothing in an orphaned pgrp, but SIGSTOP
* always works. Note that siglock needs to be
* dropped during the call to is_orphaned_pgrp()
* because of lock ordering with tasklist_lock.
* This allows an intervening SIGCONT to be posted.
* We need to check for that and bail out if necessary.
*/
if (signr != SIGSTOP) {
spin_unlock_irq(&sighand->siglock);
/* signals can be posted during this window */
if (is_current_pgrp_orphaned())
goto relock;
spin_lock_irq(&sighand->siglock);
}
if (likely(do_signal_stop(ksig->info.si_signo))) {
/* It released the siglock. */
goto relock;
}
/*
* We didn't actually stop, due to a race
* with SIGCONT or something like that.
*/
continue;
}
spin_unlock_irq(&sighand->siglock);
/*
* Anything else is fatal, maybe with a core dump.
*/
current->flags |= PF_SIGNALED;
if (sig_kernel_coredump(signr)) {
if (print_fatal_signals)
print_fatal_signal(ksig->info.si_signo);
proc_coredump_connector(current);
/*
* If it was able to dump core, this kills all
* other threads in the group and synchronizes with
* their demise. If we lost the race with another
* thread getting here, it set group_exit_code
* first and our do_group_exit call below will use
* that value and ignore the one we pass it.
*/
do_coredump(&ksig->info);
}
/*
* Death signals, no core dump.
*/
do_group_exit(ksig->info.si_signo);
/* NOTREACHED */
}
spin_unlock_irq(&sighand->siglock);
ksig->sig = signr;
return ksig->sig > 0;
}
/**
* signal_delivered -
* @ksig: kernel signal struct
* @stepping: nonzero if debugger single-step or block-step in use
*
* This function should be called when a signal has successfully been
* delivered. It updates the blocked signals accordingly (@ksig->ka.sa.sa_mask
* is always blocked, and the signal itself is blocked unless %SA_NODEFER
* is set in @ksig->ka.sa.sa_flags. Tracing is notified.
*/
static void signal_delivered(struct ksignal *ksig, int stepping)
{
sigset_t blocked;
/* A signal was successfully delivered, and the
saved sigmask was stored on the signal frame,
and will be restored by sigreturn. So we can
simply clear the restore sigmask flag. */
clear_restore_sigmask();
sigorsets(&blocked, &current->blocked, &ksig->ka.sa.sa_mask);
if (!(ksig->ka.sa.sa_flags & SA_NODEFER))
sigaddset(&blocked, ksig->sig);
set_current_blocked(&blocked);
tracehook_signal_handler(stepping);
}
void signal_setup_done(int failed, struct ksignal *ksig, int stepping)
{
if (failed)
force_sigsegv(ksig->sig, current);
else
signal_delivered(ksig, stepping);
}
/*
* It could be that complete_signal() picked us to notify about the
* group-wide signal. Other threads should be notified now to take
* the shared signals in @which since we will not.
*/
static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)
{
sigset_t retarget;
struct task_struct *t;
sigandsets(&retarget, &tsk->signal->shared_pending.signal, which);
if (sigisemptyset(&retarget))
return;
t = tsk;
while_each_thread(tsk, t) {
if (t->flags & PF_EXITING)
continue;
if (!has_pending_signals(&retarget, &t->blocked))
continue;
/* Remove the signals this thread can handle. */
sigandsets(&retarget, &retarget, &t->blocked);
if (!signal_pending(t))
signal_wake_up(t, 0);
if (sigisemptyset(&retarget))
break;
}
}
void exit_signals(struct task_struct *tsk)
{
int group_stop = 0;
sigset_t unblocked;
threadgroup: extend threadgroup_lock() to cover exit and exec threadgroup_lock() protected only protected against new addition to the threadgroup, which was inherently somewhat incomplete and problematic for its only user cgroup. On-going migration could race against exec and exit leading to interesting problems - the symmetry between various attach methods, task exiting during method execution, ->exit() racing against attach methods, migrating task switching basic properties during exec and so on. This patch extends threadgroup_lock() such that it protects against all three threadgroup altering operations - fork, exit and exec. For exit, threadgroup_change_begin/end() calls are added to exit_signals around assertion of PF_EXITING. For exec, threadgroup_[un]lock() are updated to also grab and release cred_guard_mutex. With this change, threadgroup_lock() guarantees that the target threadgroup will remain stable - no new task will be added, no new PF_EXITING will be set and exec won't happen. The next patch will update cgroup so that it can take full advantage of this change. -v2: beefed up comment as suggested by Frederic. -v3: narrowed scope of protection in exit path as suggested by Frederic. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Menage <paul@paulmenage.org> Cc: Linus Torvalds <torvalds@linux-foundation.org>
2011-12-13 02:12:21 +00:00
/*
* @tsk is about to have PF_EXITING set - lock out users which
* expect stable threadgroup.
*/
cgroup_threadgroup_change_begin(tsk);
threadgroup: extend threadgroup_lock() to cover exit and exec threadgroup_lock() protected only protected against new addition to the threadgroup, which was inherently somewhat incomplete and problematic for its only user cgroup. On-going migration could race against exec and exit leading to interesting problems - the symmetry between various attach methods, task exiting during method execution, ->exit() racing against attach methods, migrating task switching basic properties during exec and so on. This patch extends threadgroup_lock() such that it protects against all three threadgroup altering operations - fork, exit and exec. For exit, threadgroup_change_begin/end() calls are added to exit_signals around assertion of PF_EXITING. For exec, threadgroup_[un]lock() are updated to also grab and release cred_guard_mutex. With this change, threadgroup_lock() guarantees that the target threadgroup will remain stable - no new task will be added, no new PF_EXITING will be set and exec won't happen. The next patch will update cgroup so that it can take full advantage of this change. -v2: beefed up comment as suggested by Frederic. -v3: narrowed scope of protection in exit path as suggested by Frederic. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Menage <paul@paulmenage.org> Cc: Linus Torvalds <torvalds@linux-foundation.org>
2011-12-13 02:12:21 +00:00
if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
tsk->flags |= PF_EXITING;
cgroup_threadgroup_change_end(tsk);
return;
}
spin_lock_irq(&tsk->sighand->siglock);
/*
* From now this task is not visible for group-wide signals,
* see wants_signal(), do_signal_stop().
*/
tsk->flags |= PF_EXITING;
threadgroup: extend threadgroup_lock() to cover exit and exec threadgroup_lock() protected only protected against new addition to the threadgroup, which was inherently somewhat incomplete and problematic for its only user cgroup. On-going migration could race against exec and exit leading to interesting problems - the symmetry between various attach methods, task exiting during method execution, ->exit() racing against attach methods, migrating task switching basic properties during exec and so on. This patch extends threadgroup_lock() such that it protects against all three threadgroup altering operations - fork, exit and exec. For exit, threadgroup_change_begin/end() calls are added to exit_signals around assertion of PF_EXITING. For exec, threadgroup_[un]lock() are updated to also grab and release cred_guard_mutex. With this change, threadgroup_lock() guarantees that the target threadgroup will remain stable - no new task will be added, no new PF_EXITING will be set and exec won't happen. The next patch will update cgroup so that it can take full advantage of this change. -v2: beefed up comment as suggested by Frederic. -v3: narrowed scope of protection in exit path as suggested by Frederic. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Menage <paul@paulmenage.org> Cc: Linus Torvalds <torvalds@linux-foundation.org>
2011-12-13 02:12:21 +00:00
cgroup_threadgroup_change_end(tsk);
threadgroup: extend threadgroup_lock() to cover exit and exec threadgroup_lock() protected only protected against new addition to the threadgroup, which was inherently somewhat incomplete and problematic for its only user cgroup. On-going migration could race against exec and exit leading to interesting problems - the symmetry between various attach methods, task exiting during method execution, ->exit() racing against attach methods, migrating task switching basic properties during exec and so on. This patch extends threadgroup_lock() such that it protects against all three threadgroup altering operations - fork, exit and exec. For exit, threadgroup_change_begin/end() calls are added to exit_signals around assertion of PF_EXITING. For exec, threadgroup_[un]lock() are updated to also grab and release cred_guard_mutex. With this change, threadgroup_lock() guarantees that the target threadgroup will remain stable - no new task will be added, no new PF_EXITING will be set and exec won't happen. The next patch will update cgroup so that it can take full advantage of this change. -v2: beefed up comment as suggested by Frederic. -v3: narrowed scope of protection in exit path as suggested by Frederic. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Menage <paul@paulmenage.org> Cc: Linus Torvalds <torvalds@linux-foundation.org>
2011-12-13 02:12:21 +00:00
if (!signal_pending(tsk))
goto out;
unblocked = tsk->blocked;
signotset(&unblocked);
retarget_shared_pending(tsk, &unblocked);
if (unlikely(tsk->jobctl & JOBCTL_STOP_PENDING) &&
signal: Fix premature completion of group stop when interfered by ptrace task->signal->group_stop_count is used to track the progress of group stop. It's initialized to the number of tasks which need to stop for group stop to finish and each stopping or trapping task decrements. However, each task doesn't keep track of whether it decremented the counter or not and if woken up before the group stop is complete and stops again, it can decrement the counter multiple times. Please consider the following example code. static void *worker(void *arg) { while (1) ; return NULL; } int main(void) { pthread_t thread; pid_t pid; int i; pid = fork(); if (!pid) { for (i = 0; i < 5; i++) pthread_create(&thread, NULL, worker, NULL); while (1) ; return 0; } ptrace(PTRACE_ATTACH, pid, NULL, NULL); while (1) { waitid(P_PID, pid, NULL, WSTOPPED); ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP); } return 0; } The child creates five threads and the parent continuously traps the first thread and whenever the child gets a signal, SIGSTOP is delivered. If an external process sends SIGSTOP to the child, all other threads in the process should reliably stop. However, due to the above bug, the first thread will often end up consuming group_stop_count multiple times and SIGSTOP often ends up stopping none or part of the other four threads. This patch adds a new field task->group_stop which is protected by siglock and uses GROUP_STOP_CONSUME flag to track which task is still to consume group_stop_count to fix this bug. task_clear_group_stop_pending() and task_participate_group_stop() are added to help manipulating group stop states. As ptrace_stop() now also uses task_participate_group_stop(), it will set SIGNAL_STOP_STOPPED if it completes a group stop. There still are many issues regarding the interaction between group stop and ptrace. Patches to address them will follow. - Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
2011-03-23 09:37:00 +00:00
task_participate_group_stop(tsk))
group_stop = CLD_STOPPED;
out:
spin_unlock_irq(&tsk->sighand->siglock);
/*
* If group stop has completed, deliver the notification. This
* should always go to the real parent of the group leader.
