From 2e07e8348ea454615e268222ae3fc240421be768 Mon Sep 17 00:00:00 2001
From: Hyunwoo Kim <v4bel@theori.io>
Date: Sat, 9 Dec 2023 05:55:18 -0500
Subject: [PATCH] Bluetooth: af_bluetooth: Fix Use-After-Free in bt_sock_recvmsg
Git-commit: 2e07e8348ea454615e268222ae3fc240421be768
Patch-mainline: v6.7-rc7
References: CVE-2023-51779 bsc#1218559

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: stable@vger.kernel.org
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 net/bluetooth/af_bluetooth.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -263,11 +263,14 @@ int bt_sock_recvmsg(struct socket *sock,
 	if (flags & MSG_OOB)
 		return -EOPNOTSUPP;
 
+	lock_sock(sk);
+
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb) {
 		if (sk->sk_shutdown & RCV_SHUTDOWN)
-			return 0;
+			err = 0;
 
+		release_sock(sk);
 		return err;
 	}
 
@@ -293,6 +296,8 @@ int bt_sock_recvmsg(struct socket *sock,
 
 	skb_free_datagram(sk, skb);
 
+	release_sock(sk);
+
 	if (flags & MSG_TRUNC)
 		copied = skblen;