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inline | side by side (from parent 1:
a97c9bf)
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>
timr->sigq->info.si_code = SI_TIMER;
timr->sigq->info.si_tid = timr->it_id;
timr->sigq->info.si_value = timr->it_sigev_value;
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 (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);
}
EXPORT_SYMBOL_GPL(posix_timer_event);
unsigned long flags;
int ret = 0;
unsigned long flags;
int ret = 0;
- /*
- * We need the tasklist lock even for the specific
- * thread case (when we don't need to follow the group
- * lists) in order to avoid races with "p->sighand"
- * going away or changing from under us.
- */
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
- read_lock(&tasklist_lock);
+ read_lock(&tasklist_lock);
+
+ if (unlikely(p->flags & PF_EXITING)) {
+ ret = -1;
+ goto out_err;
+ }
+
spin_lock_irqsave(&p->sighand->siglock, flags);
spin_lock_irqsave(&p->sighand->siglock, flags);
if (unlikely(!list_empty(&q->list))) {
/*
* If an SI_TIMER entry is already queue just increment
if (unlikely(!list_empty(&q->list))) {
/*
* If an SI_TIMER entry is already queue just increment
BUG();
q->info.si_overrun++;
goto out;
BUG();
q->info.si_overrun++;
goto out;
/* Short-circuit ignored signals. */
if (sig_ignored(p, sig)) {
ret = 1;
/* Short-circuit ignored signals. */
if (sig_ignored(p, sig)) {
ret = 1;
out:
spin_unlock_irqrestore(&p->sighand->siglock, flags);
out:
spin_unlock_irqrestore(&p->sighand->siglock, flags);
read_unlock(&tasklist_lock);
read_unlock(&tasklist_lock);