*/
if (unlikely(group_stop)) {
read_lock(&tasklist_lock);
do_notify_parent_cldstop(tsk, false, group_stop);
read_unlock(&tasklist_lock);
}
}
EXPORT_SYMBOL(recalc_sigpending);
EXPORT_SYMBOL_GPL(dequeue_signal);
EXPORT_SYMBOL(flush_signals);
EXPORT_SYMBOL(force_sig);
EXPORT_SYMBOL(send_sig);
EXPORT_SYMBOL(send_sig_info);
EXPORT_SYMBOL(sigprocmask);
/*
* System call entry points.
*/
/**
* sys_restart_syscall - restart a system call
*/
SYSCALL_DEFINE0(restart_syscall)
{
all arches, signal: move restart_block to struct task_struct If an attacker can cause a controlled kernel stack overflow, overwriting the restart block is a very juicy exploit target. This is because the restart_block is held in the same memory allocation as the kernel stack. Moving the restart block to struct task_struct prevents this exploit by making the restart_block harder to locate. Note that there are other fields in thread_info that are also easy targets, at least on some architectures. It's also a decent simplification, since the restart code is more or less identical on all architectures. [james.hogan@imgtec.com: metag: align thread_info::supervisor_stack] Signed-off-by: Andy Lutomirski <luto@amacapital.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: David Miller <davem@davemloft.net> Acked-by: Richard Weinberger <richard@nod.at> Cc: Richard Henderson <rth@twiddle.net> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Matt Turner <mattst88@gmail.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Haavard Skinnemoen <hskinnemoen@gmail.com> Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no> Cc: Steven Miao <realmz6@gmail.com> Cc: Mark Salter <msalter@redhat.com> Cc: Aurelien Jacquiot <a-jacquiot@ti.com> Cc: Mikael Starvik <starvik@axis.com> Cc: Jesper Nilsson <jesper.nilsson@axis.com> Cc: David Howells <dhowells@redhat.com> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Michal Simek <monstr@monstr.eu> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Jonas Bonn <jonas@southpole.se> Cc: "James E.J. Bottomley" <jejb@parisc-linux.org> Cc: Helge Deller <deller@gmx.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) Tested-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Chen Liqin <liqin.linux@gmail.com> Cc: Lennox Wu <lennox.wu@gmail.com> Cc: Chris Metcalf <cmetcalf@ezchip.com> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: Chris Zankel <chris@zankel.net> Cc: Max Filippov <jcmvbkbc@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Guenter Roeck <linux@roeck-us.net> Signed-off-by: James Hogan <james.hogan@imgtec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 23:01:14 +00:00
struct restart_block *restart = &current->restart_block;
return restart->fn(restart);
}
long do_no_restart_syscall(struct restart_block *param)
{
return -EINTR;
}
static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
{
if (signal_pending(tsk) && !thread_group_empty(tsk)) {
sigset_t newblocked;
/* A set of now blocked but previously unblocked signals. */
sigandnsets(&newblocked, newset, &current->blocked);
retarget_shared_pending(tsk, &newblocked);
}
tsk->blocked = *newset;
recalc_sigpending();
}
/**
* set_current_blocked - change current->blocked mask
* @newset: new mask
*
* It is wrong to change ->blocked directly, this helper should be used
* to ensure the process can't miss a shared signal we are going to block.
*/
void set_current_blocked(sigset_t *newset)
{
sigdelsetmask(newset, sigmask(SIGKILL) | sigmask(SIGSTOP));
__set_current_blocked(newset);
}
void __set_current_blocked(const sigset_t *newset)
{
struct task_struct *tsk = current;
signals: avoid unnecessary taking of sighand->siglock When running certain database workload on a high-end system with many CPUs, it was found that spinlock contention in the sigprocmask syscalls became a significant portion of the overall CPU cycles as shown below. 9.30% 9.30% 905387 dataserver /proc/kcore 0x7fff8163f4d2 [k] _raw_spin_lock_irq | ---_raw_spin_lock_irq | |--99.34%-- __set_current_blocked | sigprocmask | sys_rt_sigprocmask | system_call_fastpath | | | |--50.63%-- __swapcontext | | | | | |--99.91%-- upsleepgeneric | | | |--49.36%-- __setcontext | | ktskRun Looking further into the swapcontext function in glibc, it was found that the function always call sigprocmask() without checking if there are changes in the signal mask. A check was added to the __set_current_blocked() function to avoid taking the sighand->siglock spinlock if there is no change in the signal mask. This will prevent unneeded spinlock contention when many threads are trying to call sigprocmask(). With this patch applied, the spinlock contention in sigprocmask() was gone. Link: http://lkml.kernel.org/r/1474979209-11867-1-git-send-email-Waiman.Long@hpe.com Signed-off-by: Waiman Long <Waiman.Long@hpe.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stas Sergeev <stsp@list.ru> Cc: Scott J Norton <scott.norton@hpe.com> Cc: Douglas Hatch <doug.hatch@hpe.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-14 23:04:10 +00:00
/*
* In case the signal mask hasn't changed, there is nothing we need
* to do. The current->blocked shouldn't be modified by other task.
*/
if (sigequalsets(&tsk->blocked, newset))
return;
spin_lock_irq(&tsk->sighand->siglock);
__set_task_blocked(tsk, newset);
spin_unlock_irq(&tsk->sighand->siglock);
}
/*
* This is also useful for kernel threads that want to temporarily
* (or permanently) block certain signals.
*
* NOTE! Unlike the user-mode sys_sigprocmask(), the kernel
* interface happily blocks "unblockable" signals like SIGKILL
* and friends.
