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[PATCH] fix send_sigqueue() vs thread exit race

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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>
This commit is contained in:
Oleg Nesterov
2005-09-06 15:17:42 -07:00
committed by Linus Torvalds
parent a97c9bf33f
commit e752dd6cc6
2 changed files with 27 additions and 23 deletions
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28
kernel/posix-timers.c
View File

@ -427,21 +427,23 @@ int posix_timer_event(struct k_itimer *timr,int si_private)
timr->sigq->info.si_code = SI_TIMER;
timr->sigq->info.si_tid = timr->it_id;
timr->sigq->info.si_value = timr->it_sigev_value;
if (timr->it_sigev_notify & SIGEV_THREAD_ID) {
if (unlikely(timr->it_process->flags & PF_EXITING)) {
timr->it_sigev_notify = SIGEV_SIGNAL;
put_task_struct(timr->it_process);
timr->it_process = timr->it_process->group_leader;
goto group;
}
return send_sigqueue(timr->it_sigev_signo, timr->sigq,
timr->it_process);
}
else {
group:
return send_group_sigqueue(timr->it_sigev_signo, timr->sigq,
timr->it_process);
struct task_struct *leader;
int ret = send_sigqueue(timr->it_sigev_signo, timr->sigq,
timr->it_process);
if (likely(ret >= 0))
return ret;
timr->it_sigev_notify = SIGEV_SIGNAL;
leader = timr->it_process->group_leader;
put_task_struct(timr->it_process);
timr->it_process = leader;
}
return send_group_sigqueue(timr->it_sigev_signo, timr->sigq,
timr->it_process);
}
EXPORT_SYMBOL_GPL(posix_timer_event);