Messages in this thread Patch in this message | | | Date | Thu, 23 Aug 2007 15:26:19 -0700 | From | Greg KH <> | Subject | [patch 06/28] signalfd: fix interaction with posix-timers |
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-stable review patch. If anyone has any objections, please let us know.
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From: Oleg Nesterov <oleg@tv-sign.ru>
dequeue_signal:
if (__SI_TIMER) { spin_unlock(&tsk->sighand->siglock); do_schedule_next_timer(info); spin_lock(&tsk->sighand->siglock); }
Unless tsk == curent, this is absolutely unsafe: nothing prevents tsk from exiting. If signalfd was passed to another process, do_schedule_next_timer() is just wrong.
Add yet another "tsk == current" check into dequeue_signal().
This patch fixes an oopsable bug, but breaks the scheduling of posix timers if the shared __SI_TIMER signal was fetched via signalfd attached to another sub-thread. Mostly fixed by the next patch.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Roland McGrath <roland@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- kernel/signal.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/signal.c +++ b/kernel/signal.c @@ -368,7 +368,7 @@ int dequeue_signal(struct task_struct *t /* We only dequeue private signals from ourselves, we don't let * signalfd steal them */ - if (tsk == current) + if (likely(tsk == current)) signr = __dequeue_signal(&tsk->pending, mask, info); if (!signr) { signr = __dequeue_signal(&tsk->signal->shared_pending, @@ -415,7 +415,7 @@ int dequeue_signal(struct task_struct *t if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT)) tsk->signal->flags |= SIGNAL_STOP_DEQUEUED; } - if ( signr && + if (signr && likely(tsk == current) && ((info->si_code & __SI_MASK) == __SI_TIMER) && info->si_sys_private){ /* -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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