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Oleg Nesterov 3245d6acab exit: fix race between wait_consider_task() and wait_task_zombie() 
wait_consider_task() checks EXIT_ZOMBIE after EXIT_DEAD/EXIT_TRACE and
both checks can fail if we race with EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE
change in between, gcc needs to reload p->exit_state after
security_task_wait().  In this case ->notask_error will be wrongly
cleared and do_wait() can hang forever if it was the last eligible
child.

Many thanks to Arne who carefully investigated the problem.

Note: this bug is very old but it was pure theoretical until commit
b3ab03160d ("wait: completely ignore the EXIT_DEAD tasks").  Before
this commit "-O2" was probably enough to guarantee that compiler won't
read ->exit_state twice.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Arne Goedeke <el@laramies.com>
Tested-by: Arne Goedeke <el@laramies.com>
Cc: <stable@vger.kernel.org>	[3.15+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-01-08 15:10:51 -08:00
..
bpf bpf: verifier: add checks for BPF_ABS | BPF_IND instructions 2014-12-05 21:47:32 -08:00
configs x86: Add "make tinyconfig" to configure the tiniest possible kernel 2014-08-08 16:30:24 -07:00
debug kdb: replace strnicmp with strncasecmp 2014-10-14 02:18:25 +02:00
events Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-19 13:15:24 -08:00
gcov gcov: enable GCOV_PROFILE_ALL from ARCH Kconfigs 2014-12-13 12:42:51 -08:00
irq genirq: Prevent proc race against freeing of irq descriptors 2014-12-13 13:33:07 +01:00
locking locking/mutex: Don't assume TASK_RUNNING 2014-10-28 10:55:08 +01:00
power PM: Eliminate CONFIG_PM_RUNTIME 2014-12-19 22:55:06 +01:00
printk This code is a fork from the trace-3.19 pull as it needed the trace_seq 2014-12-13 14:04:41 -08:00
rcu Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', 'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD 2014-11-13 10:39:04 -08:00
sched sched_show_task: fix unsafe usage of ->real_parent 2014-12-10 17:41:09 -08:00
time Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-19 13:29:20 -08:00
trace More ACPI and power management updates for 3.19-rc1 2014-12-18 20:28:33 -08:00
.gitignore
acct.c acct: eliminate compile warning 2014-10-09 22:26:04 -04:00
async.c kernel/async.c: switch to pr_foo() 2014-10-09 22:26:04 -04:00
audit.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-12-30 10:45:47 -08:00
audit.h audit: reduce scope of audit_log_fcaps 2014-09-23 16:37:51 -04:00
audit_tree.c fsnotify: unify inode and mount marks handling 2014-12-13 12:42:53 -08:00
audit_watch.c audit: invalid op= values for rules 2014-09-23 16:37:53 -04:00
auditfilter.c Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit 2014-12-23 18:13:16 -08:00
auditsc.c Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit 2014-12-31 14:52:18 -08:00
backtracetest.c kernel/backtracetest.c: replace no level printk by pr_info() 2014-06-04 16:54:14 -07:00
bounds.c page-cgroup: get rid of NR_PCG_FLAGS 2014-08-08 15:57:18 -07:00
capability.c CAPABILITIES: remove undefined caps from all processes 2014-07-24 21:53:47 +10:00
cgroup.c cgroup: implement cgroup_get_e_css() 2014-11-18 02:49:52 -05:00
cgroup_freezer.c cgroup: rename cgroup_subsys->base_cftypes to ->legacy_cftypes 2014-07-15 11:05:09 -04:00
compat.c compat: nanosleep: Clarify error handling 2014-09-06 12:58:18 +02:00
configs.c
context_tracking.c sched: stop the unbound recursion in preempt_schedule_context() 2014-10-28 10:46:05 +01:00
cpu.c cpu: Avoid puts_pending overflow 2014-11-03 19:21:01 -08:00
cpu_pm.c
cpuset.c Merge branch 'for-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2014-12-11 18:57:19 -08:00
crash_dump.c crash_dump: Make is_kdump_kernel() accessible from modules 2014-08-25 15:42:19 -07:00
cred.c
delayacct.c delayacct: Remove braindamaged type conversions 2014-07-23 10:18:06 -07:00
dma.c
elfcore.c
exec_domain.c kernel/exec_domain.c: code clean-up 2014-06-04 16:54:15 -07:00
exit.c exit: fix race between wait_consider_task() and wait_task_zombie() 2015-01-08 15:10:51 -08:00
extable.c ftrace/x86/extable: Add is_ftrace_trampoline() function 2014-11-19 15:25:26 -05:00
fork.c mm: use new helper functions around the i_mmap_mutex 2014-12-13 12:42:45 -08:00
freezer.c freezer: remove obsolete comments in __thaw_task() 2014-10-21 23:44:20 +02:00
futex.c futex: Fix a race condition between REQUEUE_PI and task death 2014-10-26 16:16:18 +01:00
