Hi Kim,
On Mon, Dec 4, 2023 at 2:02 AM Hyunwoo Kim <v4bel@xxxxxxxxx> wrote:
>
> 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);
We could just reset the with err = 0 then we don't need to duplicate
the release_sock line.
> 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
>
--
Luiz Augusto von Dentz
