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Date:   Tue, 10 Mar 2020 13:47:51 -0700
From:   Kees Cook <keescook@chromium.org>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Bernd Edlinger <bernd.edlinger@hotmail.de>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Jann Horn <jannh@google.com>, Jonathan Corbet <corbet@lwn.net>,
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        Andrew Morton <akpm@linux-foundation.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Oleg Nesterov <oleg@redhat.com>,
        Frederic Weisbecker <frederic@kernel.org>,
        Andrei Vagin <avagin@gmail.com>,
        Ingo Molnar <mingo@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Yuyang Du <duyuyang@gmail.com>,
        David Hildenbrand <david@redhat.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
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Subject: Re: [PATCH v2 4/5] exec: Move exec_mmap right after de_thread in
 flush_old_exec
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On Sun, Mar 08, 2020 at 04:38:00PM -0500, Eric W. Biederman wrote:
> Futher this consolidates all of the possible indefinite waits for
> userspace together at the top of flush_old_exec.  The possible wait
> for a ptracer on PTRACE_EVENT_EXIT, the possible wait for a page fault
> to be resolved in clear_child_tid, and the possible wait for a page
> fault in exit_robust_list.

I forgot to mention, just as a point of clarity, there are lots of
other page faults possible, but they're _before_ flush_old_exec()
(i.e. all the copy_strings() calls). Is it worth clarifying this to
"before or at the top of flush_old_exec()" or do you mean something
else? (And as always: perhaps expand flush_old_exec()'s comment to
describe the newly intended state.)

-- 
Kees Cook