*/
int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
{
struct task_struct *tsk = current;
sigset_t newset;
/* Lockless, only current can change ->blocked, never from irq */
if (oldset)
*oldset = tsk->blocked;
switch (how) {
case SIG_BLOCK:
sigorsets(&newset, &tsk->blocked, set);
break;
case SIG_UNBLOCK:
sigandnsets(&newset, &tsk->blocked, set);
break;
case SIG_SETMASK:
newset = *set;
break;
default:
return -EINVAL;
}
__set_current_blocked(&newset);
return 0;
}
/**
* sys_rt_sigprocmask - change the list of currently blocked signals
* @how: whether to add, remove, or set signals
* @nset: stores pending signals
* @oset: previous value of signal mask if non-null
* @sigsetsize: size of sigset_t type
*/
SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset,
sigset_t __user *, oset, size_t, sigsetsize)
{
sigset_t old_set, new_set;
int error;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
old_set = current->blocked;
if (nset) {
if (copy_from_user(&new_set, nset, sizeof(sigset_t)))
return -EFAULT;
sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
error = sigprocmask(how, &new_set, NULL);
if (error)
return error;
}
if (oset) {
if (copy_to_user(oset, &old_set, sizeof(sigset_t)))
return -EFAULT;
}
return 0;
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
compat_sigset_t __user *, oset, compat_size_t, sigsetsize)
{
sigset_t old_set = current->blocked;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
if (nset) {
sigset_t new_set;
int error;
if (get_compat_sigset(&new_set, nset))
return -EFAULT;
sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
error = sigprocmask(how, &new_set, NULL);
if (error)
return error;
}
return oset ? put_compat_sigset(oset, &old_set, sizeof(*oset)) : 0;
}
#endif
static int do_sigpending(sigset_t *set)
{
spin_lock_irq(&current->sighand->siglock);
sigorsets(set, &current->pending.signal,
&current->signal->shared_pending.signal);
spin_unlock_irq(&current->sighand->siglock);
/* Outside the lock because only this thread touches it. */
sigandsets(set, &current->blocked, set);
return 0;
}
/**
* sys_rt_sigpending - examine a pending signal that has been raised
* while blocked
* @uset: stores pending signals
* @sigsetsize: size of sigset_t type or larger
*/
SYSCALL_DEFINE2(rt_sigpending, sigset_t __user *, uset, size_t, sigsetsize)
{
sigset_t set;
int err;
if (sigsetsize > sizeof(*uset))
return -EINVAL;
err = do_sigpending(&set);
if (!err && copy_to_user(uset, &set, sigsetsize))
err = -EFAULT;
return err;
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(rt_sigpending, compat_sigset_t __user *, uset,
compat_size_t, sigsetsize)
{
sigset_t set;
int err;
if (sigsetsize > sizeof(*uset))
return -EINVAL;
err = do_sigpending(&set);
if (!err)
err = put_compat_sigset(uset, &set, sigsetsize);
return err;
}
#endif
signal: Remove kernel interal si_code magic struct siginfo is a union and the kernel since 2.4 has been hiding a union tag in the high 16bits of si_code using the values: __SI_KILL __SI_TIMER __SI_POLL __SI_FAULT __SI_CHLD __SI_RT __SI_MESGQ __SI_SYS While this looks plausible on the surface, in practice this situation has not worked well. - Injected positive signals are not copied to user space properly unless they have these magic high bits set. - Injected positive signals are not reported properly by signalfd unless they have these magic high bits set. - These kernel internal values leaked to userspace via ptrace_peek_siginfo - It was possible to inject these kernel internal values and cause the the kernel to misbehave. - Kernel developers got confused and expected these kernel internal values in userspace in kernel self tests. - Kernel developers got confused and set si_code to __SI_FAULT which is SI_USER in userspace which causes userspace to think an ordinary user sent the signal and that it was not kernel generated. - The values make it impossible to reorganize the code to transform siginfo_copy_to_user into a plain copy_to_user. As si_code must be massaged before being passed to userspace. So remove these kernel internal si codes and make the kernel code simpler and more maintainable. To replace these kernel internal magic si_codes introduce the helper function siginfo_layout, that takes a signal number and an si_code and computes which union member of siginfo is being used. Have siginfo_layout return an enumeration so that gcc will have enough information to warn if a switch statement does not handle all of union members. A couple of architectures have a messed up ABI that defines signal specific duplications of SI_USER which causes more special cases in siginfo_layout than I would like. The good news is only problem architectures pay the cost. Update all of the code that used the previous magic __SI_ values to use the new SIL_ values and to call siginfo_layout to get those values. Escept where not all of the cases are handled remove the defaults in the switch statements so that if a new case is missed in the future the lack will show up at compile time. Modify the code that copies siginfo si_code to userspace to just copy the value and not cast si_code to a short first. The high bits are no longer used to hold a magic union member. Fixup the siginfo header files to stop including the __SI_ values in their constants and for the headers that were missing it to properly update the number of si_codes for each signal type. The fixes to copy_siginfo_from_user32 implementations has the interesting property that several of them perviously should never have worked as the __SI_ values they depended up where kernel internal. With that dependency gone those implementations should work much better. The idea of not passing the __SI_ values out to userspace and then not reinserting them has been tested with criu and criu worked without changes. Ref: 2.4.0-test1 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-07-17 03:36:59 +00:00
enum siginfo_layout siginfo_layout(int sig, int si_code)
{
enum siginfo_layout layout = SIL_KILL;
if ((si_code > SI_USER) && (si_code < SI_KERNEL)) {
static const struct {
unsigned char limit, layout;
} filter[] = {
[SIGILL] = { NSIGILL, SIL_FAULT },
[SIGFPE] = { NSIGFPE, SIL_FAULT },
[SIGSEGV] = { NSIGSEGV, SIL_FAULT },
[SIGBUS] = { NSIGBUS, SIL_FAULT },
[SIGTRAP] = { NSIGTRAP, SIL_FAULT },
#if defined(SIGEMT) && defined(NSIGEMT)
signal: Remove kernel interal si_code magic struct siginfo is a union and the kernel since 2.4 has been hiding a union tag in the high 16bits of si_code using the values: __SI_KILL __SI_TIMER __SI_POLL __SI_FAULT __SI_CHLD __SI_RT __SI_MESGQ __SI_SYS While this looks plausible on the surface, in practice this situation has not worked well. - Injected positive signals are not copied to user space properly unless they have these magic high bits set. - Injected positive signals are not reported properly by signalfd unless they have these magic high bits set. - These kernel internal values leaked to userspace via ptrace_peek_siginfo - It was possible to inject these kernel internal values and cause the the kernel to misbehave. - Kernel developers got confused and expected these kernel internal values in userspace in kernel self tests. - Kernel developers got confused and set si_code to __SI_FAULT which is SI_USER in userspace which causes userspace to think an ordinary user sent the signal and that it was not kernel generated. - The values make it impossible to reorganize the code to transform siginfo_copy_to_user into a plain copy_to_user. As si_code must be massaged before being passed to userspace. So remove these kernel internal si codes and make the kernel code simpler and more maintainable. To replace these kernel internal magic si_codes introduce the helper function siginfo_layout, that takes a signal number and an si_code and computes which union member of siginfo is being used. Have siginfo_layout return an enumeration so that gcc will have enough information to warn if a switch statement does not handle all of union members. A couple of architectures have a messed up ABI that defines signal specific duplications of SI_USER which causes more special cases in siginfo_layout than I would like. The good news is only problem architectures pay the cost. Update all of the code that used the previous magic __SI_ values to use the new SIL_ values and to call siginfo_layout to get those values. Escept where not all of the cases are handled remove the defaults in the switch statements so that if a new case is missed in the future the lack will show up at compile time. Modify the code that copies siginfo si_code to userspace to just copy the value and not cast si_code to a short first. The high bits are no longer used to hold a magic union member. Fixup the siginfo header files to stop including the __SI_ values in their constants and for the headers that were missing it to properly update the number of si_codes for each signal type. The fixes to copy_siginfo_from_user32 implementations has the interesting property that several of them perviously should never have worked as the __SI_ values they depended up where kernel internal. With that dependency gone those implementations should work much better. The idea of not passing the __SI_ values out to userspace and then not reinserting them has been tested with criu and criu worked without changes. Ref: 2.4.0-test1 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-07-17 03:36:59 +00:00
[SIGEMT] = { NSIGEMT, SIL_FAULT },
#endif
[SIGCHLD] = { NSIGCHLD, SIL_CHLD },
[SIGPOLL] = { NSIGPOLL, SIL_POLL },
[SIGSYS] = { NSIGSYS, SIL_SYS },
};
if ((sig < ARRAY_SIZE(filter)) && (si_code <= filter[sig].limit)) {
