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

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Message-ID: <20190814182604.GD2431@otheros>
Date:   Wed, 14 Aug 2019 20:26:04 +0200
From:   Linus Lüssing <linus.luessing@...3.blue>
To:     David Miller <davem@...emloft.net>
Cc:     bridge@...ts.linux-foundation.org, sbrivio@...hat.com,
        gnault@...hat.com, haliu@...hat.com, edumazet@...gle.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net] ipv6: Fix return value of ipv6_mc_may_pull() for
 malformed packets

On Wed, Aug 14, 2019 at 12:58:58PM -0400, David Miller wrote:
> 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.

Urgh, sorry... and thanks for the fix(es), absolutely right...