linux/ipc/msg.c
Davidlohr Bueso 23c8cec8cf ipc/msg: introduce msgctl(MSG_STAT_ANY)
There is a permission discrepancy when consulting msq ipc object
metadata between /proc/sysvipc/msg (0444) and the MSG_STAT shmctl
command.  The later does permission checks for the object vs S_IRUGO.
As such there can be cases where EACCESS is returned via syscall but the
info is displayed anyways in the procfs files.

While this might have security implications via info leaking (albeit no
writing to the msq metadata), this behavior goes way back and showing
all the objects regardless of the permissions was most likely an
overlook - so we are stuck with it.  Furthermore, modifying either the
syscall or the procfs file can cause userspace programs to break (ie
ipcs).  Some applications require getting the procfs info (without root
privileges) and can be rather slow in comparison with a syscall -- up to
500x in some reported cases for shm.

This patch introduces a new MSG_STAT_ANY command such that the msq ipc
object permissions are ignored, and only audited instead.  In addition,
I've left the lsm security hook checks in place, as if some policy can
block the call, then the user has no other choice than just parsing the
procfs file.

Link: http://lkml.kernel.org/r/20180215162458.10059-4-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reported-by: Robert Kettler <robert.kettler@outlook.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-11 10:28:37 -07:00

1281 lines
29 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* linux/ipc/msg.c
* Copyright (C) 1992 Krishna Balasubramanian
*
* Removed all the remaining kerneld mess
* Catch the -EFAULT stuff properly
* Use GFP_KERNEL for messages as in 1.2
* Fixed up the unchecked user space derefs
* Copyright (C) 1998 Alan Cox & Andi Kleen
*
* /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
*
* mostly rewritten, threaded and wake-one semantics added
* MSGMAX limit removed, sysctl's added
* (c) 1999 Manfred Spraul <manfred@colorfullife.com>
*
* support for audit of ipc object properties and permission changes
* Dustin Kirkland <dustin.kirkland@us.ibm.com>
*
* namespaces support
* OpenVZ, SWsoft Inc.
* Pavel Emelianov <xemul@openvz.org>
*/
#include <linux/capability.h>
#include <linux/msg.h>
#include <linux/spinlock.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/list.h>
#include <linux/security.h>
#include <linux/sched/wake_q.h>
#include <linux/syscalls.h>
#include <linux/audit.h>
#include <linux/seq_file.h>
#include <linux/rwsem.h>
#include <linux/nsproxy.h>
#include <linux/ipc_namespace.h>
#include <asm/current.h>
#include <linux/uaccess.h>
#include "util.h"
/* one msq_queue structure for each present queue on the system */
struct msg_queue {
struct kern_ipc_perm q_perm;
time64_t q_stime; /* last msgsnd time */
time64_t q_rtime; /* last msgrcv time */
time64_t q_ctime; /* last change time */
unsigned long q_cbytes; /* current number of bytes on queue */
unsigned long q_qnum; /* number of messages in queue */
unsigned long q_qbytes; /* max number of bytes on queue */
struct pid *q_lspid; /* pid of last msgsnd */
struct pid *q_lrpid; /* last receive pid */
struct list_head q_messages;
struct list_head q_receivers;
struct list_head q_senders;
} __randomize_layout;
/* one msg_receiver structure for each sleeping receiver */
struct msg_receiver {
struct list_head r_list;
struct task_struct *r_tsk;
int r_mode;
long r_msgtype;
long r_maxsize;
struct msg_msg *r_msg;
};
/* one msg_sender for each sleeping sender */
struct msg_sender {
struct list_head list;
struct task_struct *tsk;
size_t msgsz;
};
#define SEARCH_ANY 1
#define SEARCH_EQUAL 2
#define SEARCH_NOTEQUAL 3
#define SEARCH_LESSEQUAL 4
#define SEARCH_NUMBER 5
#define msg_ids(ns) ((ns)->ids[IPC_MSG_IDS])
