Re: [syzbot] [bluetooth?] general protection fault in l2cap_sock_recv_cb

Edward Adam Davis
2024-06-11T06:35:58Z

please test null ptr defref in l2cap_sock_recv_cb

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git cc8ed4d0a848

diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 6db60946c627..a9edcf9152c3 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1413,6 +1413,9 @@ static int l2cap_sock_release(struct socket *sock)
l2cap_chan_hold(chan);
l2cap_chan_lock(chan);

+ printk("chan %p data: %p, sk: %p, %s\n", chan, chan->data, sk, __func__);
+ if (refcount_read(&sk->sk_refcnt))
+ chan->data = NULL;
sock_orphan(sk);
l2cap_sock_kill(sk);

@@ -1481,12 +1484,23 @@ static struct l2cap_chan *l2cap_sock_new_connection_cb(struct l2cap_chan *chan)

static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)
{
- struct sock *sk = chan->data;
- struct l2cap_pinfo *pi = l2cap_pi(sk);
+ struct sock *sk;
+ struct l2cap_pinfo *pi;
int err;

- lock_sock(sk);
+ l2cap_chan_hold(chan);
+ l2cap_chan_lock(chan);
+ sk = chan->data;

+ printk("chan %p data: %p, is :%d, %s\n", chan, chan->data, IS_ERR_OR_NULL(sk), __func__);
+ if (IS_ERR_OR_NULL(sk) || sock_flag(sk, SOCK_DEAD)) {
+ l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
+ return -ENXIO;
+ }
+
+ pi = l2cap_pi(sk);
+ lock_sock(sk);
if (chan->mode == L2CAP_MODE_ERTM && !list_empty(&pi->rx_busy)) {
err = -ENOMEM;
goto done;
@@ -1535,6 +1549,8 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)

done:
release_sock(sk);
+ l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);

return err;
}