linux-kernel - [PATCH 5.4 005/215] bridge: mcast: Fix MLD2 Report IPv6 payload length check

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Date:   Mon, 20 Jul 2020 17:34:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        Linus LÃ¼ssing <linus.luessing@...3.blue>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.4 005/215] bridge: mcast: Fix MLD2 Report IPv6 payload length check

From: "Linus Lüssing" <linus.luessing@...3.blue>

[ Upstream commit 5fc6266af7b427243da24f3443a50cd4584aac06 ]

Commit e57f61858b7c ("net: bridge: mcast: fix stale nsrcs pointer in
igmp3/mld2 report handling") introduced a bug in the IPv6 header payload
length check which would potentially lead to rejecting a valid MLD2 Report:

The check needs to take into account the 2 bytes for the "Number of
Sources" field in the "Multicast Address Record" before reading it.
And not the size of a pointer to this field.

Fixes: e57f61858b7c ("net: bridge: mcast: fix stale nsrcs pointer in igmp3/mld2 report handling")
Acked-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Signed-off-by: Linus LÃ¼ssing <linus.luessing@...3.blue>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/bridge/br_multicast.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1007,7 +1007,7 @@ static int br_ip6_multicast_mld2_report(
 		nsrcs_offset = len + offsetof(struct mld2_grec, grec_nsrcs);
 
 		if (skb_transport_offset(skb) + ipv6_transport_len(skb) <
-		    nsrcs_offset + sizeof(_nsrcs))
+		    nsrcs_offset + sizeof(__nsrcs))
 			return -EINVAL;
 
 		_nsrcs = skb_header_pointer(skb, nsrcs_offset,