linux-kernel - Re: [syzbot] [bluetooth?] WARNING in hci_conn_set

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Date: Sun, 14 Apr 2024 16:30:44 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+d6282a21a27259b5f7e7@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bluetooth?] WARNING in hci_conn_set_handle

On Sat, 13 Apr 2024 23:05:32 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    480e035fc4c7 Merge tag 'drm-next-2024-03-13' of https://gi..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=162d4723180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  480e035fc4c7

--- x/net/bluetooth/hci_event.c
+++ y/net/bluetooth/hci_event.c
@@ -6902,7 +6902,7 @@ static void hci_le_create_big_complete_e
 					   struct sk_buff *skb)
 {
 	struct hci_evt_le_create_big_complete *ev = data;
-	struct hci_conn *conn;
+	struct hci_conn *conn, *next;
 	__u8 i = 0;
 
 	BT_DBG("%s status 0x%2.2x", hdev->name, ev->status);
@@ -6912,38 +6912,29 @@ static void hci_le_create_big_complete_e
 		return;
 
 	hci_dev_lock(hdev);
-	rcu_read_lock();
-
 	/* Connect all BISes that are bound to the BIG */
-	list_for_each_entry_rcu(conn, &hdev->conn_hash.list, list) {
+	list_for_each_entry_safe(conn, next, &hdev->conn_hash.list, list) {
 		if (bacmp(&conn->dst, BDADDR_ANY) ||
 		    conn->type != ISO_LINK ||
 		    conn->iso_qos.bcast.big != ev->handle)
 			continue;
 
-		if (hci_conn_set_handle(conn,
-					__le16_to_cpu(ev->bis_handle[i++])))
+		if (hci_conn_set_handle(conn, __le16_to_cpu(ev->bis_handle[i++])))
 			continue;
 
 		if (!ev->status) {
 			conn->state = BT_CONNECTED;
 			set_bit(HCI_CONN_BIG_CREATED, &conn->flags);
-			rcu_read_unlock();
 			hci_debugfs_create_conn(conn);
 			hci_conn_add_sysfs(conn);
 			hci_iso_setup_path(conn);
-			rcu_read_lock();
 			continue;
 		}
 
 		hci_connect_cfm(conn, ev->status);
-		rcu_read_unlock();
 		hci_conn_del(conn);
-		rcu_read_lock();
 	}
 
-	rcu_read_unlock();
-
 	if (!ev->status && !i)
 		/* If no BISes have been connected for the BIG,
 		 * terminate. This is in case all bound connections
@@ -6952,7 +6943,6 @@ static void hci_le_create_big_complete_e
 		 */
 		hci_cmd_sync_queue(hdev, hci_iso_term_big_sync,
 				   UINT_PTR(ev->handle), NULL);
-
 	hci_dev_unlock(hdev);
 }
 
--