linux-kernel - Re: [PATCH] net: rtnetlink: bail out from rtnl_fdb

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Message-ID: <CAG_fn=WNnkmZ8CXqM6w7p_kmhh8Tys1HjgkfASYjvEZ2iie0hg@mail.gmail.com>
Date:   Wed, 31 May 2017 10:56:47 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     David Miller <davem@...emloft.net>
Cc:     Dmitriy Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: rtnetlink: bail out from rtnl_fdb_dump() on parse error

Hi David,

I've noticed that the upstream patch:
https://github.com/torvalds/linux/commit/0ff50e83b5122e836ca492fefb11656b225ac29c
contains the KMSAN report and the repro, despite I've put them under
the triple dash (IIRC Eric told me I shouldn't bloat the patch
descriptions with that information). Did I mess it up somehow?

Alex

On Wed, May 24, 2017 at 9:32 PM, David Miller <davem@...emloft.net> wrote:
> From: Alexander Potapenko <glider@...gle.com>
> Date: Tue, 23 May 2017 13:20:28 +0200
>
>> rtnl_fdb_dump() failed to check the result of nlmsg_parse(), which led
>> to contents of |ifm| being uninitialized because nlh->nlmsglen was too
>> small to accommodate |ifm|. The uninitialized data may affect some
>> branches and result in unwanted effects, although kernel data doesn't
>> seem to leak to the userspace directly.
>>
>> The bug has been detected with KMSAN and syzkaller.
>>
>> Signed-off-by: Alexander Potapenko <glider@...gle.com>
>
> Applied, thanks.



-- 
Alexander Potapenko
Software Engineer

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