signal: Remove kernel interal si_code magic struct siginfo is a union and the kernel since 2.4 has been hiding a union tag in the high 16bits of si_code using the values: __SI_KILL __SI_TIMER __SI_POLL __SI_FAULT __SI_CHLD __SI_RT __SI_MESGQ __SI_SYS While this looks plausible on the surface, in practice this situation has not worked well. - Injected positive signals are not copied to user space properly unless they have these magic high bits set. - Injected positive signals are not reported properly by signalfd unless they have these magic high bits set. - These kernel internal values leaked to userspace via ptrace_peek_siginfo - It was possible to inject these kernel internal values and cause the the kernel to misbehave. - Kernel developers got confused and expected these kernel internal values in userspace in kernel self tests. - Kernel developers got confused and set si_code to __SI_FAULT which is SI_USER in userspace which causes userspace to think an ordinary user sent the signal and that it was not kernel generated. - The values make it impossible to reorganize the code to transform siginfo_copy_to_user into a plain copy_to_user. As si_code must be massaged before being passed to userspace. So remove these kernel internal si codes and make the kernel code simpler and more maintainable. To replace these kernel internal magic si_codes introduce the helper function siginfo_layout, that takes a signal number and an si_code and computes which union member of siginfo is being used. Have siginfo_layout return an enumeration so that gcc will have enough information to warn if a switch statement does not handle all of union members. A couple of architectures have a messed up ABI that defines signal specific duplications of SI_USER which causes more special cases in siginfo_layout than I would like. The good news is only problem architectures pay the cost. Update all of the code that used the previous magic __SI_ values to use the new SIL_ values and to call siginfo_layout to get those values. Escept where not all of the cases are handled remove the defaults in the switch statements so that if a new case is missed in the future the lack will show up at compile time. Modify the code that copies siginfo si_code to userspace to just copy the value and not cast si_code to a short first. The high bits are no longer used to hold a magic union member. Fixup the siginfo header files to stop including the __SI_ values in their constants and for the headers that were missing it to properly update the number of si_codes for each signal type. The fixes to copy_siginfo_from_user32 implementations has the interesting property that several of them perviously should never have worked as the __SI_ values they depended up where kernel internal. With that dependency gone those implementations should work much better. The idea of not passing the __SI_ values out to userspace and then not reinserting them has been tested with criu and criu worked without changes. Ref: 2.4.0-test1 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-07-17 03:36:59 +00:00
layout = filter[sig].layout;
/* Handle the exceptions */
if ((sig == SIGBUS) &&
(si_code >= BUS_MCEERR_AR) && (si_code <= BUS_MCEERR_AO))
layout = SIL_FAULT_MCEERR;
else if ((sig == SIGSEGV) && (si_code == SEGV_BNDERR))
layout = SIL_FAULT_BNDERR;
#ifdef SEGV_PKUERR
else if ((sig == SIGSEGV) && (si_code == SEGV_PKUERR))
layout = SIL_FAULT_PKUERR;
#endif
}
signal: Remove kernel interal si_code magic struct siginfo is a union and the kernel since 2.4 has been hiding a union tag in the high 16bits of si_code using the values: __SI_KILL __SI_TIMER __SI_POLL __SI_FAULT __SI_CHLD __SI_RT __SI_MESGQ __SI_SYS While this looks plausible on the surface, in practice this situation has not worked well. - Injected positive signals are not copied to user space properly unless they have these magic high bits set. - Injected positive signals are not reported properly by signalfd unless they have these magic high bits set. - These kernel internal values leaked to userspace via ptrace_peek_siginfo - It was possible to inject these kernel internal values and cause the the kernel to misbehave. - Kernel developers got confused and expected these kernel internal values in userspace in kernel self tests. - Kernel developers got confused and set si_code to __SI_FAULT which is SI_USER in userspace which causes userspace to think an ordinary user sent the signal and that it was not kernel generated. - The values make it impossible to reorganize the code to transform siginfo_copy_to_user into a plain copy_to_user. As si_code must be massaged before being passed to userspace. So remove these kernel internal si codes and make the kernel code simpler and more maintainable. To replace these kernel internal magic si_codes introduce the helper function siginfo_layout, that takes a signal number and an si_code and computes which union member of siginfo is being used. Have siginfo_layout return an enumeration so that gcc will have enough information to warn if a switch statement does not handle all of union members. A couple of architectures have a messed up ABI that defines signal specific duplications of SI_USER which causes more special cases in siginfo_layout than I would like. The good news is only problem architectures pay the cost. Update all of the code that used the previous magic __SI_ values to use the new SIL_ values and to call siginfo_layout to get those values. Escept where not all of the cases are handled remove the defaults in the switch statements so that if a new case is missed in the future the lack will show up at compile time. Modify the code that copies siginfo si_code to userspace to just copy the value and not cast si_code to a short first. The high bits are no longer used to hold a magic union member. Fixup the siginfo header files to stop including the __SI_ values in their constants and for the headers that were missing it to properly update the number of si_codes for each signal type. The fixes to copy_siginfo_from_user32 implementations has the interesting property that several of them perviously should never have worked as the __SI_ values they depended up where kernel internal. With that dependency gone those implementations should work much better. The idea of not passing the __SI_ values out to userspace and then not reinserting them has been tested with criu and criu worked without changes. Ref: 2.4.0-test1 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-07-17 03:36:59 +00:00
else if (si_code <= NSIGPOLL)
layout = SIL_POLL;
} else {
if (si_code == SI_TIMER)
layout = SIL_TIMER;
else if (si_code == SI_SIGIO)
layout = SIL_POLL;
else if (si_code < 0)
layout = SIL_RT;
}
return layout;
}
int copy_siginfo_to_user(siginfo_t __user *to, const siginfo_t *from)
{
if (copy_to_user(to, from , sizeof(struct siginfo)))
return -EFAULT;
return 0;
}
#ifdef CONFIG_COMPAT
int copy_siginfo_to_user32(struct compat_siginfo __user *to,
const struct siginfo *from)
#if defined(CONFIG_X86_X32_ABI) || defined(CONFIG_IA32_EMULATION)
{
return __copy_siginfo_to_user32(to, from, in_x32_syscall());
}
int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
const struct siginfo *from, bool x32_ABI)
#endif
{
struct compat_siginfo new;
memset(&new, 0, sizeof(new));
new.si_signo = from->si_signo;
new.si_errno = from->si_errno;
new.si_code = from->si_code;
switch(siginfo_layout(from->si_signo, from->si_code)) {
case SIL_KILL:
new.si_pid = from->si_pid;
new.si_uid = from->si_uid;
break;
case SIL_TIMER:
new.si_tid = from->si_tid;
new.si_overrun = from->si_overrun;
new.si_int = from->si_int;
break;
case SIL_POLL:
new.si_band = from->si_band;
new.si_fd = from->si_fd;
break;
case SIL_FAULT:
new.si_addr = ptr_to_compat(from->si_addr);
#ifdef __ARCH_SI_TRAPNO
new.si_trapno = from->si_trapno;
#endif
break;
case SIL_FAULT_MCEERR:
new.si_addr = ptr_to_compat(from->si_addr);
#ifdef __ARCH_SI_TRAPNO
new.si_trapno = from->si_trapno;
#endif
new.si_addr_lsb = from->si_addr_lsb;
break;
case SIL_FAULT_BNDERR:
new.si_addr = ptr_to_compat(from->si_addr);
#ifdef __ARCH_SI_TRAPNO
new.si_trapno = from->si_trapno;
#endif
new.si_lower = ptr_to_compat(from->si_lower);
new.si_upper = ptr_to_compat(from->si_upper);
break;
case SIL_FAULT_PKUERR:
new.si_addr = ptr_to_compat(from->si_addr);
#ifdef __ARCH_SI_TRAPNO
new.si_trapno = from->si_trapno;
#endif
new.si_pkey = from->si_pkey;
break;
case SIL_CHLD:
new.si_pid = from->si_pid;
new.si_uid = from->si_uid;
new.si_status = from->si_status;
#ifdef CONFIG_X86_X32_ABI
if (x32_ABI) {
new._sifields._sigchld_x32._utime = from->si_utime;
new._sifields._sigchld_x32._stime = from->si_stime;
} else
#endif
{
new.si_utime = from->si_utime;
new.si_stime = from->si_stime;
}
break;
case SIL_RT:
new.si_pid = from->si_pid;
new.si_uid = from->si_uid;
new.si_int = from->si_int;
break;
case SIL_SYS:
new.si_call_addr = ptr_to_compat(from->si_call_addr);
new.si_syscall = from->si_syscall;
new.si_arch = from->si_arch;
break;
}
if (copy_to_user(to, &new, sizeof(struct compat_siginfo)))
return -EFAULT;
return 0;
}
int copy_siginfo_from_user32(struct siginfo *to,
const struct compat_siginfo __user *ufrom)
{
struct compat_siginfo from;
if (copy_from_user(&from, ufrom, sizeof(struct compat_siginfo)))
return -EFAULT;
clear_siginfo(to);
to->si_signo = from.si_signo;
to->si_errno = from.si_errno;
to->si_code = from.si_code;
switch(siginfo_layout(from.si_signo, from.si_code)) {
case SIL_KILL:
to->si_pid = from.si_pid;
to->si_uid = from.si_uid;
break;
case SIL_TIMER:
to->si_tid = from.si_tid;
to->si_overrun = from.si_overrun;
to->si_int = from.si_int;
break;
case SIL_POLL:
to->si_band = from.si_band;
to->si_fd = from.si_fd;
break;
case SIL_FAULT:
to->si_addr = compat_ptr(from.si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from.si_trapno;
#endif
break;
case SIL_FAULT_MCEERR:
to->si_addr = compat_ptr(from.si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from.si_trapno;
#endif
to->si_addr_lsb = from.si_addr_lsb;
break;
case SIL_FAULT_BNDERR:
to->si_addr = compat_ptr(from.si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from.si_trapno;
#endif
to->si_lower = compat_ptr(from.si_lower);
to->si_upper = compat_ptr(from.si_upper);
break;
case SIL_FAULT_PKUERR:
to->si_addr = compat_ptr(from.si_addr);
#ifdef __ARCH_SI_TRAPNO
to->si_trapno = from.si_trapno;
#endif
to->si_pkey = from.si_pkey;
break;
case SIL_CHLD:
to->si_pid = from.si_pid;
to->si_uid = from.si_uid;
to->si_status = from.si_status;
#ifdef CONFIG_X86_X32_ABI
if (in_x32_syscall()) {
to->si_utime = from._sifields._sigchld_x32._utime;
to->si_stime = from._sifields._sigchld_x32._stime;
} else
#endif
{
to->si_utime = from.si_utime;
to->si_stime = from.si_stime;
}
break;
case SIL_RT:
to->si_pid = from.si_pid;
to->si_uid = from.si_uid;
to->si_int = from.si_int;
break;
case SIL_SYS:
to->si_call_addr = compat_ptr(from.si_call_addr);
to->si_syscall = from.si_syscall;
to->si_arch = from.si_arch;
break;
}
return 0;
}
#endif /* CONFIG_COMPAT */
/**
* do_sigtimedwait - wait for queued signals specified in @which
* @which: queued signals to wait for
* @info: if non-null, the signal's siginfo is returned here
* @ts: upper bound on process time suspension
*/
static int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
const struct timespec *ts)
{
ktime_t *to = NULL, timeout = KTIME_MAX;
struct task_struct *tsk = current;
sigset_t mask = *which;
int sig, ret = 0;
if (ts) {
if (!timespec_valid(ts))
return -EINVAL;
timeout = timespec_to_ktime(*ts);
to = &timeout;
}
/*
* Invert the set of allowed signals to get those we want to block.
