netdev - Re: [PATCH net 2/2] ipv6: protect mtu calculation of wrap-around and infinite loop by rounding issues

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Message-Id: <20151029.070311.2268753886894108048.davem@davemloft.net>
Date:	Thu, 29 Oct 2015 07:03:11 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	hannes@...essinduktion.org
Cc:	netdev@...r.kernel.org, torvalds@...ux-foundation.org,
	dvyukov@...gle.com
Subject: Re: [PATCH net 2/2] ipv6: protect mtu calculation of wrap-around
 and infinite loop by rounding issues

From: Hannes Frederic Sowa <hannes@...essinduktion.org>
Date: Wed, 28 Oct 2015 13:21:04 +0100

> Raw sockets with hdrincl enabled can insert ipv6 extension headers
> right into the data stream. In case we need to fragment those packets,
> we reparse the options header to find the place where we can insert
> the fragment header. If the extension headers exceed the link's MTU we
> actually cannot make progress in such a case.
> 
> Instead of ending up in broken arithmetic or rounding towards 0 and
> entering an endless loop in ip6_fragment, just prevent those cases by
> aborting early and signal -EMSGSIZE to user space.
> 
> This is the second version of the patch which doesn't use the
> overflow_usub function, which got reverted for now.
> 
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Applied.
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