Re: [PATCH v2 2/5] sched,ptrace: Fix ptrace_check_attach() vs PREEMPT_RT
From: Peter Zijlstra
Date: Thu Apr 28 2022 - 16:29:37 EST
On Tue, Apr 26, 2022 at 07:24:03PM -0500, Eric W. Biederman wrote:
> But doing:
>
> /* Don't stop if the task is dying */
> if (unlikely(__fatal_signal_pending(current)))
> return exit_code;
>
> Should work.
Something like so then...
---
Subject: signal,ptrace: Don't stop dying tasks
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Thu Apr 28 22:17:56 CEST 2022
Oleg pointed out that the tracee can already be killed such that
fatal_signal_pending() is true. In that case signal_wake_up_state()
cannot be relied upon to be responsible for the wakeup -- something
we're going to want to rely on.
As such, explicitly handle this case.
Suggested-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
kernel/signal.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2226,6 +2226,10 @@ static int ptrace_stop(int exit_code, in
spin_lock_irq(¤t->sighand->siglock);
}
+ /* Don't stop if the task is dying. */
+ if (unlikely(__fatal_signal_pending(current)))
+ return exit_code;
+
/*
* schedule() will not sleep if there is a pending signal that
* can awaken the task.