netdev - Re: [PATCH net] ip6_gre: fix ip6gre

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Date:   Sun, 05 Feb 2017 17:23:39 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     netdev@...r.kernel.org, andreyknvl@...gle.com
Subject: Re: [PATCH net] ip6_gre: fix ip6gre_err() invalid reads

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sat, 04 Feb 2017 23:18:55 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Andrey Konovalov reported out of bound accesses in ip6gre_err()
> 
> If GRE flags contains GRE_KEY, the following expression
> *(((__be32 *)p) + (grehlen / 4) - 1)
> 
> accesses data ~40 bytes after the expected point, since
> grehlen includes the size of IPv6 headers.
> 
> Let's use a "struct gre_base_hdr *greh" pointer to make this
> code more readable. 
> 
> p[1] becomes greh->protocol.
> grhlen is the GRE header length.
> 
> Fixes: c12b395a4664 ("gre: Support GRE over IPv6")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Andrey Konovalov <andreyknvl@...gle.com>

So the bug is that we include offset twice in the calculation.

Applied and queued up for -stable, thanks.