netdev - Re: [PATCH net] ax25: fix possible use-after-free

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Date:   Wed, 23 Jan 2019 11:18:16 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        ralf@...ux-mips.org, syzkaller@...glegroups.com
Subject: Re: [PATCH net] ax25: fix possible use-after-free

From: Eric Dumazet <edumazet@...gle.com>
Date: Tue, 22 Jan 2019 10:40:59 -0800

> syzbot found that ax25 routes where not properly protected
> against concurrent use [1].
> 
> In this particular report the bug happened while
> copying ax25->digipeat.
> 
> Fix this problem by making sure we call ax25_get_route()
> while ax25_route_lock is held, so that no modification
> could happen while using the route.
> 
> The current two ax25_get_route() callers do not sleep,
> so this change should be fine.
> 
> Once we do that, ax25_get_route() no longer needs to
> grab a reference on the found route.
> 
> [1]
 ...
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Ralf Baechle <ralf@...ux-mips.org>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied.