Re: [syzbot] [net?] KASAN: slab-use-after-free Read in handle_tx (2)

[Hillf Danton <hdanton@sina.com>]

On Fri, 17 Jan 2025 09:11:25 -0800
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    9bffa1ad25b8 Merge tag 'drm-fixes-2025-01-17' of https://g..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17d6c2b0580000

#syz test

--- x/drivers/net/caif/caif_serial.c
+++ y/drivers/net/caif/caif_serial.c
@@ -304,11 +304,14 @@ static void ser_release(struct work_stru
 	spin_unlock(&ser_lock);
 
 	if (!list_empty(&list)) {
+		struct tty_struct *tty;
 		rtnl_lock();
 		list_for_each_entry_safe(ser, tmp, &list, node) {
+			tty = ser->tty;
 			dev_close(ser->dev);
 			unregister_netdevice(ser->dev);
 			debugfs_deinit(ser);
+			tty_kref_put(tty);
 		}
 		rtnl_unlock();
 	}
@@ -369,8 +372,6 @@ static void ldisc_close(struct tty_struc
 {
 	struct ser_device *ser = tty->disc_data;
 
-	tty_kref_put(ser->tty);
-
 	spin_lock(&ser_lock);
 	list_move(&ser->node, &ser_release_list);
 	spin_unlock(&ser_lock);
--