Patch "bridge: fix igmp / mld query parsing" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

bridge: fix igmp / mld query parsing

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
bridge-fix-igmp-mld-query-parsing.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: =?UTF-8?q?Linus=20L=C3=BCssing?= <[email protected]>
Date: Wed, 4 May 2016 17:25:02 +0200
Subject: bridge: fix igmp / mld query parsing
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From: =?UTF-8?q?Linus=20L=C3=BCssing?= <[email protected]>

[ Upstream commit 856ce5d083e14571d051301fe3c65b32b8cbe321 ]

With the newly introduced helper functions the skb pulling is hidden in the checksumming function - and undone before returning to the caller.

The IGMP and MLD query parsing functions in the bridge still assumed that the skb is pointing to the beginning of the IGMP/MLD message while it is now kept at the beginning of the IPv4/6 header.

If there is a querier somewhere else, then this either causes the multicast snooping to stay disabled even though it could be enabled. Or, if we have the querier enabled too, then this can create unnecessary IGMP / MLD query messages on the link.

Fixing this by taking the offset between IP and IGMP/MLD header into account, too.

---
 net/bridge/br_multicast.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

@@ -1270,6 +1270,7 @@ static int br_ip4_multicast_query(struct
 	struct br_ip saddr;
 	unsigned long max_delay;
 	unsigned long now = jiffies;
+	unsigned int offset = skb_transport_offset(skb);
 	__be32 group;
 	int err = 0;
 

@@ -1280,14 +1281,14 @@ static int br_ip4_multicast_query(struct
 
 	group = ih->group;
 
-	if (skb->len == sizeof(*ih)) {
+	if (skb->len == offset + sizeof(*ih)) {
 		max_delay = ih->code * (HZ / IGMP_TIMER_SCALE);
 
 		if (!max_delay) {
 			max_delay = 10 * HZ;
 			group = 0;
 		}
-	} else if (skb->len >= sizeof(*ih3)) {
+	} else if (skb->len >= offset + sizeof(*ih3)) {
 		ih3 = igmpv3_query_hdr(skb);
 		if (ih3->nsrcs)
 			goto out;

@@ -1348,6 +1349,7 @@ static int br_ip6_multicast_query(struct
 	struct br_ip saddr;
 	unsigned long max_delay;
 	unsigned long now = jiffies;
+	unsigned int offset = skb_transport_offset(skb);
 	const struct in6_addr *group = NULL;
 	bool is_general_query;
 	int err = 0;

@@ -1357,8 +1359,8 @@ static int br_ip6_multicast_query(struct
 	    (port && port->state == BR_STATE_DISABLED))
 		goto out;
 
-	if (skb->len == sizeof(*mld)) {
-		if (!pskb_may_pull(skb, sizeof(*mld))) {
+	if (skb->len == offset + sizeof(*mld)) {
+		if (!pskb_may_pull(skb, offset + sizeof(*mld))) {
 			err = -EINVAL;
 			goto out;
 		}

@@ -1367,7 +1369,7 @@ static int br_ip6_multicast_query(struct
 		if (max_delay)
 			group = &mld->mld_mca;
 	} else {
-		if (!pskb_may_pull(skb, sizeof(*mld2q))) {
+		if (!pskb_may_pull(skb, offset + sizeof(*mld2q))) {
 			err = -EINVAL;
 			goto out;
 		}

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/bridge-fix-igmp-mld-query-parsing.patch