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

From: Stefano Brivio <redacted>
Date: Tue, 13 Aug 2019 00:46:01 +0200

quoted

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 <redacted>

Applied and queued up for -stable.

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