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

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Message-Id: <20240312112003.2116-1-hdanton@sina.com>
Date: Tue, 12 Mar 2024 19:20:03 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+2a81fdd5c6ddffee3894@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [serial?] KASAN: slab-use-after-free Read in tty_write_room (2)

On Mon, 11 Mar 2024 07:34:21 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    e8f897f4afef Linux 6.8
> git tree:       upstream
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11f338d1180000

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

--- x/drivers/net/caif/caif_serial.c
+++ y/drivers/net/caif/caif_serial.c
@@ -306,8 +306,11 @@ static void ser_release(struct work_stru
 	if (!list_empty(&list)) {
 		rtnl_lock();
 		list_for_each_entry_safe(ser, tmp, &list, node) {
+			struct tty_struct *tty = ser->tty;
+
 			dev_close(ser->dev);
 			unregister_netdevice(ser->dev);
+			tty_kref_put(tty);
 			debugfs_deinit(ser);
 		}
 		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);
--