linux-kernel - Re: [PATCH] tcp: no md5sig option size check bug

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Date:	Sat, 07 Aug 2010 20:24:16 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	dp@...hloadlab.com
Cc:	kuznet@....inr.ac.ru, jmorris@...ei.org, kaber@...sh.net,
	yoshfuji@...ux-ipv6.org, pekkas@...core.fi, gilad@...efidence.com,
	yony@...sleep.com, ori@...sleep.com, ilpo.jarvinen@...sinki.fi,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tcp: no md5sig option size check bug

From: Dmitry Popov <dp@...hloadlab.com>
Date: Sat, 7 Aug 2010 23:17:52 +0400

> From: Dmitry Popov <dp@...hloadlab.com>
> 
> tcp_parse_md5sig_option doesn't check md5sig option (TCPOPT_MD5SIG)
> length, but tcp_v[46]_inbound_md5_hash assume that it's at least 16
> bytes long.
> 
> Signed-off-by: Dmitry Popov <dp@...hloadlab.com>

I'll apply this, but the memcmp() we do against this pointer is always
safe because there's at least skb_shared_info()'s worth of valid
memory past skb->data guarenteed at all times which is much larger
than 16 bytes.

So at worst we'd access garbage, but never past a valid piece of
allocated memory.

Thanks.
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