futex_compat.c
groups.c userns: Don't allow setgroups until a gid mapping has been setablished 2014-12-09 16:58:40 -06:00
hung_task.c kernel/hung_task.c: convert simple_strtoul to kstrtouint 2014-06-04 16:54:15 -07:00
irq_work.c percpu: Convert remaining __get_cpu_var uses in 3.18-rcX 2014-10-29 11:18:18 -04:00
jump_label.c
kallsyms.c kernel/kallsyms.c: use __seq_open_private() 2014-10-14 02:18:16 +02:00
kcmp.c kcmp: fix standard comparison bug 2014-09-10 15:42:12 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER 2014-07-16 14:57:13 +02:00
Kconfig.preempt
kexec.c kexec: remove unnecessary KERN_ERR from kexec.c 2014-12-13 12:42:51 -08:00
kmod.c usermodehelper: kill the kmod_thread_locker logic 2014-12-10 17:41:17 -08:00
kprobes.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2014-12-11 17:30:55 -08:00
ksysfs.c
kthread.c kernel/kthread.c: partial revert of 81c98869fa ("kthread: ensure locality of task_struct allocations") 2014-10-09 22:25:51 -04:00
latencytop.c kernel/latencytop.c: convert seq_printf to seq_puts 2014-06-04 16:54:15 -07:00
Makefile kernel: res_counter: remove the unused API 2014-12-10 17:41:04 -08:00
module-internal.h
module.c The exciting thing here is the getting rid of stop_machine on module 2014-12-18 20:55:41 -08:00
module_signing.c
notifier.c
nsproxy.c bury struct proc_ns in fs/proc 2014-12-04 14:34:54 -05:00
padata.c
panic.c kernel: add panic_on_warn 2014-12-10 17:41:10 -08:00
params.c param: do not set store func without write perm 2014-12-18 12:38:51 +10:30
pid.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-12-16 15:53:03 -08:00
pid_namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-12-16 15:53:03 -08:00
profile.c kernel/profile.c: use static const char instead of static char 2014-06-06 16:08:13 -07:00
ptrace.c exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent() 2014-12-10 17:41:10 -08:00
range.c
reboot.c kernel: add support for kernel restart handler call chain 2014-09-26 00:00:06 -07:00
relay.c
resource.c x86: optimize resource lookups for ioremap 2014-10-14 02:18:22 +02:00
seccomp.c Merge branch 'x86-seccomp-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-10-14 02:27:06 +02:00
signal.c Merge branch 'x86-mpx-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-10 09:34:43 -08:00
smp.c Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-15 07:48:18 +02:00
smpboot.c sched, smp: Correctly deal with nested sleeps 2014-10-28 10:56:24 +01:00
smpboot.h
softirq.c rcu: Remove "cpu" argument to rcu_note_context_switch() 2014-11-03 19:20:34 -08:00
stacktrace.c stacktrace: introduce snprint_stack_trace for buffer output 2014-12-13 12:42:48 -08:00
stop_machine.c kernel/stop_machine.c: kernel-doc warning fix 2014-06-04 16:54:15 -07:00
sys.c x86, mpx: On-demand kernel allocation of bounds tables 2014-11-18 00:58:53 +01:00
sys_ni.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
sysctl.c As the merge window is still open, and this code was not as complex 2014-12-16 12:53:59 -08:00
sysctl_binary.c kernel: add panic_on_warn 2014-12-10 17:41:10 -08:00
system_certificates.S
system_keyring.c KEYS: validate certificate trust only with builtin keys 2014-07-17 09:35:17 -04:00
task_work.c
taskstats.c kill f_dentry uses 2014-11-19 13:01:25 -05:00
test_kprobes.c kernel/test_kprobes.c: use current logging functions 2014-08-08 15:57:18 -07:00
torture.c torture: Address race in module cleanup 2014-09-16 13:41:06 -07:00
tracepoint.c tracing: syscall_regfunc() should not skip kernel threads 2014-06-21 00:15:26 -04:00
tsacct.c sched: Make task->start_time nanoseconds based 2014-07-23 10:18:05 -07:00
uid16.c groups: Consolidate the setgroups permission checks 2014-12-05 17:19:27 -06:00
up.c
user-return-notifier.c scheduler: Replace __get_cpu_var with this_cpu_ptr 2014-08-26 13:45:45 -04:00
user.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2014-12-17 12:31:40 -08:00
user_namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2014-12-17 12:31:40 -08:00
utsname.c copy address of proc_ns_ops into ns_common 2014-12-04 14:34:47 -05:00
utsname_sysctl.c sysctl: convert use of typedef ctl_table to struct ctl_table 2014-06-06 16:08:16 -07:00
watchdog.c Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-15 07:48:18 +02:00
workqueue.c workqueue: allow rescuer thread to do more work. 2014-12-08 12:39:16 -05:00
workqueue_internal.h workqueue: rename manager_mutex to attach_mutex 2014-05-20 10:59:32 -04:00