linux-kernel - Re: [syzbot] Re: [syzbot] [bluetooth?] BUG: corrupted list in hci_chan

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Message-ID: <67a5aa25.050a0220.2b1e6.0012.GAE@google.com>
Date: Thu, 06 Feb 2025 22:37:25 -0800
From: syzbot <syzbot+10bd8fe6741eedd2be2e@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org
Subject: 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@...driver.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..697e3b56f119 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1359,9 +1359,11 @@ static int l2cap_sock_shutdown(struct socket *sock, int how)
 
 	l2cap_chan_lock(chan);
 	conn = chan->conn;
-	if (conn)
+	if (conn) {
+		hci_dev_lock(conn->hcon->hdev);
 		/* prevent conn structure from being freed */
 		l2cap_conn_get(conn);
+	}
 	l2cap_chan_unlock(chan);
 
 	if (conn)
@@ -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);