oss-security - Linux: ip: fix IP_CHECKSUM handling (CVE-2017-6347)

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Date: Tue, 28 Feb 2017 17:23:09 +0100
From: Salvatore Bonaccorso <carnil@...ian.org>
To: OSS Security Mailinglist <oss-security@...ts.openwall.com>
Subject: Linux: ip: fix IP_CHECKSUM handling (CVE-2017-6347)

Hi

CVE-2017-6347 was assigned by MITRE to the following (via
https://cveform.mitre.org/):

https://git.kernel.org/linus/ca4ef4574f1ee5252e2cd365f8f5d5bafd048f32

> ip: fix IP_CHECKSUM handling
> 
> The skbs processed by ip_cmsg_recv() are not guaranteed to
> be linear e.g. when sending UDP packets over loopback with
> MSGMORE.
> Using csum_partial() on [potentially] the whole skb len
> is dangerous; instead be on the safe side and use skb_checksum().
> 
> Thanks to syzkaller team to detect the issue and provide the
> reproducer.

The issue was introduced in 4.0 by commit ad6f939ab193. The fix as
well backported to 4.9.13.

Regards,
Salvatore

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