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

From: David Miller
Date: Sat Aug 07 2010 - 23:24:28 EST

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

> From: Dmitry Popov <dp@xxxxxxxxxxxxxxx>
> 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@xxxxxxxxxxxxxxx>

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.

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