[PATCH] usb: fix a task hung in snd_card_free

[Edward Adam Davis]

task 1: snd ctrl will add card_dev ref count and can't call close to dec it,
        it is blocked waiting for task 2 to release the USB dev lock.

task 2: usb dev lock has been locked by hung task (here is usb_disconnect),
        it is hung waiting for task 1 to exit and release card_dev.

Adjust the USB lock acquisition method to non-blocking in ioctl to avoid
hang when the USB connection is closed.

Reported-and-tested-by: syzbot+73582d08864d8268b6fd@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=73582d08864d8268b6fd
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
 drivers/usb/core/devio.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

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) {
-- 
2.43.0