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authorOleg Nesterov <oleg@tv-sign.ru>2005-09-06 15:17:42 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-07 16:57:33 -0700
commite752dd6cc66a3e6a11396928998baf390cc00420 (patch)
treeb24b388d80acec6527e66b07f0d308d48319c476 /kernel
parenta97c9bf33f4612e2aed6f000f6b1d268b6814f3c (diff)
[PATCH] fix send_sigqueue() vs thread exit race
posix_timer_event() first checks that the thread (SIGEV_THREAD_ID case) does not have PF_EXITING flag, then it calls send_sigqueue() which locks task list. But if the thread exits in between the kernel will oops (->sighand == NULL after __exit_sighand). This patch moves the PF_EXITING check into the send_sigqueue(), it must be done atomically under tasklist_lock. When send_sigqueue() detects exiting thread it returns -1. In that case posix_timer_event will send the signal to thread group. Also, this patch fixes task_struct use-after-free in posix_timer_event. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/posix-timers.c28
-rw-r--r--kernel/signal.c22
2 files changed, 27 insertions, 23 deletions
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 38798a2ff994..b7b532acd9fc 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -427,21 +427,23 @@ int posix_timer_event(struct k_itimer *timr,int si_private)
timr->sigq->info.si_code = SI_TIMER;
timr->sigq->info.si_tid = timr->it_id;
timr->sigq->info.si_value = timr->it_sigev_value;
+
if (timr->it_sigev_notify & SIGEV_THREAD_ID) {
- if (unlikely(timr->it_process->flags & PF_EXITING)) {
- timr->it_sigev_notify = SIGEV_SIGNAL;
- put_task_struct(timr->it_process);
- timr->it_process = timr->it_process->group_leader;
- goto group;
- }
- return send_sigqueue(timr->it_sigev_signo, timr->sigq,
- timr->it_process);
- }
- else {
- group:
- return send_group_sigqueue(timr->it_sigev_signo, timr->sigq,
- timr->it_process);
+ struct task_struct *leader;
+ int ret = send_sigqueue(timr->it_sigev_signo, timr->sigq,
+ timr->it_process);
+
+ if (likely(ret >= 0))
+ return ret;
+
+ timr->it_sigev_notify = SIGEV_SIGNAL;
+ leader = timr->it_process->group_leader;
+ put_task_struct(timr->it_process);
+ timr->it_process = leader;
}
+
+ return send_group_sigqueue(timr->it_sigev_signo, timr->sigq,
+ timr->it_process);
}
EXPORT_SYMBOL_GPL(posix_timer_event);
diff --git a/kernel/signal.c b/kernel/signal.c
index 56e33df2b67f..4980a073237f 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1366,16 +1366,16 @@ send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
unsigned long flags;
int ret = 0;
- /*
- * We need the tasklist lock even for the specific
- * thread case (when we don't need to follow the group
- * lists) in order to avoid races with "p->sighand"
- * going away or changing from under us.
- */
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
- read_lock(&tasklist_lock);
+ read_lock(&tasklist_lock);
+
+ if (unlikely(p->flags & PF_EXITING)) {
+ ret = -1;
+ goto out_err;
+ }
+
spin_lock_irqsave(&p->sighand->siglock, flags);
-
+
if (unlikely(!list_empty(&q->list))) {
/*
* If an SI_TIMER entry is already queue just increment
@@ -1385,7 +1385,7 @@ send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
BUG();
q->info.si_overrun++;
goto out;
- }
+ }
/* Short-circuit ignored signals. */
if (sig_ignored(p, sig)) {
ret = 1;
@@ -1400,8 +1400,10 @@ send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
out:
spin_unlock_irqrestore(&p->sighand->siglock, flags);
+out_err:
read_unlock(&tasklist_lock);
- return(ret);
+
+ return ret;
}
int

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