static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
{
struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&msg_ids(ns), id);
if (IS_ERR(ipcp))
return ERR_CAST(ipcp);
return container_of(ipcp, struct msg_queue, q_perm);
}
static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns,
int id)
{
struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id);
if (IS_ERR(ipcp))
return ERR_CAST(ipcp);
return container_of(ipcp, struct msg_queue, q_perm);
}
static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
{
ipc_rmid(&msg_ids(ns), &s->q_perm);
}
static void msg_rcu_free(struct rcu_head *head)
{
struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
struct msg_queue *msq = container_of(p, struct msg_queue, q_perm);
security_msg_queue_free(&msq->q_perm);
kvfree(msq);
}
/**
* newque - Create a new msg queue
* @ns: namespace
* @params: ptr to the structure that contains the key and msgflg
*
* Called with msg_ids.rwsem held (writer)
*/
static int newque(struct ipc_namespace *ns, struct ipc_params *params)
{
struct msg_queue *msq;
int retval;
key_t key = params->key;
int msgflg = params->flg;
msq = kvmalloc(sizeof(*msq), GFP_KERNEL);
if (unlikely(!msq))
return -ENOMEM;
msq->q_perm.mode = msgflg & S_IRWXUGO;
msq->q_perm.key = key;
msq->q_perm.security = NULL;
retval = security_msg_queue_alloc(&msq->q_perm);
if (retval) {
kvfree(msq);
return retval;
}
msq->q_stime = msq->q_rtime = 0;
msq->q_ctime = ktime_get_real_seconds();
msq->q_cbytes = msq->q_qnum = 0;
msq->q_qbytes = ns->msg_ctlmnb;
msq->q_lspid = msq->q_lrpid = NULL;
INIT_LIST_HEAD(&msq->q_messages);
INIT_LIST_HEAD(&msq->q_receivers);
INIT_LIST_HEAD(&msq->q_senders);
/* ipc_addid() locks msq upon success. */
retval = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
if (retval < 0) {
call_rcu(&msq->q_perm.rcu, msg_rcu_free);
return retval;
}
ipc_unlock_object(&msq->q_perm);
rcu_read_unlock();
return msq->q_perm.id;
}
static inline bool msg_fits_inqueue(struct msg_queue *msq, size_t msgsz)
{
return msgsz + msq->q_cbytes <= msq->q_qbytes &&
1 + msq->q_qnum <= msq->q_qbytes;
}
static inline void ss_add(struct msg_queue *msq,
struct msg_sender *mss, size_t msgsz)
{
mss->tsk = current;
mss->msgsz = msgsz;
__set_current_state(TASK_INTERRUPTIBLE);
list_add_tail(&mss->list, &msq->q_senders);
}
static inline void ss_del(struct msg_sender *mss)
{
if (mss->list.next)
list_del(&mss->list);
}
static void ss_wakeup(struct msg_queue *msq,
struct wake_q_head *wake_q, bool kill)
{
struct msg_sender *mss, *t;
struct task_struct *stop_tsk = NULL;
struct list_head *h = &msq->q_senders;
list_for_each_entry_safe(mss, t, h, list) {
if (kill)
mss->list.next = NULL;
/*
* Stop at the first task we don't wakeup,
* we've already iterated the original
* sender queue.
*/
else if (stop_tsk == mss->tsk)
break;
/*
* We are not in an EIDRM scenario here, therefore
* verify that we really need to wakeup the task.
* To maintain current semantics and wakeup order,
* move the sender to the tail on behalf of the
* blocked task.
*/
else if (!msg_fits_inqueue(msq, mss->msgsz)) {
if (!stop_tsk)
stop_tsk = mss->tsk;
list_move_tail(&mss->list, &msq->q_senders);
continue;
}
wake_q_add(wake_q, mss->tsk);
}
}
static void expunge_all(struct msg_queue *msq, int res,
struct wake_q_head *wake_q)
{
struct msg_receiver *msr, *t;
list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
wake_q_add(wake_q, msr->r_tsk);
WRITE_ONCE(msr->r_msg, ERR_PTR(res));
}
}
/*
* freeque() wakes up waiters on the sender and receiver waiting queue,
* removes the message queue from message queue ID IDR, and cleans up all the
* messages associated with this queue.
*
* msg_ids.rwsem (writer) and the spinlock for this message queue are held
* before freeque() is called. msg_ids.rwsem remains locked on exit.