*/
sigdelsetmask(&mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
signotset(&mask);
spin_lock_irq(&tsk->sighand->siglock);
sig = dequeue_signal(tsk, &mask, info);
if (!sig && timeout) {
/*
* None ready, temporarily unblock those we're interested
* while we are sleeping in so that we'll be awakened when
* they arrive. Unblocking is always fine, we can avoid
* set_current_blocked().
*/
tsk->real_blocked = tsk->blocked;
sigandsets(&tsk->blocked, &tsk->blocked, &mask);
recalc_sigpending();
spin_unlock_irq(&tsk->sighand->siglock);
__set_current_state(TASK_INTERRUPTIBLE);
ret = freezable_schedule_hrtimeout_range(to, tsk->timer_slack_ns,
HRTIMER_MODE_REL);
spin_lock_irq(&tsk->sighand->siglock);
__set_task_blocked(tsk, &tsk->real_blocked);
sigemptyset(&tsk->real_blocked);
sig = dequeue_signal(tsk, &mask, info);
}
spin_unlock_irq(&tsk->sighand->siglock);
if (sig)
return sig;
return ret ? -EINTR : -EAGAIN;
}
/**
* sys_rt_sigtimedwait - synchronously wait for queued signals specified
* in @uthese
* @uthese: queued signals to wait for
* @uinfo: if non-null, the signal's siginfo is returned here
* @uts: upper bound on process time suspension
* @sigsetsize: size of sigset_t type
*/
SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
siginfo_t __user *, uinfo, const struct timespec __user *, uts,
size_t, sigsetsize)
{
sigset_t these;
struct timespec ts;
siginfo_t info;
int ret;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
if (copy_from_user(&these, uthese, sizeof(these)))
return -EFAULT;
if (uts) {
if (copy_from_user(&ts, uts, sizeof(ts)))
return -EFAULT;
}
ret = do_sigtimedwait(&these, &info, uts ? &ts : NULL);
if (ret > 0 && uinfo) {
if (copy_siginfo_to_user(uinfo, &info))
ret = -EFAULT;
}
return ret;
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(rt_sigtimedwait, compat_sigset_t __user *, uthese,
struct compat_siginfo __user *, uinfo,
struct compat_timespec __user *, uts, compat_size_t, sigsetsize)
{
sigset_t s;
struct timespec t;
siginfo_t info;
long ret;
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
if (get_compat_sigset(&s, uthese))
return -EFAULT;
if (uts) {
if (compat_get_timespec(&t, uts))
return -EFAULT;
}
ret = do_sigtimedwait(&s, &info, uts ? &t : NULL);
if (ret > 0 && uinfo) {
if (copy_siginfo_to_user32(uinfo, &info))
ret = -EFAULT;
}
return ret;
}
#endif
/**
* sys_kill - send a signal to a process
* @pid: the PID of the process
* @sig: signal to be sent
*/
SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
{
struct siginfo info;
clear_siginfo(&info);
info.si_signo = sig;
info.si_errno = 0;
info.si_code = SI_USER;
info.si_pid = task_tgid_vnr(current);
info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
return kill_something_info(sig, &info, pid);
}
static int
do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info)
{
struct task_struct *p;
int error = -ESRCH;
rcu_read_lock();
p = find_task_by_vpid(pid);
if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
error = check_kill_permission(sig, info, p);
/*
* The null signal is a permissions and process existence
* probe. No signal is actually delivered.
*/
if (!error && sig) {
error = do_send_sig_info(sig, info, p, false);
/*
* If lock_task_sighand() failed we pretend the task
* dies after receiving the signal. The window is tiny,
* and the signal is private anyway.
*/
if (unlikely(error == -ESRCH))
error = 0;
}
}
rcu_read_unlock();
return error;
}
static int do_tkill(pid_t tgid, pid_t pid, int sig)
{
struct siginfo info;
clear_siginfo(&info);
info.si_signo = sig;
info.si_errno = 0;
info.si_code = SI_TKILL;
info.si_pid = task_tgid_vnr(current);
info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
return do_send_specific(tgid, pid, sig, &info);
}
/**
* sys_tgkill - send signal to one specific thread
* @tgid: the thread group ID of the thread
* @pid: the PID of the thread
* @sig: signal to be sent
*
* This syscall also checks the @tgid and returns -ESRCH even if the PID
* exists but it's not belonging to the target process anymore. This
* method solves the problem of threads exiting and PIDs getting reused.
*/
SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig)
{
/* This is only valid for single tasks */
if (pid <= 0 || tgid <= 0)
return -EINVAL;
return do_tkill(tgid, pid, sig);
}
/**
* sys_tkill - send signal to one specific task
* @pid: the PID of the task
* @sig: signal to be sent
*
* Send a signal to only one task, even if it's a CLONE_THREAD task.
*/
SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
{
/* This is only valid for single tasks */
if (pid <= 0)
return -EINVAL;
return do_tkill(0, pid, sig);
}
static int do_rt_sigqueueinfo(pid_t pid, int sig, siginfo_t *info)
{
/* Not even root can pretend to send signals from the kernel.
* Nor can they impersonate a kill()/tgkill(), which adds source info.
*/
signal: allow to send any siginfo to itself The idea is simple. We need to get the siginfo for each signal on checkpointing dump, and then return it back on restore. The first problem is that the kernel doesn't report complete siginfos to userspace. In a signal handler the kernel strips SI_CODE from siginfo. When a siginfo is received from signalfd, it has a different format with fixed sizes of fields. The interface of signalfd was extended. If a signalfd is created with the flag SFD_RAW, it returns siginfo in a raw format. rt_sigqueueinfo looks suitable for restoring signals, but it can't send siginfo with a positive si_code, because these codes are reserved for the kernel. In the real world each person has right to do anything with himself, so I think a process should able to send any siginfo to itself. This patch: The kernel prevents sending of siginfo with positive si_code, because these codes are reserved for kernel. I think we can allow a task to send such a siginfo to itself. This operation should not be dangerous. This functionality is required for restoring signals in checkpoint/restart. Signed-off-by: Andrey Vagin <avagin@openvz.org> Cc: Serge Hallyn <serge.hallyn@canonical.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-28 01:03:12 +00:00
if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
(task_pid_vnr(current) != pid))
return -EPERM;
info->si_signo = sig;
/* POSIX.1b doesn't mention process groups. */
return kill_proc_info(sig, info, pid);
}
/**
* sys_rt_sigqueueinfo - send signal information to a signal
* @pid: the PID of the thread
* @sig: signal to be sent
* @uinfo: signal info to be sent
*/
SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
siginfo_t __user *, uinfo)
{
siginfo_t info;
if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
return -EFAULT;
return do_rt_sigqueueinfo(pid, sig, &info);
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(rt_sigqueueinfo,
compat_pid_t, pid,
int, sig,
struct compat_siginfo __user *, uinfo)
{
siginfo_t info;
int ret = copy_siginfo_from_user32(&info, uinfo);
if (unlikely(ret))
return ret;
return do_rt_sigqueueinfo(pid, sig, &info);
}
#endif
static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
{
/* This is only valid for single tasks */
if (pid <= 0 || tgid <= 0)
return -EINVAL;
/* Not even root can pretend to send signals from the kernel.
