Merge branch 'tipc-fixes'

Xin Long says:

====================
tipc: fix the mtu update in link mtu negotiation

This patchset fixes a crash caused by a too small MTU carried in the
activate msg. Note that as such malicious packet does not exist in
the normal env, the fix won't break any application

The 1st patch introduces a function to calculate the minimum MTU for
the bearer, and the 2nd patch fixes the crash with this helper. While
at it, the 3rd patch fixes the udp bearer mtu update by netlink with
this helper.
====================

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

net/tipc/bearer.c

···
 	return mtu;
 }
 
+int tipc_bearer_min_mtu(struct net *net, u32 bearer_id)
+{
+	int mtu = TIPC_MIN_BEARER_MTU;
+	struct tipc_bearer *b;
+
+	rcu_read_lock();
+	b = bearer_get(net, bearer_id);
+	if (b)
+		mtu += b->encap_hlen;
+	rcu_read_unlock();
+	return mtu;
+}
+
 /* tipc_bearer_xmit_skb - sends buffer to destination over bearer
  */
 void tipc_bearer_xmit_skb(struct net *net, u32 bearer_id,
···
 				return -EINVAL;
 			}
 #ifdef CONFIG_TIPC_MEDIA_UDP
-			if (tipc_udp_mtu_bad(nla_get_u32
-					     (props[TIPC_NLA_PROP_MTU]))) {
+			if (nla_get_u32(props[TIPC_NLA_PROP_MTU]) <
+			    b->encap_hlen + TIPC_MIN_BEARER_MTU) {
 				NL_SET_ERR_MSG(info->extack,
 					       "MTU value is out-of-range");
 				return -EINVAL;

net/tipc/bearer.h

···
  * @identity: array index of this bearer within TIPC bearer array
  * @disc: ptr to link setup request
  * @net_plane: network plane ('A' through 'H') currently associated with bearer
+ * @encap_hlen: encap headers length
  * @up: bearer up flag (bit 0)
  * @refcnt: tipc_bearer reference counter
  *
···
 	u32 identity;
 	struct tipc_discoverer *disc;
 	char net_plane;
+	u16 encap_hlen;
 	unsigned long up;
 	refcount_t refcnt;
 };
···
 void tipc_bearer_cleanup(void);
 void tipc_bearer_stop(struct net *net);
 int tipc_bearer_mtu(struct net *net, u32 bearer_id);
+int tipc_bearer_min_mtu(struct net *net, u32 bearer_id);
 bool tipc_bearer_bcast_support(struct net *net, u32 bearer_id);
 void tipc_bearer_xmit_skb(struct net *net, u32 bearer_id,
 			  struct sk_buff *skb,

net/tipc/link.c

···
 	struct tipc_msg *hdr = buf_msg(skb);
 	struct tipc_gap_ack_blks *ga = NULL;
 	bool reply = msg_probe(hdr), retransmitted = false;
-	u32 dlen = msg_data_sz(hdr), glen = 0;
+	u32 dlen = msg_data_sz(hdr), glen = 0, msg_max;
 	u16 peers_snd_nxt =  msg_next_sent(hdr);
 	u16 peers_tol = msg_link_tolerance(hdr);
 	u16 peers_prio = msg_linkprio(hdr);
···
 	switch (mtyp) {
 	case RESET_MSG:
 	case ACTIVATE_MSG:
+		msg_max = msg_max_pkt(hdr);
+		if (msg_max < tipc_bearer_min_mtu(l->net, l->bearer_id))
+			break;
 		/* Complete own link name with peer's interface name */
 		if_name =  strrchr(l->name, ':') + 1;
 		if (sizeof(l->name) - (if_name - l->name) <= TIPC_MAX_IF_NAME)
···
 		l->peer_session = msg_session(hdr);
 		l->in_session = true;
 		l->peer_bearer_id = msg_bearer_id(hdr);
-		if (l->mtu > msg_max_pkt(hdr))
-			l->mtu = msg_max_pkt(hdr);
+		if (l->mtu > msg_max)
+			l->mtu = msg_max;
 		break;
 
 	case STATE_MSG:

net/tipc/udp_media.c

···
 			udp_conf.local_ip.s_addr = local.ipv4.s_addr;
 		udp_conf.use_udp_checksums = false;
 		ub->ifindex = dev->ifindex;
-		if (tipc_mtu_bad(dev, sizeof(struct iphdr) +
-				      sizeof(struct udphdr))) {
+		b->encap_hlen = sizeof(struct iphdr) + sizeof(struct udphdr);
+		if (tipc_mtu_bad(dev, b->encap_hlen)) {
 			err = -EINVAL;
 			goto err;
 		}
···
 		else
 			udp_conf.local_ip6 = local.ipv6;
 		ub->ifindex = dev->ifindex;
+		b->encap_hlen = sizeof(struct ipv6hdr) + sizeof(struct udphdr);
 		b->mtu = 1280;
 #endif
 	} else {