diff options
| author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-05-23 22:04:41 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-05-24 18:56:10 +0200 |
| commit | da7978b0348d497688541e2d2f5739aa2a2c334f (patch) | |
| tree | f4f55bf4293ff203f598e7a57959da1c5a7ad295 | |
| parent | md: restart recovery cleanly after device failure. (diff) | |
| download | linux-da7978b0348d497688541e2d2f5739aa2a2c334f.tar.xz linux-da7978b0348d497688541e2d2f5739aa2a2c334f.zip | |
signals: fix sigqueue_free() vs __exit_signal() race
__exit_signal() does flush_sigqueue(tsk->pending) outside of ->siglock.
This can race with another thread doing sigqueue_free(), we can free the
same SIGQUEUE_PREALLOC sigqueue twice or corrupt the pending->list.
Note that even sys_exit_group() can trigger this race, not only
sys_timer_delete().
Move the callsite of flush_sigqueue(tsk->pending) under ->siglock.
This patch doesn't touch flush_sigqueue(->shared_pending) below, it is
called when there are no other threads which can play with signals, and
sigqueue_free() can't be used outside of our thread group.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | kernel/exit.c | 7 | ||||
| -rw-r--r-- | kernel/signal.c | 3 |
2 files changed, 8 insertions, 2 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 1510f78a0ffa..8f6185e69b69 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -126,6 +126,12 @@ static void __exit_signal(struct task_struct *tsk) __unhash_process(tsk); + /* + * Do this under ->siglock, we can race with another thread + * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals. + */ + flush_sigqueue(&tsk->pending); + tsk->signal = NULL; tsk->sighand = NULL; spin_unlock(&sighand->siglock); @@ -133,7 +139,6 @@ static void __exit_signal(struct task_struct *tsk) __cleanup_sighand(sighand); clear_tsk_thread_flag(tsk,TIF_SIGPENDING); - flush_sigqueue(&tsk->pending); if (sig) { flush_sigqueue(&sig->shared_pending); taskstats_tgid_free(sig); diff --git a/kernel/signal.c b/kernel/signal.c index 72bb4f51f963..12ffea7c201d 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1242,7 +1242,8 @@ void sigqueue_free(struct sigqueue *q) /* * If the signal is still pending remove it from the * pending queue. We must hold ->siglock while testing - * q->list to serialize with collect_signal(). + * q->list to serialize with collect_signal() or with + * __exit_signal()->flush_sigqueue(). */ spin_lock_irqsave(lock, flags); if (!list_empty(&q->list)) |