Messages in this thread | | | Date | Mon, 25 Apr 2022 19:47:20 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v2 2/5] sched,ptrace: Fix ptrace_check_attach() vs PREEMPT_RT |
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On 04/21, Peter Zijlstra wrote: > > @@ -2225,7 +2238,7 @@ static int ptrace_stop(int exit_code, in > * schedule() will not sleep if there is a pending signal that > * can awaken the task. > */ > - current->jobctl |= JOBCTL_TRACED; > + current->jobctl |= JOBCTL_TRACED | JOBCTL_TRACED_QUIESCE; > set_special_state(TASK_TRACED);
OK, this looks wrong. I actually mean the previous patch which sets JOBCTL_TRACED.
The problem is that the tracee can be already killed, so that fatal_signal_pending(current) is true. In this case we can't rely on signal_wake_up_state() which should clear JOBCTL_TRACED, or the callers of ptrace_signal_wake_up/etc which clear this flag by hand.
In this case schedule() won't block and ptrace_stop() will leak JOBCTL_TRACED. Unless I missed something.
We could check fatal_signal_pending() and damn! this is what I think ptrace_stop() should have done from the very beginning. But for now I'd suggest to simply clear this flag before return, along with DELAY_WAKEKILL and LISTENING.
> current->jobctl &= ~JOBCTL_LISTENING; > + current->jobctl &= ~JOBCTL_DELAY_WAKEKILL;
current->jobctl &= ~(~JOBCTL_TRACED | JOBCTL_DELAY_WAKEKILL | JOBCTL_LISTENING);
Oleg.
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