*/
static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
{
struct msg_msg *msg, *t;
struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
DEFINE_WAKE_Q(wake_q);
expunge_all(msq, -EIDRM, &wake_q);
ss_wakeup(msq, &wake_q, true);
msg_rmid(ns, msq);
ipc_unlock_object(&msq->q_perm);
wake_up_q(&wake_q);
rcu_read_unlock();
list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
atomic_dec(&ns->msg_hdrs);
free_msg(msg);
}
atomic_sub(msq->q_cbytes, &ns->msg_bytes);
ipc_update_pid(&msq->q_lspid, NULL);
ipc_update_pid(&msq->q_lrpid, NULL);
ipc_rcu_putref(&msq->q_perm, msg_rcu_free);
}
long ksys_msgget(key_t key, int msgflg)
{
struct ipc_namespace *ns;
static const struct ipc_ops msg_ops = {
.getnew = newque,
.associate = security_msg_queue_associate,
};
struct ipc_params msg_params;
ns = current->nsproxy->ipc_ns;
msg_params.key = key;
msg_params.flg = msgflg;
return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
}
SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
{
return ksys_msgget(key, msgflg);
}
static inline unsigned long
copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
{
switch (version) {
case IPC_64:
return copy_to_user(buf, in, sizeof(*in));
case IPC_OLD:
{
struct msqid_ds out;
memset(&out, 0, sizeof(out));
ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
out.msg_stime = in->msg_stime;
out.msg_rtime = in->msg_rtime;
out.msg_ctime = in->msg_ctime;
if (in->msg_cbytes > USHRT_MAX)
out.msg_cbytes = USHRT_MAX;
else
out.msg_cbytes = in->msg_cbytes;
out.msg_lcbytes = in->msg_cbytes;
if (in->msg_qnum > USHRT_MAX)
out.msg_qnum = USHRT_MAX;
else
out.msg_qnum = in->msg_qnum;
if (in->msg_qbytes > USHRT_MAX)
out.msg_qbytes = USHRT_MAX;
else
out.msg_qbytes = in->msg_qbytes;
out.msg_lqbytes = in->msg_qbytes;
out.msg_lspid = in->msg_lspid;
out.msg_lrpid = in->msg_lrpid;
return copy_to_user(buf, &out, sizeof(out));
}
default:
return -EINVAL;
}
}
static inline unsigned long
copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
{
switch (version) {
case IPC_64:
if (copy_from_user(out, buf, sizeof(*out)))
return -EFAULT;
return 0;
case IPC_OLD:
{
struct msqid_ds tbuf_old;
if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
return -EFAULT;
out->msg_perm.uid = tbuf_old.msg_perm.uid;
out->msg_perm.gid = tbuf_old.msg_perm.gid;
out->msg_perm.mode = tbuf_old.msg_perm.mode;
if (tbuf_old.msg_qbytes == 0)
out->msg_qbytes = tbuf_old.msg_lqbytes;
else
out->msg_qbytes = tbuf_old.msg_qbytes;
return 0;
}
default:
return -EINVAL;
}
}
/*
* This function handles some msgctl commands which require the rwsem
* to be held in write mode.
* NOTE: no locks must be held, the rwsem is taken inside this function.
*/
static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
struct msqid64_ds *msqid64)
{
struct kern_ipc_perm *ipcp;
struct msg_queue *msq;
int err;
down_write(&msg_ids(ns).rwsem);
rcu_read_lock();
ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
&msqid64->msg_perm, msqid64->msg_qbytes);
if (IS_ERR(ipcp)) {
err = PTR_ERR(ipcp);
goto out_unlock1;
}
msq = container_of(ipcp, struct msg_queue, q_perm);
err = security_msg_queue_msgctl(&msq->q_perm, cmd);
if (err)
goto out_unlock1;
switch (cmd) {
case IPC_RMID:
ipc_lock_object(&msq->q_perm);
/* freeque unlocks the ipc object and rcu */
freeque(ns, ipcp);
goto out_up;
case IPC_SET:
{
DEFINE_WAKE_Q(wake_q);
if (msqid64->msg_qbytes > ns->msg_ctlmnb &&
!capable(CAP_SYS_RESOURCE)) {
err = -EPERM;
goto out_unlock1;
}
ipc_lock_object(&msq->q_perm);
err = ipc_update_perm(&msqid64->msg_perm, ipcp);
if (err)
goto out_unlock0;
msq->q_qbytes = msqid64->msg_qbytes;
msq->q_ctime = ktime_get_real_seconds();
/*
* Sleeping receivers might be excluded by
* stricter permissions.
*/
expunge_all(msq, -EAGAIN, &wake_q);
/*
* Sleeping senders might be able to send
* due to a larger queue size.
*/
ss_wakeup(msq, &wake_q, false);
ipc_unlock_object(&msq->q_perm);
wake_up_q(&wake_q);
goto out_unlock1;
}
default:
err = -EINVAL;
goto out_unlock1;
}
out_unlock0:
ipc_unlock_object(&msq->q_perm);
out_unlock1:
rcu_read_unlock();
out_up:
up_write(&msg_ids(ns).rwsem);
return err;
}
static int msgctl_info(struct ipc_namespace *ns, int msqid,
int cmd, struct msginfo *msginfo)
{
int err;
int max_id;
/*
* We must not return kernel stack data.
* due to padding, it's not enough
* to set all member fields.
