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authorOleg Nesterov <oleg@tv-sign.ru>2008-05-23 13:04:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-05-24 09:56:10 -0700
commitda7978b0348d497688541e2d2f5739aa2a2c334f (patch)
treef4f55bf4293ff203f598e7a57959da1c5a7ad295 /kernel/exit.c
parentdfc7064500061677720fa26352963c772d3ebe6b (diff)
downloadlinux-da7978b0348d497688541e2d2f5739aa2a2c334f.tar.gz
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>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r--kernel/exit.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 1510f78a0ff..8f6185e69b6 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);