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

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Message-ID: <67a5877d.050a0220.2b1e6.000e.GAE@google.com>
Date: Thu, 06 Feb 2025 20:09:33 -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.
move chan_del from l2cap_conn_free to conn_del, avoid up level l2cap_sock_release double call it.

#syz test

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index adb8c33ac595..bbaf2141578b 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1801,6 +1801,7 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 	}
 
 	mutex_unlock(&conn->chan_lock);
+	hci_chan_del(conn->hchan);
 
 	if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT)
 		cancel_delayed_work_sync(&conn->info_timer);
@@ -1813,7 +1814,6 @@ static void l2cap_conn_free(struct kref *ref)
 {
 	struct l2cap_conn *conn = container_of(ref, struct l2cap_conn, ref);
 
-	hci_chan_del(conn->hchan);
 	hci_conn_put(conn->hcon);
 	kfree(conn);
 }
@@ -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);
 }