linux-kernel - Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Read in l2cap

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Message-Id: <20240908133747.2610-1-hdanton@sina.com>
Date: Sun,  8 Sep 2024 21:37:47 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+c12e2f941af1feb5632c@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Read in l2cap_connect (2)

On Sat, 07 Sep 2024 07:42:26 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    788220eee30d Merge tag 'pm-6.11-rc7' of git://git.kernel.o..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1304189f980000

#syz test

--- x/net/bluetooth/hci_core.c
+++ y/net/bluetooth/hci_core.c
@@ -3782,13 +3782,18 @@ static void hci_acldata_packet(struct hc
 
 	hci_dev_lock(hdev);
 	conn = hci_conn_hash_lookup_handle(hdev, handle);
+	if (conn)
+		hci_conn_get(conn);
 	hci_dev_unlock(hdev);
 
 	if (conn) {
 		hci_conn_enter_active_mode(conn, BT_POWER_FORCE_ACTIVE_OFF);
 
+		hci_req_sync_lock(hdev);
 		/* Send to upper protocol */
 		l2cap_recv_acldata(conn, skb, flags);
+		hci_req_sync_unlock(hdev);
+		hci_conn_put(conn);
 		return;
 	} else {
 		bt_dev_err(hdev, "ACL packet for unknown connection handle %d",
--