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.
Signed-off-by: Hyunwoo Kim <v4bel@xxxxxxxxx>
---
net/bluetooth/af_bluetooth.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index 336a76165454..9def13ac816e 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -309,11 +309,16 @@ 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)
+ if (sk->sk_shutdown & RCV_SHUTDOWN) {
+ release_sock(sk);
return 0;
+ }
+ release_sock(sk);
return err;
}
@@ -343,6 +348,8 @@ 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;
--
2.25.1
