linux-kernel - Re: [PATCH] ipv6: ensure message length for raw socket is at least sizeof(ipv6hdr)

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Message-Id: <20170425.135543.1706004185593424024.davem@davemloft.net>
Date:   Tue, 25 Apr 2017 13:55:43 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     glider@...gle.com
Cc:     dvyukov@...gle.com, kcc@...gle.com, edumazet@...gle.com,
        kuznet@....inr.ac.ru, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH] ipv6: ensure message length for raw socket is at least
 sizeof(ipv6hdr)

From: Alexander Potapenko <glider@...gle.com>
Date: Tue, 25 Apr 2017 15:18:27 +0200

> rawv6_send_hdrinc() expects that the buffer copied from the userspace
> contains the IPv6 header, so if too few bytes are copied parts of the
> header may remain uninitialized.
> 
> This bug has been detected with KMSAN.
> 
> Signed-off-by: Alexander Potapenko <glider@...gle.com>

Hmmm, ipv4 seems to lack this check as well.

I think we need to be careful here and fully understand why KMSAN doesn't
seem to be triggering in the ipv4 case but for ipv6 it is before I apply
this.

Thanks.