linux-kernel - Re: [PATCH] mm: get_cmdline use arg_lock instead of mmap

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Message-ID: <20190417144142.GF8962@blackbody.suse.cz>
Date:   Wed, 17 Apr 2019 16:41:42 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        Arun KS <arunks@...eaurora.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Mateusz Guzik <mguzik@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: get_cmdline use arg_lock instead of mmap_sem

On Wed, Apr 17, 2019 at 03:41:52PM +0200, Michal Hocko <mhocko@...nel.org> wrote:
> Don't we need to use the lock in prctl_set_mm as well then?

Correct. The patch alone just moves the race from
get_cmdline/prctl_set_mm_map to get_cmdline/prctl_set_mm.

arg_lock could be used in prctl_set_mm but the better idea (IMO) is
complete removal of that code in favor of prctl_set_mm_map [1].

Michal

[1] https://lore.kernel.org/lkml/20180405182651.GM15783@uranus.lan/