Re: [syzbot] [sound?] INFO: task hung in snd_card_free
From: Edward Adam Davis
Date: Tue Nov 05 2024 - 20:37:32 EST
1. snd ctrl will add card_dev ref count and can't call close to dec it,
it is waiting for 2 to release usb dev lock.
2. usb dev lock has been locked by hung task (here is usb_disconnect), it waiting 1
to exit and release card_dev.
#syz test
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 3beb6a862e80..dd037dc4cb37 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -2605,7 +2605,8 @@ static long usbdev_do_ioctl(struct file *file, unsigned int cmd,
if (!(file->f_mode & FMODE_WRITE))
return -EPERM;
- usb_lock_device(dev);
+ if (!usb_trylock_device(dev))
+ return -EBUSY;
/* Reap operations are allowed even after disconnection */
switch (cmd) {