Bluetooth: Fix potential NULL dereference in RFCOMM bind callback

commit 951b6a07 upstream.

addr can be NULL and it should not be dereferenced before NULL checking.
Signed-off-by: Jaganath Kanakkassery <jaganath.k@samsung.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
[bwh: Backported to 3.2:
 - There's no 'chan' variable
 - Keep using batostr() to log addresses
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/bluetooth/rfcomm/sock.c

@@ -349,15 +349,19 @@ static int rfcomm_sock_create(struct net *net, struct socket *sock,
 
 static int rfcomm_sock_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 {
-	struct sockaddr_rc *sa = (struct sockaddr_rc *) addr;
+	struct sockaddr_rc sa;
 	struct sock *sk = sock->sk;
-	int err = 0;
-
-	BT_DBG("sk %p %s", sk, batostr(&sa->rc_bdaddr));
+	int len, err = 0;
 
 	if (!addr || addr->sa_family != AF_BLUETOOTH)
 		return -EINVAL;
 
+	memset(&sa, 0, sizeof(sa));
+	len = min_t(unsigned int, sizeof(sa), addr_len);
+	memcpy(&sa, addr, len);
+
+	BT_DBG("sk %p %s", sk, batostr(&sa.rc_bdaddr));
+
 	lock_sock(sk);
 
 	if (sk->sk_state != BT_OPEN) {
@@ -372,12 +376,13 @@ static int rfcomm_sock_bind(struct socket *sock, struct sockaddr *addr, int addr
 
 	write_lock_bh(&rfcomm_sk_list.lock);
 
-	if (sa->rc_channel && __rfcomm_get_sock_by_addr(sa->rc_channel, &sa->rc_bdaddr)) {
+	if (sa.rc_channel &&
+	    __rfcomm_get_sock_by_addr(sa.rc_channel, &sa.rc_bdaddr)) {
 		err = -EADDRINUSE;
 	} else {
 		/* Save source address */
-		bacpy(&bt_sk(sk)->src, &sa->rc_bdaddr);
-		rfcomm_pi(sk)->channel = sa->rc_channel;
+		bacpy(&bt_sk(sk)->src, &sa.rc_bdaddr);
+		rfcomm_pi(sk)->channel = sa.rc_channel;
 		sk->sk_state = BT_BOUND;
 	}