Messages in this thread | | | Date | Mon, 29 Mar 2021 16:27:06 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v3 06/11] perf: Add support for SIGTRAP on perf events |
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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.
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