*/
err = security_msg_queue_msgctl(NULL, cmd);
if (err)
return err;
memset(msginfo, 0, sizeof(*msginfo));
msginfo->msgmni = ns->msg_ctlmni;
msginfo->msgmax = ns->msg_ctlmax;
msginfo->msgmnb = ns->msg_ctlmnb;
msginfo->msgssz = MSGSSZ;
msginfo->msgseg = MSGSEG;
down_read(&msg_ids(ns).rwsem);
if (cmd == MSG_INFO) {
msginfo->msgpool = msg_ids(ns).in_use;
msginfo->msgmap = atomic_read(&ns->msg_hdrs);
msginfo->msgtql = atomic_read(&ns->msg_bytes);
} else {
msginfo->msgmap = MSGMAP;
msginfo->msgpool = MSGPOOL;
msginfo->msgtql = MSGTQL;
}
max_id = ipc_get_maxid(&msg_ids(ns));
up_read(&msg_ids(ns).rwsem);
return (max_id < 0) ? 0 : max_id;
}
static int msgctl_stat(struct ipc_namespace *ns, int msqid,
int cmd, struct msqid64_ds *p)
{
struct msg_queue *msq;
int id = 0;
int err;
memset(p, 0, sizeof(*p));
rcu_read_lock();
if (cmd == MSG_STAT || cmd == MSG_STAT_ANY) {
msq = msq_obtain_object(ns, msqid);
if (IS_ERR(msq)) {
err = PTR_ERR(msq);
goto out_unlock;
}
id = msq->q_perm.id;
} else { /* IPC_STAT */
msq = msq_obtain_object_check(ns, msqid);
if (IS_ERR(msq)) {
err = PTR_ERR(msq);
goto out_unlock;
}
}
/* see comment for SHM_STAT_ANY */
if (cmd == MSG_STAT_ANY)
audit_ipc_obj(&msq->q_perm);
else {
err = -EACCES;
if (ipcperms(ns, &msq->q_perm, S_IRUGO))
goto out_unlock;
}
err = security_msg_queue_msgctl(&msq->q_perm, cmd);
if (err)
goto out_unlock;
ipc_lock_object(&msq->q_perm);
if (!ipc_valid_object(&msq->q_perm)) {
ipc_unlock_object(&msq->q_perm);
err = -EIDRM;
goto out_unlock;
}
kernel_to_ipc64_perm(&msq->q_perm, &p->msg_perm);
p->msg_stime = msq->q_stime;
p->msg_rtime = msq->q_rtime;
p->msg_ctime = msq->q_ctime;
p->msg_cbytes = msq->q_cbytes;
p->msg_qnum = msq->q_qnum;
p->msg_qbytes = msq->q_qbytes;
p->msg_lspid = pid_vnr(msq->q_lspid);
p->msg_lrpid = pid_vnr(msq->q_lrpid);
ipc_unlock_object(&msq->q_perm);
rcu_read_unlock();
return id;
out_unlock:
rcu_read_unlock();
return err;
}
long ksys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
{
int version;
struct ipc_namespace *ns;
struct msqid64_ds msqid64;
int err;
if (msqid < 0 || cmd < 0)
return -EINVAL;
version = ipc_parse_version(&cmd);
ns = current->nsproxy->ipc_ns;
switch (cmd) {
case IPC_INFO:
case MSG_INFO: {
struct msginfo msginfo;
err = msgctl_info(ns, msqid, cmd, &msginfo);
if (err < 0)
return err;
if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
err = -EFAULT;
return err;
}
case MSG_STAT: /* msqid is an index rather than a msg queue id */
case MSG_STAT_ANY:
case IPC_STAT:
err = msgctl_stat(ns, msqid, cmd, &msqid64);
if (err < 0)
return err;
if (copy_msqid_to_user(buf, &msqid64, version))
err = -EFAULT;
return err;
case IPC_SET:
if (copy_msqid_from_user(&msqid64, buf, version))
return -EFAULT;
/* fallthru */
case IPC_RMID:
return msgctl_down(ns, msqid, cmd, &msqid64);
default:
return -EINVAL;
}
}
SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
{
return ksys_msgctl(msqid, cmd, buf);
}
#ifdef CONFIG_COMPAT
struct compat_msqid_ds {
struct compat_ipc_perm msg_perm;
compat_uptr_t msg_first;
compat_uptr_t msg_last;
compat_time_t msg_stime;
compat_time_t msg_rtime;
compat_time_t msg_ctime;
compat_ulong_t msg_lcbytes;
compat_ulong_t msg_lqbytes;
unsigned short msg_cbytes;
unsigned short msg_qnum;
unsigned short msg_qbytes;
compat_ipc_pid_t msg_lspid;
