Paul E. McKenney wrote:
>
> --- linux-2.6.13-rc6/kernel/signal.c 2005-08-08 19:59:24.000000000 -0700
> +++ linux-2.6.13-rc6-tasklistRCU/kernel/signal.c 2005-08-10 08:20:25.000000000 -0700
> @@ -1151,9 +1151,13 @@ int group_send_sig_info(int sig, struct
>
> ret = check_kill_permission(sig, info, p);
> if (!ret && sig && p->sighand) {
> + if (!get_task_struct_rcu(p)) {
> + return -ESRCH;
> + }
> spin_lock_irqsave(&p->sighand->siglock, flags);
^^^^^^^
Is it correct?
The caller (kill_proc_info) does not take tasklist_lock anymore.
If p does exec() at this time it can change/free its ->sighand.
fs/exec.c:de_thread()
773 write_lock_irq(&tasklist_lock);
774 spin_lock(&oldsighand->siglock);
775 spin_lock(&newsighand->siglock);
776
777 current->sighand = newsighand;
778 recalc_sigpending();
779
780 spin_unlock(&newsighand->siglock);
781 spin_unlock(&oldsighand->siglock);
782 write_unlock_irq(&tasklist_lock);
783
784 if (atomic_dec_and_test(&oldsighand->count))
785 kmem_cache_free(sighand_cachep, oldsighand);
Oleg.
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