netdev - Re: [PATCH net] ipv6: Fix return value of ipv6_mc_may

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Message-Id: <20190814.125858.37782529545578263.davem@davemloft.net>
Date:   Wed, 14 Aug 2019 12:58:58 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     sbrivio@...hat.com
Cc:     gnault@...hat.com, haliu@...hat.com, edumazet@...gle.com,
        linus.luessing@...3.blue, netdev@...r.kernel.org
Subject: Re: [PATCH net] ipv6: Fix return value of ipv6_mc_may_pull() for
 malformed packets

From: Stefano Brivio <sbrivio@...hat.com>
Date: Tue, 13 Aug 2019 00:46:01 +0200

> Commit ba5ea614622d ("bridge: simplify ip_mc_check_igmp() and
> ipv6_mc_check_mld() calls") replaces direct calls to pskb_may_pull()
> in br_ipv6_multicast_mld2_report() with calls to ipv6_mc_may_pull(),
> that returns -EINVAL on buffers too short to be valid IPv6 packets,
> while maintaining the previous handling of the return code.
> 
> This leads to the direct opposite of the intended effect: if the
> packet is malformed, -EINVAL evaluates as true, and we'll happily
> proceed with the processing.
> 
> Return 0 if the packet is too short, in the same way as this was
> fixed for IPv4 by commit 083b78a9ed64 ("ip: fix ip_mc_may_pull()
> return value").
> 
> I don't have a reproducer for this, unlike the one referred to by
> the IPv4 commit, but this is clearly broken.
> 
> Fixes: ba5ea614622d ("bridge: simplify ip_mc_check_igmp() and ipv6_mc_check_mld() calls")
> Signed-off-by: Stefano Brivio <sbrivio@...hat.com>

Applied and queued up for -stable.