Merge branch 'bridge-stale-ptrs'

Nikolay Aleksandrov says:

====================
net: bridge: fix possible stale skb pointers

In the bridge driver we have a couple of places which call pskb_may_pull
but we've cached skb pointers before that and use them after which can
lead to out-of-bounds/stale pointer use. I've had these in my "to fix"
list for some time and now we got a report (patch 01) so here they are.
Patches 02-04 are fixes based on code inspection. Also patch 01 was
tested by Martin Weinelt, Martin if you don't mind please add your
tested-by tag to it by replying with Tested-by: name <email>.
I've also briefly tested the set by trying to exercise those code paths.
====================

Signed-off-by: David S. Miller <[e-mail]>

net/bridge/br_input.c

···
 	struct net_bridge_fdb_entry *dst = NULL;
 	struct net_bridge_mdb_entry *mdst;
 	bool local_rcv, mcast_hit = false;
-	const unsigned char *dest;
 	struct net_bridge *br;
 	u16 vid = 0;
 
···
 		br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
 
 	local_rcv = !!(br->dev->flags & IFF_PROMISC);
-	dest = eth_hdr(skb)->h_dest;
-	if (is_multicast_ether_addr(dest)) {
+	if (is_multicast_ether_addr(eth_hdr(skb)->h_dest)) {
 		/* by definition the broadcast is also a multicast address */
-		if (is_broadcast_ether_addr(dest)) {
+		if (is_broadcast_ether_addr(eth_hdr(skb)->h_dest)) {
 			pkt_type = BR_PKT_BROADCAST;
 			local_rcv = true;
 		} else {
···
 		}
 		break;
 	case BR_PKT_UNICAST:
-		dst = br_fdb_find_rcu(br, dest, vid);
+		dst = br_fdb_find_rcu(br, eth_hdr(skb)->h_dest, vid);
 	default:
 		break;
 	}

net/bridge/br_multicast.c

···
 	int type;
 	int err = 0;
 	__be32 group;
+	u16 nsrcs;
 
 	ih = igmpv3_report_hdr(skb);
 	num = ntohs(ih->ngrec);
···
 		grec = (void *)(skb->data + len - sizeof(*grec));
 		group = grec->grec_mca;
 		type = grec->grec_type;
+		nsrcs = ntohs(grec->grec_nsrcs);
 
-		len += ntohs(grec->grec_nsrcs) * 4;
+		len += nsrcs * 4;
 		if (!ip_mc_may_pull(skb, len))
 			return -EINVAL;
 
···
 		src = eth_hdr(skb)->h_source;
 		if ((type == IGMPV3_CHANGE_TO_INCLUDE ||
 		     type == IGMPV3_MODE_IS_INCLUDE) &&
-		    ntohs(grec->grec_nsrcs) == 0) {
+		    nsrcs == 0) {
 			br_ip4_multicast_leave_group(br, port, group, vid, src);
 		} else {
 			err = br_ip4_multicast_add_group(br, port, group, vid,
···
 	len = skb_transport_offset(skb) + sizeof(*icmp6h);
 
 	for (i = 0; i < num; i++) {
-		__be16 *nsrcs, _nsrcs;
+		__be16 *_nsrcs, __nsrcs;
+		u16 nsrcs;
 
 		nsrcs_offset = len + offsetof(struct mld2_grec, grec_nsrcs);
 
···
 		    nsrcs_offset + sizeof(_nsrcs))
 			return -EINVAL;
 
-		nsrcs = skb_header_pointer(skb, nsrcs_offset,
-					   sizeof(_nsrcs), &_nsrcs);
-		if (!nsrcs)
+		_nsrcs = skb_header_pointer(skb, nsrcs_offset,
+					    sizeof(__nsrcs), &__nsrcs);
+		if (!_nsrcs)
 			return -EINVAL;
 
-		grec_len = struct_size(grec, grec_src, ntohs(*nsrcs));
+		nsrcs = ntohs(*_nsrcs);
+		grec_len = struct_size(grec, grec_src, nsrcs);
 
 		if (!ipv6_mc_may_pull(skb, len + grec_len))
 			return -EINVAL;
···
 		src = eth_hdr(skb)->h_source;
 		if ((grec->grec_type == MLD2_CHANGE_TO_INCLUDE ||
 		     grec->grec_type == MLD2_MODE_IS_INCLUDE) &&
-		    ntohs(*nsrcs) == 0) {
+		    nsrcs == 0) {
 			br_ip6_multicast_leave_group(br, port, &grec->grec_mca,
 						     vid, src);
 		} else {
···
 				  u16 vid)
 {
 	unsigned int transport_len = ipv6_transport_len(skb);
-	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 	struct mld_msg *mld;
 	struct net_bridge_mdb_entry *mp;
 	struct mld2_query *mld2q;
···
 
 	if (is_general_query) {
 		saddr.proto = htons(ETH_P_IPV6);
-		saddr.u.ip6 = ip6h->saddr;
+		saddr.u.ip6 = ipv6_hdr(skb)->saddr;
 
 		br_multicast_query_received(br, port, &br->ip6_other_query,
 					    &saddr, max_delay);

net/bridge/br_stp_bpdu.c

···
 void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
 		struct net_device *dev)
 {
-	const unsigned char *dest = eth_hdr(skb)->h_dest;
 	struct net_bridge_port *p;
 	struct net_bridge *br;
 	const unsigned char *buf;
···
 	if (p->state == BR_STATE_DISABLED)
 		goto out;
 
-	if (!ether_addr_equal(dest, br->group_addr))
+	if (!ether_addr_equal(eth_hdr(skb)->h_dest, br->group_addr))
 		goto out;
 
 	if (p->flags & BR_BPDU_GUARD) {