* Nor can they impersonate a kill()/tgkill(), which adds source info.
*/
if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
(task_pid_vnr(current) != pid))
return -EPERM;
info->si_signo = sig;
return do_send_specific(tgid, pid, sig, info);
}
SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig,
siginfo_t __user *, uinfo)
{
siginfo_t info;
if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
return -EFAULT;
return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(rt_tgsigqueueinfo,
compat_pid_t, tgid,
compat_pid_t, pid,
int, sig,
struct compat_siginfo __user *, uinfo)
{
siginfo_t info;
if (copy_siginfo_from_user32(&info, uinfo))
return -EFAULT;
return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
}
#endif
/*
* For kthreads only, must not be used if cloned with CLONE_SIGHAND
*/
void kernel_sigaction(int sig, __sighandler_t action)
{
spin_lock_irq(&current->sighand->siglock);
current->sighand->action[sig - 1].sa.sa_handler = action;
if (action == SIG_IGN) {
sigset_t mask;
sigemptyset(&mask);
sigaddset(&mask, sig);
flush_sigqueue_mask(&mask, &current->signal->shared_pending);
flush_sigqueue_mask(&mask, &current->pending);
recalc_sigpending();
}
spin_unlock_irq(&current->sighand->siglock);
}
EXPORT_SYMBOL(kernel_sigaction);
void __weak sigaction_compat_abi(struct k_sigaction *act,
struct k_sigaction *oact)
{
}
int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
{
struct task_struct *p = current, *t;
struct k_sigaction *k;
sigset_t mask;
if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
return -EINVAL;
k = &p->sighand->action[sig-1];
spin_lock_irq(&p->sighand->siglock);
if (oact)
*oact = *k;
sigaction_compat_abi(act, oact);
if (act) {
sigdelsetmask(&act->sa.sa_mask,
sigmask(SIGKILL) | sigmask(SIGSTOP));
*k = *act;
/*
* POSIX 3.3.1.3:
* "Setting a signal action to SIG_IGN for a signal that is
* pending shall cause the pending signal to be discarded,
* whether or not it is blocked."
*
* "Setting a signal action to SIG_DFL for a signal that is
* pending and whose default action is to ignore the signal
* (for example, SIGCHLD), shall cause the pending signal to
* be discarded, whether or not it is blocked"
*/
if (sig_handler_ignored(sig_handler(p, sig), sig)) {
sigemptyset(&mask);
sigaddset(&mask, sig);
flush_sigqueue_mask(&mask, &p->signal->shared_pending);
for_each_thread(p, t)
flush_sigqueue_mask(&mask, &t->pending);
}
}
spin_unlock_irq(&p->sighand->siglock);
return 0;
}
static int
do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp)
{
struct task_struct *t = current;
if (oss) {
memset(oss, 0, sizeof(stack_t));
oss->ss_sp = (void __user *) t->sas_ss_sp;
oss->ss_size = t->sas_ss_size;
oss->ss_flags = sas_ss_flags(sp) |
(current->sas_ss_flags & SS_FLAG_BITS);
}
if (ss) {
void __user *ss_sp = ss->ss_sp;
size_t ss_size = ss->ss_size;
unsigned ss_flags = ss->ss_flags;
signals/sigaltstack: Prepare to add new SS_xxx flags This patch adds SS_FLAG_BITS - the mask that splits sigaltstack mode values and bit-flags. Since there is no bit-flags yet, the mask is defined to 0. The flags are added by subsequent patches. With every new flag, the mask should have the appropriate bit cleared. This makes sure if some flag is tried on a kernel that doesn't support it, the -EINVAL error will be returned, because such a flag will be treated as an invalid mode rather than the bit-flag. That way the existence of the particular features can be probed at run-time. This change was suggested by Andy Lutomirski: https://lkml.org/lkml/2016/3/6/158 Signed-off-by: Stas Sergeev <stsp@list.ru> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Amanieu d'Antras <amanieu@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Richard Weinberger <richard@nod.at> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: linux-api@vger.kernel.org Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1460665206-13646-3-git-send-email-stsp@list.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-14 20:20:03 +00:00
int ss_mode;
if (unlikely(on_sig_stack(sp)))
return -EPERM;
signals/sigaltstack: Prepare to add new SS_xxx flags This patch adds SS_FLAG_BITS - the mask that splits sigaltstack mode values and bit-flags. Since there is no bit-flags yet, the mask is defined to 0. The flags are added by subsequent patches. With every new flag, the mask should have the appropriate bit cleared. This makes sure if some flag is tried on a kernel that doesn't support it, the -EINVAL error will be returned, because such a flag will be treated as an invalid mode rather than the bit-flag. That way the existence of the particular features can be probed at run-time. This change was suggested by Andy Lutomirski: https://lkml.org/lkml/2016/3/6/158 Signed-off-by: Stas Sergeev <stsp@list.ru> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Amanieu d'Antras <amanieu@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Richard Weinberger <richard@nod.at> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: linux-api@vger.kernel.org Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1460665206-13646-3-git-send-email-stsp@list.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-14 20:20:03 +00:00
ss_mode = ss_flags & ~SS_FLAG_BITS;
if (unlikely(ss_mode != SS_DISABLE && ss_mode != SS_ONSTACK &&
ss_mode != 0))
return -EINVAL;
signals/sigaltstack: Prepare to add new SS_xxx flags This patch adds SS_FLAG_BITS - the mask that splits sigaltstack mode values and bit-flags. Since there is no bit-flags yet, the mask is defined to 0. The flags are added by subsequent patches. With every new flag, the mask should have the appropriate bit cleared. This makes sure if some flag is tried on a kernel that doesn't support it, the -EINVAL error will be returned, because such a flag will be treated as an invalid mode rather than the bit-flag. That way the existence of the particular features can be probed at run-time. This change was suggested by Andy Lutomirski: https://lkml.org/lkml/2016/3/6/158 Signed-off-by: Stas Sergeev <stsp@list.ru> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Amanieu d'Antras <amanieu@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Richard Weinberger <richard@nod.at> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: linux-api@vger.kernel.org Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1460665206-13646-3-git-send-email-stsp@list.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-14 20:20:03 +00:00
if (ss_mode == SS_DISABLE) {
ss_size = 0;
ss_sp = NULL;
} else {
if (unlikely(ss_size < MINSIGSTKSZ))
return -ENOMEM;
}
t->sas_ss_sp = (unsigned long) ss_sp;
t->sas_ss_size = ss_size;
t->sas_ss_flags = ss_flags;
}
return 0;
}
SYSCALL_DEFINE2(sigaltstack,const stack_t __user *,uss, stack_t __user *,uoss)
{
stack_t new, old;
int err;
if (uss && copy_from_user(&new, uss, sizeof(stack_t)))
return -EFAULT;
err = do_sigaltstack(uss ? &new : NULL, uoss ? &old : NULL,
current_user_stack_pointer());
if (!err && uoss && copy_to_user(uoss, &old, sizeof(stack_t)))
err = -EFAULT;
return err;
}
int restore_altstack(const stack_t __user *uss)
{
stack_t new;
if (copy_from_user(&new, uss, sizeof(stack_t)))
return -EFAULT;
(void)do_sigaltstack(&new, NULL, current_user_stack_pointer());
/* squash all but EFAULT for now */
return 0;
}
int __save_altstack(stack_t __user *uss, unsigned long sp)
{
struct task_struct *t = current;
signals/sigaltstack: Implement SS_AUTODISARM flag This patch implements the SS_AUTODISARM flag that can be OR-ed with SS_ONSTACK when forming ss_flags. When this flag is set, sigaltstack will be disabled when entering the signal handler; more precisely, after saving sas to uc_stack. When leaving the signal handler, the sigaltstack is restored by uc_stack. When this flag is used, it is safe to switch from sighandler with swapcontext(). Without this flag, the subsequent signal will corrupt the state of the switched-away sighandler. To detect the support of this functionality, one can do: err = sigaltstack(SS_DISABLE | SS_AUTODISARM); if (err && errno == EINVAL) unsupported(); Signed-off-by: Stas Sergeev <stsp@list.ru> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Aleksa Sarai <cyphar@cyphar.com> Cc: Amanieu d'Antras <amanieu@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Heinrich Schuchardt <xypron.glpk@gmx.de> Cc: Jason Low <jason.low2@hp.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Paul Moore <pmoore@redhat.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Richard Weinberger <richard@nod.at> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: linux-api@vger.kernel.org Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1460665206-13646-4-git-send-email-stsp@list.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-14 20:20:04 +00:00
int err = __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) |
