On 03/29, Peter Zijlstra wrote:
>
> On Thu, Mar 25, 2021 at 09:14:39AM +0100, Marco Elver wrote:
> > @@ -6395,6 +6395,13 @@ static void perf_sigtrap(struct perf_event *event)
> > {
> > struct kernel_siginfo info;
> >
> > + /*
> > + * This irq_work can race with an exiting task; bail out if sighand has
> > + * already been released in release_task().
> > + */
> > + if (!current->sighand)
> > + return;
This is racy. If "current" has already passed exit_notify(), current->parent
can do release_task() and destroy current->sighand right after the check.
> Urgh.. I'm not entirely sure that check is correct, but I always forget
> the rules with signal. It could be we ought to be testing PF_EXISTING
> instead.
Agreed, PF_EXISTING check makes more sense in any case, the exiting task
can't receive the signal anyway.
Oleg.
