linux-kernel - Re: [PATCH v2] exec: don't force_sigsegv processes with a pending fatal signal

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Date:   Mon, 11 Feb 2019 17:02:56 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Ivan Delalande <colona@...sta.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v2] exec: don't force_sigsegv processes with a pending
 fatal signal

On 02/08, Ivan Delalande wrote:
>
> A difference I've noticed with your tree (unrelated to my issue here but
> that you may want to look at) is when I run my reproducer under
> strace -f, I'm now getting quite a lot of "Exit of unknown pid 12345
> ignored" warnings from strace, which I've never seen with mainline.
> My reproducer simply fork-exec tail processes in a loop, and tries to
> sigkill them in the parent with a variable delay.

Hmm... may be because of PTRACE_EVENT_EXIT problem I mentioned in reply
to this change...

> 
> Thank you,
> 
> > diff --git a/kernel/signal.c b/kernel/signal.c
> > index 9ca8e5278c8e..5424cb0006bc 100644
> > --- a/kernel/signal.c
> > +++ b/kernel/signal.c
> > @@ -2393,6 +2393,11 @@ bool get_signal(struct ksignal *ksig)
> >                 goto relock;
> >         }
> >  
> > +       /* Has this task already been marked for death? */
> > +       ksig->info.si_signo = signr = SIGKILL;
> > +       if (signal_group_exit(signal))
> > +               goto fatal;
> > +
> >         for (;;) {
> >                 struct k_sigaction *ka;
> >  
> > @@ -2488,6 +2493,7 @@ bool get_signal(struct ksignal *ksig)
> >                         continue;
> >                 }
> >  
> > +       fatal:
> >                 spin_unlock_irq(&sighand->siglock);
> >  
> >    
> 
> -- 
> Ivan Delalande
> Arista Networks