sctp: read sk->sk_bound_dev_if once in sctp_rcv()

sctp_rcv() reads sk->sk_bound_dev_if twice while the socket is not locked. Another cpu could change this field under us. Fixes: 0fd9a65 ("[SCTP] Support SO_BINDTODEVICE socket option on incoming packets.") Signed-off-by: Eric Dumazet <[email protected]> Cc: Neil Horman <[email protected]> Cc: Vlad Yasevich <[email protected]> Cc: Marcelo Ricardo Leitner <[email protected]> Acked-by: Marcelo Ricardo Leitner <[email protected]> Signed-off-by: David S. Miller <[email protected]>
ambv · May 16, 2022 · a20ea29 · a20ea29
1 parent 4c971d2
commit a20ea29
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/net/sctp/input.c b/net/sctp/input.c
@@ -92,6 +92,7 @@ int sctp_rcv(struct sk_buff *skb)
 	struct sctp_chunk *chunk;
 	union sctp_addr src;
 	union sctp_addr dest;
+	int bound_dev_if;
 	int family;
 	struct sctp_af *af;
 	struct net *net = dev_net(skb->dev);
@@ -169,7 +170,8 @@ int sctp_rcv(struct sk_buff *skb)
 	 * If a frame arrives on an interface and the receiving socket is
 	 * bound to another interface, via SO_BINDTODEVICE, treat it as OOTB
 	 */
-	if (sk->sk_bound_dev_if && (sk->sk_bound_dev_if != af->skb_iif(skb))) {
+	bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
+	if (bound_dev_if && (bound_dev_if != af->skb_iif(skb))) {
 		if (transport) {
 			sctp_transport_put(transport);
 			asoc = NULL;