usb: iowarrior: fix deadlock on disconnect

commit c468a8aa790e0dfe0a7f8a39db282d39c2c00b46 upstream.

We have to drop the mutex before we close() upon disconnect()
as close() needs the lock. This is safe to do by dropping the
mutex as intfdata is already set to NULL, so open() will fail.

Fixes: 03f36e88 ("USB: open disconnect race in iowarrior")
Reported-by:  <syzbot+a64a382964bf6c71a9c0@syzkaller.appspotmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20190808092728.23417-1-oneukum@suse.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>