llc: Check netns in llc_dgram_match().

We will remove this restriction in llc_rcv() soon, which means that the
protocol handler must be aware of netns.

	if (!net_eq(dev_net(dev), &init_net))
		goto drop;

llc_rcv() fetches llc_type_handlers[llc_pdu_type(skb) - 1] and calls it
if not NULL.

If the PDU type is LLC_DEST_SAP, llc_sap_handler() is called to pass skb
to corresponding sockets.  Then, we must look up a proper socket in the
same netns with skb->dev.

If the destination is a multicast address, llc_sap_handler() calls
llc_sap_mcast().  It calculates a hash based on DSAP and skb->dev->ifindex,
iterates on a socket list, and calls llc_mcast_match() to check if the
socket is the correct destination.  Then, llc_mcast_match() checks if
skb->dev matches with llc_sk(sk)->dev.  So, we need not check netns here.

OTOH, if the destination is a unicast address, llc_sap_handler() calls
llc_lookup_dgram() to look up a socket, but it does not check the netns.

Therefore, we need to add netns check in llc_lookup_dgram().
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/llc/llc_sap.c

@@ -294,25 +294,29 @@ static void llc_sap_rcv(struct llc_sap *sap, struct sk_buff *skb,
 
 static inline bool llc_dgram_match(const struct llc_sap *sap,
 				   const struct llc_addr *laddr,
-				   const struct sock *sk)
+				   const struct sock *sk,
+				   const struct net *net)
 {
      struct llc_sock *llc = llc_sk(sk);
 
      return sk->sk_type == SOCK_DGRAM &&
-	  llc->laddr.lsap == laddr->lsap &&
-	  ether_addr_equal(llc->laddr.mac, laddr->mac);
+	     net_eq(sock_net(sk), net) &&
+	     llc->laddr.lsap == laddr->lsap &&
+	     ether_addr_equal(llc->laddr.mac, laddr->mac);
 }
 
 /**
  *	llc_lookup_dgram - Finds dgram socket for the local sap/mac
  *	@sap: SAP
  *	@laddr: address of local LLC (MAC + SAP)
+ *	@net: netns to look up a socket in
  *
  *	Search socket list of the SAP and finds connection using the local
  *	mac, and local sap. Returns pointer for socket found, %NULL otherwise.
  */
 static struct sock *llc_lookup_dgram(struct llc_sap *sap,
-				     const struct llc_addr *laddr)
+				     const struct llc_addr *laddr,
+				     const struct net *net)
 {
 	struct sock *rc;
 	struct hlist_nulls_node *node;
@@ -322,12 +326,12 @@ static struct sock *llc_lookup_dgram(struct llc_sap *sap,
 	rcu_read_lock_bh();
 again:
 	sk_nulls_for_each_rcu(rc, node, laddr_hb) {
-		if (llc_dgram_match(sap, laddr, rc)) {
+		if (llc_dgram_match(sap, laddr, rc, net)) {
 			/* Extra checks required by SLAB_TYPESAFE_BY_RCU */
 			if (unlikely(!refcount_inc_not_zero(&rc->sk_refcnt)))
 				goto again;
 			if (unlikely(llc_sk(rc)->sap != sap ||
-				     !llc_dgram_match(sap, laddr, rc))) {
+				     !llc_dgram_match(sap, laddr, rc, net))) {
 				sock_put(rc);
 				continue;
 			}
@@ -429,7 +433,7 @@ void llc_sap_handler(struct llc_sap *sap, struct sk_buff *skb)
 		llc_sap_mcast(sap, &laddr, skb);
 		kfree_skb(skb);
 	} else {
-		struct sock *sk = llc_lookup_dgram(sap, &laddr);
+		struct sock *sk = llc_lookup_dgram(sap, &laddr, dev_net(skb->dev));
 		if (sk) {
 			llc_sap_rcv(sap, skb, sk);
 			sock_put(sk);