linux-kernel - Re: [PATCH v4] net: don't call strlen on non-terminated string in dev_set

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Date:   Tue, 6 Jun 2017 23:15:11 +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>, stephen@...workplumber.org,
        LKML <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH v4] net: don't call strlen on non-terminated string in dev_set_alias()

On Tue, Jun 6, 2017 at 10:36 PM, David Miller <davem@...emloft.net> wrote:
> From: Alexander Potapenko <glider@...gle.com>
> Date: Tue,  6 Jun 2017 15:56:54 +0200
>
>> KMSAN reported a use of uninitialized memory in dev_set_alias(),
>> which was caused by calling strlcpy() (which in turn called strlen())
>> on the user-supplied non-terminated string.
>>
>> Signed-off-by: Alexander Potapenko <glider@...gle.com>
>
> We should not be allowing non-NULL terminated strings for the
> IFLA_IFALIAS attribute.  It's defined as type NLA_STRING in
> the ifla_policy[] array.
Sorry, I couldn't determine from RFC 2233 whether ifAlias is
zero-terminated or not, but looking at validate_nla() I see that
NLA_STRING is supposed to be such.
I'll check what's going on.

> Please figure out why we aren't enforcing the attribute policy
> properly, rather than adding a workaround.
Guess the string has been previously claimed to be non-terminated
here: https://patchwork.ozlabs.org/patch/996/
> Thanks.



-- 
Alexander Potapenko
Software Engineer

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