__put_user(t->sas_ss_flags, &uss->ss_flags) |
__put_user(t->sas_ss_size, &uss->ss_size);
signals/sigaltstack: Implement SS_AUTODISARM flag This patch implements the SS_AUTODISARM flag that can be OR-ed with SS_ONSTACK when forming ss_flags. When this flag is set, sigaltstack will be disabled when entering the signal handler; more precisely, after saving sas to uc_stack. When leaving the signal handler, the sigaltstack is restored by uc_stack. When this flag is used, it is safe to switch from sighandler with swapcontext(). Without this flag, the subsequent signal will corrupt the state of the switched-away sighandler. To detect the support of this functionality, one can do: err = sigaltstack(SS_DISABLE | SS_AUTODISARM); if (err && errno == EINVAL) unsupported(); Signed-off-by: Stas Sergeev <stsp@list.ru> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Aleksa Sarai <cyphar@cyphar.com> Cc: Amanieu d'Antras <amanieu@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Heinrich Schuchardt <xypron.glpk@gmx.de> Cc: Jason Low <jason.low2@hp.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Paul Moore <pmoore@redhat.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Richard Weinberger <richard@nod.at> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: linux-api@vger.kernel.org Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1460665206-13646-4-git-send-email-stsp@list.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-14 20:20:04 +00:00
if (err)
return err;
if (t->sas_ss_flags & SS_AUTODISARM)
sas_ss_reset(t);
return 0;
}
#ifdef CONFIG_COMPAT
static int do_compat_sigaltstack(const compat_stack_t __user *uss_ptr,
compat_stack_t __user *uoss_ptr)
{
stack_t uss, uoss;
int ret;
if (uss_ptr) {
compat_stack_t uss32;
if (copy_from_user(&uss32, uss_ptr, sizeof(compat_stack_t)))
return -EFAULT;
uss.ss_sp = compat_ptr(uss32.ss_sp);
uss.ss_flags = uss32.ss_flags;
uss.ss_size = uss32.ss_size;
}
ret = do_sigaltstack(uss_ptr ? &uss : NULL, &uoss,
compat_user_stack_pointer());
if (ret >= 0 && uoss_ptr) {
compat_stack_t old;
memset(&old, 0, sizeof(old));
old.ss_sp = ptr_to_compat(uoss.ss_sp);
old.ss_flags = uoss.ss_flags;
old.ss_size = uoss.ss_size;
if (copy_to_user(uoss_ptr, &old, sizeof(compat_stack_t)))
ret = -EFAULT;
}
return ret;
}
COMPAT_SYSCALL_DEFINE2(sigaltstack,
const compat_stack_t __user *, uss_ptr,
compat_stack_t __user *, uoss_ptr)
{
return do_compat_sigaltstack(uss_ptr, uoss_ptr);
}
int compat_restore_altstack(const compat_stack_t __user *uss)
{
int err = do_compat_sigaltstack(uss, NULL);
/* squash all but -EFAULT for now */
return err == -EFAULT ? err : 0;
}
int __compat_save_altstack(compat_stack_t __user *uss, unsigned long sp)
{
int err;
struct task_struct *t = current;
err = __put_user(ptr_to_compat((void __user *)t->sas_ss_sp),
&uss->ss_sp) |
__put_user(t->sas_ss_flags, &uss->ss_flags) |
__put_user(t->sas_ss_size, &uss->ss_size);
if (err)
return err;
if (t->sas_ss_flags & SS_AUTODISARM)
sas_ss_reset(t);
return 0;
}
#endif
#ifdef __ARCH_WANT_SYS_SIGPENDING
/**
* sys_sigpending - examine pending signals
* @uset: where mask of pending signal is returned
*/
SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, uset)
{
sigset_t set;
int err;
if (sizeof(old_sigset_t) > sizeof(*uset))
return -EINVAL;
err = do_sigpending(&set);
if (!err && copy_to_user(uset, &set, sizeof(old_sigset_t)))
err = -EFAULT;
return err;
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE1(sigpending, compat_old_sigset_t __user *, set32)
{
sigset_t set;
int err = do_sigpending(&set);
if (!err)
err = put_user(set.sig[0], set32);
return err;
}
#endif
#endif
#ifdef __ARCH_WANT_SYS_SIGPROCMASK
/**
* sys_sigprocmask - examine and change blocked signals
* @how: whether to add, remove, or set signals
* @nset: signals to add or remove (if non-null)
* @oset: previous value of signal mask if non-null
*
* Some platforms have their own version with special arguments;
* others support only sys_rt_sigprocmask.
*/
SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset,
old_sigset_t __user *, oset)
{
old_sigset_t old_set, new_set;
sigset_t new_blocked;
old_set = current->blocked.sig[0];
if (nset) {
if (copy_from_user(&new_set, nset, sizeof(*nset)))
return -EFAULT;
new_blocked = current->blocked;
switch (how) {
case SIG_BLOCK:
sigaddsetmask(&new_blocked, new_set);
break;
case SIG_UNBLOCK:
sigdelsetmask(&new_blocked, new_set);
break;
case SIG_SETMASK:
new_blocked.sig[0] = new_set;
break;
default:
return -EINVAL;
}
set_current_blocked(&new_blocked);
}
if (oset) {
if (copy_to_user(oset, &old_set, sizeof(*oset)))
return -EFAULT;
}
return 0;
}
#endif /* __ARCH_WANT_SYS_SIGPROCMASK */
#ifndef CONFIG_ODD_RT_SIGACTION
/**
* sys_rt_sigaction - alter an action taken by a process
* @sig: signal to be sent
* @act: new sigaction
* @oact: used to save the previous sigaction
* @sigsetsize: size of sigset_t type
*/
SYSCALL_DEFINE4(rt_sigaction, int, sig,
const struct sigaction __user *, act,
struct sigaction __user *, oact,
size_t, sigsetsize)
{
struct k_sigaction new_sa, old_sa;
int ret = -EINVAL;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
goto out;
if (act) {
if (copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa)))
return -EFAULT;
}
ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
if (!ret && oact) {
if (copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa)))
return -EFAULT;
}
out:
return ret;
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(rt_sigaction, int, sig,
const struct compat_sigaction __user *, act,
struct compat_sigaction __user *, oact,
compat_size_t, sigsetsize)
{
struct k_sigaction new_ka, old_ka;
#ifdef __ARCH_HAS_SA_RESTORER
compat_uptr_t restorer;
#endif
int ret;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(compat_sigset_t))
return -EINVAL;
if (act) {
compat_uptr_t handler;
ret = get_user(handler, &act->sa_handler);
new_ka.sa.sa_handler = compat_ptr(handler);
#ifdef __ARCH_HAS_SA_RESTORER
ret |= get_user(restorer, &act->sa_restorer);
new_ka.sa.sa_restorer = compat_ptr(restorer);
#endif
ret |= get_compat_sigset(&new_ka.sa.sa_mask, &act->sa_mask);
ret |= get_user(new_ka.sa.sa_flags, &act->sa_flags);
if (ret)
return -EFAULT;
}
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
ret = put_user(ptr_to_compat(old_ka.sa.sa_handler),
&oact->sa_handler);
ret |= put_compat_sigset(&oact->sa_mask, &old_ka.sa.sa_mask,
sizeof(oact->sa_mask));
ret |= put_user(old_ka.sa.sa_flags, &oact->sa_flags);
#ifdef __ARCH_HAS_SA_RESTORER
ret |= put_user(ptr_to_compat(old_ka.sa.sa_restorer),
&oact->sa_restorer);
#endif
}
return ret;
}
#endif
#endif /* !CONFIG_ODD_RT_SIGACTION */
#ifdef CONFIG_OLD_SIGACTION
SYSCALL_DEFINE3(sigaction, int, sig,
const struct old_sigaction __user *, act,
struct old_sigaction __user *, oact)
{
struct k_sigaction new_ka, old_ka;
int ret;
if (act) {
old_sigset_t mask;
if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
__get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
__get_user(new_ka.sa.sa_restorer, &act->sa_restorer) ||
__get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
__get_user(mask, &act->sa_mask))
return -EFAULT;
#ifdef __ARCH_HAS_KA_RESTORER
new_ka.ka_restorer = NULL;
#endif
siginitset(&new_ka.sa.sa_mask, mask);
}
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
__put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
__put_user(old_ka.sa.sa_restorer, &oact->sa_restorer) ||
__put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
__put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
return -EFAULT;
}
return ret;
}
#endif
#ifdef CONFIG_COMPAT_OLD_SIGACTION
COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
const struct compat_old_sigaction __user *, act,
struct compat_old_sigaction __user *, oact)
{
struct k_sigaction new_ka, old_ka;
int ret;
compat_old_sigset_t mask;
compat_uptr_t handler, restorer;
if (act) {
if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
__get_user(handler, &act->sa_handler) ||
__get_user(restorer, &act->sa_restorer) ||
__get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
__get_user(mask, &act->sa_mask))
return -EFAULT;
#ifdef __ARCH_HAS_KA_RESTORER
new_ka.ka_restorer = NULL;
#endif
new_ka.sa.sa_handler = compat_ptr(handler);
new_ka.sa.sa_restorer = compat_ptr(restorer);
siginitset(&new_ka.sa.sa_mask, mask);
}
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
__put_user(ptr_to_compat(old_ka.sa.sa_handler),
&oact->sa_handler) ||
__put_user(ptr_to_compat(old_ka.sa.sa_restorer),
&oact->sa_restorer) ||
__put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
__put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
return -EFAULT;
}
return ret;
}
#endif
#ifdef CONFIG_SGETMASK_SYSCALL
/*
* For backwards compatibility. Functionality superseded by sigprocmask.
*/
SYSCALL_DEFINE0(sgetmask)
{
/* SMP safe */
return current->blocked.sig[0];
}
SYSCALL_DEFINE1(ssetmask, int, newmask)
{
int old = current->blocked.sig[0];
sigset_t newset;
siginitset(&newset, newmask);
set_current_blocked(&newset);
return old;
}
#endif /* CONFIG_SGETMASK_SYSCALL */
#ifdef __ARCH_WANT_SYS_SIGNAL
/*
* For backwards compatibility. Functionality superseded by sigaction.
*/
SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
{
struct k_sigaction new_sa, old_sa;
int ret;
new_sa.sa.sa_handler = handler;
new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK;
sigemptyset(&new_sa.sa.sa_mask);
ret = do_sigaction(sig, &new_sa, &old_sa);
return ret ? ret : (unsigned long)old_sa.sa.sa_handler;
}
#endif /* __ARCH_WANT_SYS_SIGNAL */
#ifdef __ARCH_WANT_SYS_PAUSE
SYSCALL_DEFINE0(pause)
{
while (!signal_pending(current)) {
__set_current_state(TASK_INTERRUPTIBLE);
schedule();
}
return -ERESTARTNOHAND;
}
#endif
static int sigsuspend(sigset_t *set)
{
current->saved_sigmask = current->blocked;
set_current_blocked(set);
while (!signal_pending(current)) {
__set_current_state(TASK_INTERRUPTIBLE);
schedule();
}
set_restore_sigmask();
return -ERESTARTNOHAND;
}
/**
* sys_rt_sigsuspend - replace the signal mask for a value with the
* @unewset value until a signal is received
* @unewset: new signal mask value
* @sigsetsize: size of sigset_t type
*/
SYSCALL_DEFINE2(rt_sigsuspend, sigset_t __user *, unewset, size_t, sigsetsize)
{
sigset_t newset;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
if (copy_from_user(&newset, unewset, sizeof(newset)))
return -EFAULT;
return sigsuspend(&newset);
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(rt_sigsuspend, compat_sigset_t __user *, unewset, compat_size_t, sigsetsize)
{
sigset_t newset;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
if (get_compat_sigset(&newset, unewset))
return -EFAULT;
return sigsuspend(&newset);
}
#endif
#ifdef CONFIG_OLD_SIGSUSPEND
SYSCALL_DEFINE1(sigsuspend, old_sigset_t, mask)
{
sigset_t blocked;
siginitset(&blocked, mask);
return sigsuspend(&blocked);
}
#endif
#ifdef CONFIG_OLD_SIGSUSPEND3
SYSCALL_DEFINE3(sigsuspend, int, unused1, int, unused2, old_sigset_t, mask)
{
sigset_t blocked;
siginitset(&blocked, mask);
return sigsuspend(&blocked);
}
#endif
__weak const char *arch_vma_name(struct vm_area_struct *vma)
{
return NULL;
}
void __init signals_init(void)
{
kernel/signal.c: add compile-time check for __ARCH_SI_PREAMBLE_SIZE The value of __ARCH_SI_PREAMBLE_SIZE defines the size (including padding) of the part of the struct siginfo that is before the union, and it is then used to calculate the needed padding (SI_PAD_SIZE) to make the size of struct siginfo equal to 128 (SI_MAX_SIZE) bytes. Depending on the target architecture and word width it equals to either 3 or 4 times sizeof int. Since the very beginning we had __ARCH_SI_PREAMBLE_SIZE wrong on the parisc architecture for the 64bit kernel build. It's even more frustrating, because it can easily be checked at compile time if the value was defined correctly. This patch adds such a check for the correctness of __ARCH_SI_PREAMBLE_SIZE in the hope that it will prevent existing and future architectures from running into the same problem. I refrained from replacing __ARCH_SI_PREAMBLE_SIZE by offsetof() in copy_siginfo() in include/asm-generic/siginfo.h, because a) it doesn't make any difference and b) it's used in the Documentation/kmemcheck.txt example. I ran this patch through the 0-DAY kernel test infrastructure and only the parisc architecture triggered as expected. That means that this patch should be OK for all major architectures. Signed-off-by: Helge Deller <deller@gmx.de> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-22 21:27:54 +00:00
/* If this check fails, the __ARCH_SI_PREAMBLE_SIZE value is wrong! */
BUILD_BUG_ON(__ARCH_SI_PREAMBLE_SIZE
!= offsetof(struct siginfo, _sifields._pad));
BUILD_BUG_ON(sizeof(struct siginfo) != SI_MAX_SIZE);
kernel/signal.c: add compile-time check for __ARCH_SI_PREAMBLE_SIZE The value of __ARCH_SI_PREAMBLE_SIZE defines the size (including padding) of the part of the struct siginfo that is before the union, and it is then used to calculate the needed padding (SI_PAD_SIZE) to make the size of struct siginfo equal to 128 (SI_MAX_SIZE) bytes. Depending on the target architecture and word width it equals to either 3 or 4 times sizeof int. Since the very beginning we had __ARCH_SI_PREAMBLE_SIZE wrong on the parisc architecture for the 64bit kernel build. It's even more frustrating, because it can easily be checked at compile time if the value was defined correctly. This patch adds such a check for the correctness of __ARCH_SI_PREAMBLE_SIZE in the hope that it will prevent existing and future architectures from running into the same problem. I refrained from replacing __ARCH_SI_PREAMBLE_SIZE by offsetof() in copy_siginfo() in include/asm-generic/siginfo.h, because a) it doesn't make any difference and b) it's used in the Documentation/kmemcheck.txt example. I ran this patch through the 0-DAY kernel test infrastructure and only the parisc architecture triggered as expected. That means that this patch should be OK for all major architectures. Signed-off-by: Helge Deller <deller@gmx.de> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-22 21:27:54 +00:00
sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
}
#ifdef CONFIG_KGDB_KDB
#include <linux/kdb.h>
/*
* kdb_send_sig - Allows kdb to send signals without exposing
* signal internals. This function checks if the required locks are
* available before calling the main signal code, to avoid kdb
* deadlocks.
*/
void kdb_send_sig(struct task_struct *t, int sig)
{
static struct task_struct *kdb_prev_t;
int new_t, ret;
if (!spin_trylock(&t->sighand->siglock)) {
kdb_printf("Can't do kill command now.\n"
"The sigmask lock is held somewhere else in "
"kernel, try again later\n");
return;
}
new_t = kdb_prev_t != t;
kdb_prev_t = t;
if (t->state != TASK_RUNNING && new_t) {
spin_unlock(&t->sighand->siglock);
kdb_printf("Process is not RUNNING, sending a signal from "
"kdb risks deadlock\n"
"on the run queue locks. "
"The signal has _not_ been sent.\n"
"Reissue the kill command if you want to risk "
"the deadlock.\n");
return;
}
ret = send_signal(sig, SEND_SIG_PRIV, t, false);
spin_unlock(&t->sighand->siglock);
if (ret)
kdb_printf("Fail to deliver Signal %d to process %d.\n",
sig, t->pid);
else
kdb_printf("Signal %d is sent to process %d.\n", sig, t->pid);
}
#endif /* CONFIG_KGDB_KDB */