Bluetooth: af_bluetooth: Fix Use-After-Free in bt_sock_recvmsg

jira VULN-470
cve CVE-2023-51779
commit-author Hyunwoo Kim <[email protected]>
commit 2e07e83

This can cause a race with bt_sock_ioctl() because
bt_sock_recvmsg() gets the skb from sk->sk_receive_queue
and then frees it without holding lock_sock.
A use-after-free for a skb occurs with the following flow.
```
bt_sock_recvmsg() -> skb_recv_datagram() -> skb_free_datagram()
bt_sock_ioctl() -> skb_peek()
```
Add lock_sock to bt_sock_recvmsg() to fix this issue.

	Cc: [email protected]
Fixes: 1da177e ("Linux-2.6.12-rc2")
	Signed-off-by: Hyunwoo Kim <[email protected]>
	Signed-off-by: Luiz Augusto von Dentz <[email protected]>
(cherry picked from commit 2e07e83)
	Signed-off-by: Brett Mastbergen <[email protected]>

Author: bmastbergen

net/bluetooth/af_bluetooth.c

@@ -264,11 +264,14 @@ int bt_sock_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	if (flags & MSG_OOB)
 		return -EOPNOTSUPP;
 
+	lock_sock(sk);
+
 	skb = skb_recv_datagram(sk, flags, &err);
 	if (!skb) {
 		if (sk->sk_shutdown & RCV_SHUTDOWN)
-			return 0;
+			err = 0;
 
+		release_sock(sk);
 		return err;
 	}
 
@@ -294,6 +297,8 @@ int bt_sock_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 
 	skb_free_datagram(sk, skb);
 
+	release_sock(sk);
+
 	if (flags & MSG_TRUNC)
 		copied = skblen;