compat_ipc_pid_t msg_lrpid;
};
static int copy_compat_msqid_from_user(struct msqid64_ds *out, void __user *buf,
int version)
{
memset(out, 0, sizeof(*out));
if (version == IPC_64) {
struct compat_msqid64_ds __user *p = buf;
if (get_compat_ipc64_perm(&out->msg_perm, &p->msg_perm))
return -EFAULT;
if (get_user(out->msg_qbytes, &p->msg_qbytes))
return -EFAULT;
} else {
struct compat_msqid_ds __user *p = buf;
if (get_compat_ipc_perm(&out->msg_perm, &p->msg_perm))
return -EFAULT;
if (get_user(out->msg_qbytes, &p->msg_qbytes))
return -EFAULT;
}
return 0;
}
static int copy_compat_msqid_to_user(void __user *buf, struct msqid64_ds *in,
int version)
{
if (version == IPC_64) {
struct compat_msqid64_ds v;
memset(&v, 0, sizeof(v));
to_compat_ipc64_perm(&v.msg_perm, &in->msg_perm);
v.msg_stime = in->msg_stime;
v.msg_rtime = in->msg_rtime;
v.msg_ctime = in->msg_ctime;
v.msg_cbytes = in->msg_cbytes;
v.msg_qnum = in->msg_qnum;
v.msg_qbytes = in->msg_qbytes;
v.msg_lspid = in->msg_lspid;
v.msg_lrpid = in->msg_lrpid;
return copy_to_user(buf, &v, sizeof(v));
} else {
struct compat_msqid_ds v;
memset(&v, 0, sizeof(v));
to_compat_ipc_perm(&v.msg_perm, &in->msg_perm);
v.msg_stime = in->msg_stime;
v.msg_rtime = in->msg_rtime;
v.msg_ctime = in->msg_ctime;
v.msg_cbytes = in->msg_cbytes;
v.msg_qnum = in->msg_qnum;
v.msg_qbytes = in->msg_qbytes;
v.msg_lspid = in->msg_lspid;
v.msg_lrpid = in->msg_lrpid;
return copy_to_user(buf, &v, sizeof(v));
}
}
long compat_ksys_msgctl(int msqid, int cmd, void __user *uptr)
{
struct ipc_namespace *ns;
int err;
struct msqid64_ds msqid64;
int version = compat_ipc_parse_version(&cmd);
ns = current->nsproxy->ipc_ns;
if (msqid < 0 || cmd < 0)
return -EINVAL;
switch (cmd & (~IPC_64)) {
case IPC_INFO:
case MSG_INFO: {
struct msginfo msginfo;
err = msgctl_info(ns, msqid, cmd, &msginfo);
if (err < 0)
return err;
if (copy_to_user(uptr, &msginfo, sizeof(struct msginfo)))
err = -EFAULT;
return err;
}
case IPC_STAT:
case MSG_STAT:
case MSG_STAT_ANY:
err = msgctl_stat(ns, msqid, cmd, &msqid64);
if (err < 0)
return err;
if (copy_compat_msqid_to_user(uptr, &msqid64, version))
err = -EFAULT;
return err;
case IPC_SET:
if (copy_compat_msqid_from_user(&msqid64, uptr, version))
return -EFAULT;
/* fallthru */
case IPC_RMID:
return msgctl_down(ns, msqid, cmd, &msqid64);
default:
return -EINVAL;
}
}
COMPAT_SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, void __user *, uptr)
{
return compat_ksys_msgctl(msqid, cmd, uptr);
}
#endif
static int testmsg(struct msg_msg *msg, long type, int mode)
{
switch (mode) {
case SEARCH_ANY:
case SEARCH_NUMBER:
return 1;
case SEARCH_LESSEQUAL:
if (msg->m_type <= type)
return 1;
break;
case SEARCH_EQUAL:
if (msg->m_type == type)
return 1;
break;
case SEARCH_NOTEQUAL:
if (msg->m_type != type)
return 1;
break;
}
return 0;
}
static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg,
struct wake_q_head *wake_q)
{
struct msg_receiver *msr, *t;
list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
!security_msg_queue_msgrcv(&msq->q_perm, msg, msr->r_tsk,
msr->r_msgtype, msr->r_mode)) {
list_del(&msr->r_list);
if (msr->r_maxsize < msg->m_ts) {
wake_q_add(wake_q, msr->r_tsk);
WRITE_ONCE(msr->r_msg, ERR_PTR(-E2BIG));
} else {
ipc_update_pid(&msq->q_lrpid, task_pid(msr->r_tsk));
