-stable review patch. If anyone has any objections, please let us know.
------------------
From: Oleg Nesterov <[email protected]>
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 <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Davide Libenzi <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Roland McGrath <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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){
/*
--
-
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