ALSA: usx2y: Use snd_card_free_when_closed() at disconnection

The USB disconnect callback is supposed to be short and not too-long
waiting.  OTOH, the current code uses snd_card_free() at
disconnection, but this waits for the close of all used fds, hence it
can take long.  It eventually blocks the upper layer USB ioctls, which
may trigger a soft lockup.

An easy workaround is to replace snd_card_free() with
snd_card_free_when_closed().  This variant returns immediately while
the release of resources is done asynchronously by the card device
release at the last close.

Fixes: 230cd5e24853 ("[ALSA] prevent oops & dead keyboard on usb unplugging while the device is be ing used")
Reported-by: syzbot+73582d08864d8268b6fd@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=73582d08864d8268b6fd
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20241113111042.15058-2-tiwai@suse.de

diff --git a/sound/usb/usx2y/usbusx2y.c b/sound/usb/usx2y/usbusx2y.c
index 2f9cede242b3a9a3a8e9e4b4d52c7ff8d3dafa36..5f81c68fd42b68f26709aaf47459eeb9988375d2 100644 (file)
--- a/sound/usb/usx2y/usbusx2y.c
+++ b/sound/usb/usx2y/usbusx2y.c
@@ -422,7 +422,7 @@ static void snd_usx2y_disconnect(struct usb_interface *intf)
        }
        if (usx2y->us428ctls_sharedmem)
                wake_up(&usx2y->us428ctls_wait_queue_head);
-       snd_card_free(card);
+       snd_card_free_when_closed(card);
 }
 
 static int snd_usx2y_probe(struct usb_interface *intf,