tipc: improve size validations for received domain records

The function tipc_mon_rcv() allows a node to receive and process
domain_record structs from peer nodes to track their views of the
network topology.

This patch verifies that the number of members in a received domain
record does not exceed the limit defined by MAX_MON_DOMAIN, something
that may otherwise lead to a stack overflow.

tipc_mon_rcv() is called from the function tipc_link_proto_rcv(), where
we are reading a 32 bit message data length field into a uint16.  To
avert any risk of bit overflow, we add an extra sanity check for this in
that function.  We cannot see that happen with the current code, but
future designers being unaware of this risk, may introduce it by
allowing delivery of very large (> 64k) sk buffers from the bearer
layer.  This potential problem was identified by Eric Dumazet.

This fixes CVE-2022-0435
Reported-by: Samuel Page <samuel.page@appgate.com>
Reported-by: Eric Dumazet <edumazet@google.com>
Fixes: 35c55c98 ("tipc: add neighbor monitoring framework")
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Reviewed-by: Samuel Page <samuel.page@appgate.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

net/tipc/link.c

@@ -2200,7 +2200,7 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 	struct tipc_msg *hdr = buf_msg(skb);
 	struct tipc_gap_ack_blks *ga = NULL;
 	bool reply = msg_probe(hdr), retransmitted = false;
-	u16 dlen = msg_data_sz(hdr), glen = 0;
+	u32 dlen = msg_data_sz(hdr), glen = 0;
 	u16 peers_snd_nxt =  msg_next_sent(hdr);
 	u16 peers_tol = msg_link_tolerance(hdr);
 	u16 peers_prio = msg_linkprio(hdr);
@@ -2214,6 +2214,10 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 	void *data;
 
 	trace_tipc_proto_rcv(skb, false, l->name);
+
+	if (dlen > U16_MAX)
+		goto exit;
+
 	if (tipc_link_is_blocked(l) || !xmitq)
 		goto exit;
 
@@ -2309,7 +2313,8 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 
 		/* Receive Gap ACK blocks from peer if any */
 		glen = tipc_get_gap_ack_blks(&ga, l, hdr, true);
-
+		if(glen > dlen)
+			break;
 		tipc_mon_rcv(l->net, data + glen, dlen - glen, l->addr,
 			     &l->mon_state, l->bearer_id);
 

net/tipc/monitor.c

@@ -496,6 +496,8 @@ void tipc_mon_rcv(struct net *net, void *data, u16 dlen, u32 addr,
 	state->probing = false;
 
 	/* Sanity check received domain record */
+	if (new_member_cnt > MAX_MON_DOMAIN)
+		return;
 	if (dlen < dom_rec_len(arrv_dom, 0))
 		return;
 	if (dlen != dom_rec_len(arrv_dom, new_member_cnt))