Re: [syzbot] Re: [syzbot] [bluetooth?] BUG: corrupted list in hci_chan_del (2)

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Subject: Re: [syzbot] [bluetooth?] BUG: corrupted list in hci_chan_del (2)
Author: lizhi.xu@windriver.com

old logical will make get/put unbalance in l2cap_recv_acldata.
so remote get/put conn.
protect conn refcnt under hci dev lock.

#syz test

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index adb8c33ac595..503626f70be5 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -7497,8 +7497,6 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
 	if (!conn)
 		conn = l2cap_conn_add(hcon);
 
-	conn = l2cap_conn_hold_unless_zero(conn);
-
 	hci_dev_unlock(hcon->hdev);
 
 	if (!conn)
@@ -7592,8 +7590,6 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
 		break;
 	}
 
-	l2cap_conn_put(conn);
-
 drop:
 	kfree_skb(skb);
 }
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 46ea0bee2259..2a99394925a5 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1359,10 +1359,12 @@ static int l2cap_sock_shutdown(struct socket *sock, int how)
 
 	l2cap_chan_lock(chan);
 	conn = chan->conn;
-	if (conn)
+	l2cap_chan_unlock(chan);
+	if (conn) {
+		hci_dev_lock(conn->hcon->hdev);
 		/* prevent conn structure from being freed */
 		l2cap_conn_get(conn);
-	l2cap_chan_unlock(chan);
+	}
 
 	if (conn)
 		/* mutex lock must be taken before l2cap_chan_lock() */
@@ -1375,6 +1377,7 @@ static int l2cap_sock_shutdown(struct socket *sock, int how)
 	if (conn) {
 		mutex_unlock(&conn->chan_lock);
 		l2cap_conn_put(conn);
+		hci_dev_unlock(conn->hcon->hdev);
 	}
 
 	lock_sock(sk);