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Date: Mon, 20 Feb 2017 16:36:30 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Mika =?iso-8859-1?Q?Penttil=E4?= <mika.penttila@nextfour.com>,
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        Kees Cook <keescook@chromium.org>, Michal Hocko <mhocko@kernel.org>,
        Ulrich Obergfell <uobergfe@redhat.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2 1/2] exec: don't wait for zombie threads with
        cred_guard_mutex held
Message-ID: <20170220153629.GA13975@redhat.com>
References: <20170213141452.GA30203@redhat.com> <20170213141516.GA30233@redhat.com> <20170213180454.GA2858@redhat.com> <87zihmpdkf.fsf@xmission.com> <20170220152202.GA13726@redhat.com>
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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.