linux-kernel - Re: [PATCH V2 1/2] exec: don't wait for zombie threads with cred_guard

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Message-ID: <20170220153629.GA13975@redhat.com>
Date:   Mon, 20 Feb 2017 16:36:30 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mika Penttilä <mika.penttila@...tfour.com>,
        Aleksa Sarai <asarai@...e.com>,
        Andy Lutomirski <luto@...capital.net>,
        Attila Fazekas <afazekas@...hat.com>,
        Jann Horn <jann@...jh.net>, Kees Cook <keescook@...omium.org>,
        Michal Hocko <mhocko@...nel.org>,
        Ulrich Obergfell <uobergfe@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/2] exec: don't wait for zombie threads with
        cred_guard_mutex held

On 02/20, Oleg Nesterov wrote:
>
> Again, this needs some work. For example check_unsafe_exec() assumes
> it can't race with another thread, see 9e00cdb091b008cb3c78192651180
> "exec:check_unsafe_exec: kill the dead -EAGAIN and clear_in_exec logic".
> But this looks solvable.

Forgot to mention... plus check_unsafe_exec() checks ptrace, this is
another reason why we can't simply shift mutex_lock(cred_guard_mutex)
later.

Oleg.