net/x25: fix null_x25_address handling

BugLink: https://bugs.launchpad.net/bugs/1858489

[ Upstream commit 06137619 ]

o x25_find_listener(): the compare for the null_x25_address was wrong.
   We have to check the x25_addr of the listener socket instead of the
   x25_addr of the incomming call.

 o x25_bind(): it was not possible to bind a socket to null_x25_address
Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/x25/af_x25.c

@@ -288,7 +288,7 @@ static struct sock *x25_find_listener(struct x25_address *addr,
 	sk_for_each(s, &x25_list)
 		if ((!strcmp(addr->x25_addr,
 			x25_sk(s)->source_addr.x25_addr) ||
-				!strcmp(addr->x25_addr,
+				!strcmp(x25_sk(s)->source_addr.x25_addr,
 					null_x25_address.x25_addr)) &&
 					s->sk_state == TCP_LISTEN) {
 			/*
@@ -684,6 +684,9 @@ static int x25_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 		goto out;
 	}
 
+	/* check for the null_x25_address */
+	if (strcmp(addr->sx25_addr.x25_addr, null_x25_address.x25_addr)) {
+
 		len = strlen(addr->sx25_addr.x25_addr);
 		for (i = 0; i < len; i++) {
 			if (!isdigit(addr->sx25_addr.x25_addr[i])) {
@@ -691,6 +694,7 @@ static int x25_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 				goto out;
 			}
 		}
+	}
 
 	lock_sock(sk);
 	if (sock_flag(sk, SOCK_ZAPPED)) {