diff options
| author | Oleg Nesterov <oleg@tv-sign.ru> | 2005-09-06 15:17:42 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-09-07 16:57:33 -0700 |
| commit | e752dd6cc66a3e6a11396928998baf390cc00420 (patch) | |
| tree | b24b388d80acec6527e66b07f0d308d48319c476 /kernel/signal.c | |
| parent | a97c9bf33f4612e2aed6f000f6b1d268b6814f3c (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/signal.c')
| -rw-r--r-- | kernel/signal.c | 22 |
1 files changed, 12 insertions, 10 deletions
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 |