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

[Edward Adam Davis]

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..278cc4db922f 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1486,7 +1486,14 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)
 	int err;
 
 	lock_sock(sk);
-
+	sock_hold(sk);
+	l2cap_chan_hold(chan);
+	l2cap_chan_lock(chan);
+	if (sock_flag(sk, SOCK_DEAD)) {
+		err = -ENXIO;
+		goto done;
+	}
+		
 	if (chan->mode == L2CAP_MODE_ERTM && !list_empty(&pi->rx_busy)) {
 		err = -ENOMEM;
 		goto done;
@@ -1534,7 +1541,11 @@ 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);
+	sock_put(sk);
+	if (err != -ENXIO)
+		release_sock(sk);
 
 	return err;
 }