linux-kernel - Re: [PATCH] net/dccp: fix use after free in tw_timer

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Message-ID: <6b21534b-060d-9eac-53f1-7fb3ec448358@virtuozzo.com>
Date:   Wed, 22 Feb 2017 11:59:03 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
CC:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Gerrit Renker <gerrit@....abdn.ac.uk>,
        "David S. Miller" <davem@...emloft.net>, <dccp@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        <syzkaller@...glegroups.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net/dccp: fix use after free in tw_timer_handler()

On 02/21/2017 04:43 PM, Arnaldo Carvalho de Melo wrote:
> Em Tue, Feb 21, 2017 at 02:27:40PM +0300, Andrey Ryabinin escreveu:
>> DCCP doesn't purge timewait sockets on network namespace shutdown.
>> So, after net namespace destroyed we could still have an active timer
>> which will trigger use after free in tw_timer_handler():
>>
>>
>> Add .exit_batch hook to dccp_v4_ops()/dccp_v6_ops() which will purge
>> timewait sockets on net namespace destruction and prevent above issue.
> 
> Please add this, to help stable kernels to pick this up
> 
> Fixes: b099ce2602d8 ("net: Batch inet_twsk_purge")
> Cc: Eric W. Biederman <ebiederm@...ssion.com> 
> 

Fixes tag should blame commit f2bf415cfed7 ("mib: add net to NET_ADD_STATS_BH").
It introduced use of net namespace in the timer callback.