msq->q_rtime = get_seconds();
wake_q_add(wake_q, msr->r_tsk);
WRITE_ONCE(msr->r_msg, msg);
return 1;
}
}
}
return 0;
}
static long do_msgsnd(int msqid, long mtype, void __user *mtext,
size_t msgsz, int msgflg)
{
struct msg_queue *msq;
struct msg_msg *msg;
int err;
struct ipc_namespace *ns;
DEFINE_WAKE_Q(wake_q);
ns = current->nsproxy->ipc_ns;
if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
return -EINVAL;
if (mtype < 1)
return -EINVAL;
msg = load_msg(mtext, msgsz);
if (IS_ERR(msg))
return PTR_ERR(msg);
msg->m_type = mtype;
msg->m_ts = msgsz;
rcu_read_lock();
msq = msq_obtain_object_check(ns, msqid);
if (IS_ERR(msq)) {
err = PTR_ERR(msq);
goto out_unlock1;
}
ipc_lock_object(&msq->q_perm);
for (;;) {
struct msg_sender s;
err = -EACCES;
if (ipcperms(ns, &msq->q_perm, S_IWUGO))
goto out_unlock0;
/* raced with RMID? */
if (!ipc_valid_object(&msq->q_perm)) {
err = -EIDRM;
goto out_unlock0;
}
err = security_msg_queue_msgsnd(&msq->q_perm, msg, msgflg);
if (err)
goto out_unlock0;
if (msg_fits_inqueue(msq, msgsz))
break;
/* queue full, wait: */
if (msgflg & IPC_NOWAIT) {
err = -EAGAIN;
goto out_unlock0;
}
/* enqueue the sender and prepare to block */
ss_add(msq, &s, msgsz);
if (!ipc_rcu_getref(&msq->q_perm)) {
err = -EIDRM;
goto out_unlock0;
}
ipc_unlock_object(&msq->q_perm);
rcu_read_unlock();
schedule();
rcu_read_lock();
ipc_lock_object(&msq->q_perm);
ipc_rcu_putref(&msq->q_perm, msg_rcu_free);
/* raced with RMID? */
if (!ipc_valid_object(&msq->q_perm)) {
err = -EIDRM;
goto out_unlock0;
}
ss_del(&s);
if (signal_pending(current)) {
err = -ERESTARTNOHAND;
goto out_unlock0;
}
}
ipc_update_pid(&msq->q_lspid, task_tgid(current));
msq->q_stime = get_seconds();
if (!pipelined_send(msq, msg, &wake_q)) {
/* no one is waiting for this message, enqueue it */
list_add_tail(&msg->m_list, &msq->q_messages);
msq->q_cbytes += msgsz;
msq->q_qnum++;
atomic_add(msgsz, &ns->msg_bytes);
atomic_inc(&ns->msg_hdrs);
}
err = 0;
msg = NULL;
out_unlock0:
ipc_unlock_object(&msq->q_perm);
wake_up_q(&wake_q);
out_unlock1:
rcu_read_unlock();
if (msg != NULL)
free_msg(msg);
return err;
}
long ksys_msgsnd(int msqid, struct msgbuf __user *msgp, size_t msgsz,
int msgflg)
{
long mtype;
if (get_user(mtype, &msgp->mtype))
return -EFAULT;
return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
}
SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
int, msgflg)
{
return ksys_msgsnd(msqid, msgp, msgsz, msgflg);
}
#ifdef CONFIG_COMPAT
struct compat_msgbuf {
compat_long_t mtype;
char mtext[1];
};
long compat_ksys_msgsnd(int msqid, compat_uptr_t msgp,
compat_ssize_t msgsz, int msgflg)
{
struct compat_msgbuf __user *up = compat_ptr(msgp);
compat_long_t mtype;
if (get_user(mtype, &up->mtype))
return -EFAULT;
return do_msgsnd(msqid, mtype, up->mtext, (ssize_t)msgsz, msgflg);
}
COMPAT_SYSCALL_DEFINE4(msgsnd, int, msqid, compat_uptr_t, msgp,
compat_ssize_t, msgsz, int, msgflg)
{
return compat_ksys_msgsnd(msqid, msgp, msgsz, msgflg);
}
#endif
static inline int convert_mode(long *msgtyp, int msgflg)
{
if (msgflg & MSG_COPY)
return SEARCH_NUMBER;
/*
* find message of correct type.
* msgtyp = 0 => get first.
* msgtyp > 0 => get first message of matching type.
* msgtyp < 0 => get message with least type must be < abs(msgtype).
*/
if (*msgtyp == 0)
return SEARCH_ANY;
if (*msgtyp < 0) {
if (*msgtyp == LONG_MIN) /* -LONG_MIN is undefined */
*msgtyp = LONG_MAX;
else
*msgtyp = -*msgtyp;
return SEARCH_LESSEQUAL;
}
if (msgflg & MSG_EXCEPT)
return SEARCH_NOTEQUAL;
return SEARCH_EQUAL;
}
static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
{
struct msgbuf __user *msgp = dest;
size_t msgsz;
if (put_user(msg->m_type, &msgp->mtype))
return -EFAULT;
msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
if (store_msg(msgp->mtext, msg, msgsz))
return -EFAULT;
return msgsz;
}
#ifdef CONFIG_CHECKPOINT_RESTORE
/*
* This function creates new kernel message structure, large enough to store
* bufsz message bytes.
*/
static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
{
struct msg_msg *copy;
/*
* Create dummy message to copy real message to.
*/
copy = load_msg(buf, bufsz);
if (!IS_ERR(copy))
copy->m_ts = bufsz;
return copy;
}
static inline void free_copy(struct msg_msg *copy)
{
if (copy)
free_msg(copy);
}
#else
static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
{
return ERR_PTR(-ENOSYS);
}
static inline void free_copy(struct msg_msg *copy)
{
}
#endif
static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
{
struct msg_msg *msg, *found = NULL;
long count = 0;
list_for_each_entry(msg, &msq->q_messages, m_list) {
if (testmsg(msg, *msgtyp, mode) &&
!security_msg_queue_msgrcv(&msq->q_perm, msg, current,
*msgtyp, mode)) {
if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
*msgtyp = msg->m_type - 1;
found = msg;
} else if (mode == SEARCH_NUMBER) {
if (*msgtyp == count)
return msg;
} else
return msg;
count++;
}
}
return found ?: ERR_PTR(-EAGAIN);
}
static long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
long (*msg_handler)(void __user *, struct msg_msg *, size_t))
{
int mode;
struct msg_queue *msq;
struct ipc_namespace *ns;
struct msg_msg *msg, *copy = NULL;
DEFINE_WAKE_Q(wake_q);
ns = current->nsproxy->ipc_ns;
if (msqid < 0 || (long) bufsz < 0)
return -EINVAL;
if (msgflg & MSG_COPY) {
if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
return -EINVAL;
copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
if (IS_ERR(copy))
return PTR_ERR(copy);
}
mode = convert_mode(&msgtyp, msgflg);
rcu_read_lock();
msq = msq_obtain_object_check(ns, msqid);
if (IS_ERR(msq)) {
rcu_read_unlock();
free_copy(copy);
return PTR_ERR(msq);
}
for (;;) {
struct msg_receiver msr_d;
msg = ERR_PTR(-EACCES);
if (ipcperms(ns, &msq->q_perm, S_IRUGO))
goto out_unlock1;
ipc_lock_object(&msq->q_perm);
/* raced with RMID? */
if (!ipc_valid_object(&msq->q_perm)) {
msg = ERR_PTR(-EIDRM);
goto out_unlock0;
}
msg = find_msg(msq, &msgtyp, mode);
if (!IS_ERR(msg)) {
/*
* Found a suitable message.
* Unlink it from the queue.
*/
if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
msg = ERR_PTR(-E2BIG);
goto out_unlock0;
}
/*
* If we are copying, then do not unlink message and do
* not update queue parameters.
*/
if (msgflg & MSG_COPY) {
msg = copy_msg(msg, copy);
goto out_unlock0;
}
list_del(&msg->m_list);
msq->q_qnum--;
msq->q_rtime = get_seconds();
ipc_update_pid(&msq->q_lrpid, task_tgid(current));
msq->q_cbytes -= msg->m_ts;
atomic_sub(msg->m_ts, &ns->msg_bytes);
atomic_dec(&ns->msg_hdrs);
ss_wakeup(msq, &wake_q, false);
goto out_unlock0;
}
/* No message waiting. Wait for a message */
if (msgflg & IPC_NOWAIT) {
msg = ERR_PTR(-ENOMSG);
goto out_unlock0;
}
list_add_tail(&msr_d.r_list, &msq->q_receivers);
msr_d.r_tsk = current;
msr_d.r_msgtype = msgtyp;
msr_d.r_mode = mode;
if (msgflg & MSG_NOERROR)
msr_d.r_maxsize = INT_MAX;
else
msr_d.r_maxsize = bufsz;
msr_d.r_msg = ERR_PTR(-EAGAIN);
__set_current_state(TASK_INTERRUPTIBLE);
ipc_unlock_object(&msq->q_perm);
rcu_read_unlock();
schedule();
/*
* Lockless receive, part 1:
* We don't hold a reference to the queue and getting a
* reference would defeat the idea of a lockless operation,
* thus the code relies on rcu to guarantee the existence of
* msq:
* Prior to destruction, expunge_all(-EIRDM) changes r_msg.
* Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
*/
rcu_read_lock();
/*
* Lockless receive, part 2:
* The work in pipelined_send() and expunge_all():
* - Set pointer to message
* - Queue the receiver task for later wakeup
* - Wake up the process after the lock is dropped.
*
* Should the process wake up before this wakeup (due to a
* signal) it will either see the message and continue ...
*/
msg = READ_ONCE(msr_d.r_msg);
if (msg != ERR_PTR(-EAGAIN))
goto out_unlock1;
/*
* ... or see -EAGAIN, acquire the lock to check the message
* again.
*/
ipc_lock_object(&msq->q_perm);
msg = msr_d.r_msg;
if (msg != ERR_PTR(-EAGAIN))
goto out_unlock0;
list_del(&msr_d.r_list);
if (signal_pending(current)) {
msg = ERR_PTR(-ERESTARTNOHAND);
goto out_unlock0;
}
ipc_unlock_object(&msq->q_perm);
}
out_unlock0:
ipc_unlock_object(&msq->q_perm);
wake_up_q(&wake_q);
out_unlock1:
rcu_read_unlock();
if (IS_ERR(msg)) {
free_copy(copy);
return PTR_ERR(msg);
}
bufsz = msg_handler(buf, msg, bufsz);
free_msg(msg);
return bufsz;
}
long ksys_msgrcv(int msqid, struct msgbuf __user *msgp, size_t msgsz,
long msgtyp, int msgflg)
{
return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
}
SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
long, msgtyp, int, msgflg)
{
return ksys_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg);
}
#ifdef CONFIG_COMPAT
static long compat_do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
{
struct compat_msgbuf __user *msgp = dest;
size_t msgsz;
if (put_user(msg->m_type, &msgp->mtype))
return -EFAULT;
msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
if (store_msg(msgp->mtext, msg, msgsz))
return -EFAULT;
return msgsz;
}
long compat_ksys_msgrcv(int msqid, compat_uptr_t msgp, compat_ssize_t msgsz,
compat_long_t msgtyp, int msgflg)
{
return do_msgrcv(msqid, compat_ptr(msgp), (ssize_t)msgsz, (long)msgtyp,
msgflg, compat_do_msg_fill);
}
COMPAT_SYSCALL_DEFINE5(msgrcv, int, msqid, compat_uptr_t, msgp,
compat_ssize_t, msgsz, compat_long_t, msgtyp,
int, msgflg)
{
return compat_ksys_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg);
}
#endif
int msg_init_ns(struct ipc_namespace *ns)
{
ns->msg_ctlmax = MSGMAX;
ns->msg_ctlmnb = MSGMNB;
ns->msg_ctlmni = MSGMNI;
atomic_set(&ns->msg_bytes, 0);
atomic_set(&ns->msg_hdrs, 0);
return ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
}
#ifdef CONFIG_IPC_NS
void msg_exit_ns(struct ipc_namespace *ns)
{
free_ipcs(ns, &msg_ids(ns), freeque);
idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
rhashtable_destroy(&ns->ids[IPC_MSG_IDS].key_ht);
}
#endif
#ifdef CONFIG_PROC_FS
static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
{
struct pid_namespace *pid_ns = ipc_seq_pid_ns(s);
struct user_namespace *user_ns = seq_user_ns(s);
struct kern_ipc_perm *ipcp = it;
struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
seq_printf(s,
"%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10llu %10llu %10llu\n",
msq->q_perm.key,
msq->q_perm.id,
msq->q_perm.mode,
msq->q_cbytes,
msq->q_qnum,
pid_nr_ns(msq->q_lspid, pid_ns),
pid_nr_ns(msq->q_lrpid, pid_ns),
from_kuid_munged(user_ns, msq->q_perm.uid),
from_kgid_munged(user_ns, msq->q_perm.gid),
from_kuid_munged(user_ns, msq->q_perm.cuid),
from_kgid_munged(user_ns, msq->q_perm.cgid),
msq->q_stime,
msq->q_rtime,
msq->q_ctime);
return 0;
}
#endif
int __init msg_init(void)
{
const int err = msg_init_ns(&init_ipc_ns);
ipc_init_proc_interface("sysvipc/msg",
" key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n",
IPC_MSG_IDS, sysvipc_msg_proc_show);
return err;
}