netdev - Re: [PATCH] ipv6: properly prevent temp_prefered

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Message-Id: <20161020.142929.1228552177893783734.davem@davemloft.net>
Date:   Thu, 20 Oct 2016 14:29:29 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     jbohac@...e.cz
Cc:     julia.lawall@...6.fr, kuznet@....inr.ac.ru, jmorris@...ei.org,
        yoshfuji@...ux-ipv6.org, kaber@...sh.net, netdev@...r.kernel.org,
        kbuild-all@...org
Subject: Re: [PATCH] ipv6: properly prevent temp_prefered_lft sysctl race

From: Jiri Bohac <jbohac@...e.cz>
Date: Thu, 20 Oct 2016 12:29:26 +0200

> The check for an underflow of tmp_prefered_lft is always false
> because tmp_prefered_lft is unsigned. The intention of the check
> was to guard against racing with an update of the
> temp_prefered_lft sysctl, potentially resulting in an underflow.
> 
> As suggested by David Miller, the best way to prevent the race is
> by reading the sysctl variable using READ_ONCE.
> 
> Signed-off-by: Jiri Bohac <jbohac@...e.cz>
> Reported-by: Julia Lawall <julia.lawall@...6.fr>
> Fixes: 76506a986dc3 ("IPv6: fix DESYNC_FACTOR")

Applied, thanks Jiri.