From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	syzbot+d8f72178ab6783a7daea@syzkaller.appspotmail.com,
	Takashi Iwai <tiwai@suse.de>,
	Johnny Hao <johnny_haocn@sina.com>
Subject: [PATCH 6.1 369/481] ALSA: usb-audio: Kill timer properly at removal
Date: Mon, 23 Mar 2026 14:45:51 +0100
Message-ID: <20260323134534.120863417@linuxfoundation.org>
In-Reply-To: <20260323134525.256603107@linuxfoundation.org>
References: <20260323134525.256603107@linuxfoundation.org>
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6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

[ Upstream commit 0718a78f6a9f04b88d0dc9616cc216b31c5f3cf1 ]

The USB-audio MIDI code initializes the timer, but in a rare case, the
driver might be freed without the disconnect call.  This leaves the
timer in an active state while the assigned object is released via
snd_usbmidi_free(), which ends up with a kernel warning when the debug
configuration is enabled, as spotted by fuzzer.

For avoiding the problem, put timer_shutdown_sync() at
snd_usbmidi_free(), so that the timer can be killed properly.
While we're at it, replace the existing timer_delete_sync() at the
disconnect callback with timer_shutdown_sync(), too.

Reported-by: syzbot+d8f72178ab6783a7daea@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/681c70d7.050a0220.a19a9.00c6.GAE@google.com
Cc: <stable@vger.kernel.org>
Link: https://patch.msgid.link/20250519212031.14436-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[ The context change is due to the commit 8fa7292fee5c
("treewide: Switch/rename to timer_delete[_sync]()")
in v6.15 which is irrelevant to the logic of this patch. ]
Signed-off-by: Johnny Hao <johnny_haocn@sina.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 sound/usb/midi.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -1530,6 +1530,7 @@ static void snd_usbmidi_free(struct snd_
 			snd_usbmidi_in_endpoint_delete(ep->in);
 	}
 	mutex_destroy(&umidi->mutex);
+	timer_shutdown_sync(&umidi->error_timer);
 	kfree(umidi);
 }
 
@@ -1553,7 +1554,7 @@ void snd_usbmidi_disconnect(struct list_
 	spin_unlock_irq(&umidi->disc_lock);
 	up_write(&umidi->disc_rwsem);
 
-	del_timer_sync(&umidi->error_timer);
+	timer_shutdown_sync(&umidi->error_timer);
 
 	for (i = 0; i < MIDI_MAX_ENDPOINTS; ++i) {
 		struct snd_usb_midi_endpoint *ep = &umidi->endpoints[i];