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From:   Keno Fischer <keno@juliacomputing.com>
Date:   Fri, 8 Jul 2022 19:22:01 -0400
Message-ID: <CABV8kRxQNPUzLaJ1tFF8H-E_iqCkz0+Ac5rPBurnmA3GcofMmQ@mail.gmail.com>
Subject: Re: [PATCH 0/3] ptrace: Stop supporting SIGKILL for PTRACE_EVENT_EXIT
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        mingo@kernel.org,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Jann Horn <jannh@google.com>,
        Kees Cook <keescook@chromium.org>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        "Robert O'Callahan" <roc@pernos.co>, Kyle Huey <khuey@pernos.co>,
        Oleg Nesterov <oleg@redhat.com>
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Hi Eric,

On Fri, Jul 8, 2022 at 6:25 PM Eric W. Biederman <ebiederm@xmission.com> wrote:
> > Recently I had a conversation where it was pointed out to me that
> > SIGKILL sent to a tracee stropped in PTRACE_EVENT_EXIT is quite
> > difficult for a tracer to handle.
> >
>
> RR folks any comments?
>
> Did I properly understand what Keno Fischer was asking for when we
> talked in person?

Yes, this is indeed what I had in mind. I have not yet had the opportunity
to try out your patch series (sorry), but from visual inspection, it does indeed
do what I wanted, which is to make sure that a tracee stays in
PTRACE_EVENT_EXIT for the tracer to inspect, even if there is another
SIGKILL incoming simultaneously (since otherwise it may be impossible
for the tracer to observe the PTRACE_EVENT_EXIT if two SIGKILLs
come in rapid succession). I will try to take this series for a proper spin
shortly.

Keno