ALSA: line6: Fix missing initialization before error path

BugLink: http://bugs.launchpad.net/bugs/1724669

commit cb02ffc upstream.

The error path in podhd_init() tries to clear the pending timer, while
the timer object is initialized at the end of init sequence, thus it
may hit the uninitialized object, as spotted by syzkaller:

  INFO: trying to register non-static key.
  the code is fine but needs lockdep annotation.
  turning off the locking correctness validator.
  CPU: 1 PID: 1845 Comm: kworker/1:2 Not tainted
  4.14.0-rc2-42613-g1488251d1a98 torvalds#238
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Workqueue: usb_hub_wq hub_event
  Call Trace:
   __dump_stack lib/dump_stack.c:16
   dump_stack+0x292/0x395 lib/dump_stack.c:52
   register_lock_class+0x6c4/0x1a00 kernel/locking/lockdep.c:769
   __lock_acquire+0x27e/0x4550 kernel/locking/lockdep.c:3385
   lock_acquire+0x259/0x620 kernel/locking/lockdep.c:4002
   del_timer_sync+0x12c/0x280 kernel/time/timer.c:1237
   podhd_disconnect+0x8c/0x160 sound/usb/line6/podhd.c:299
   line6_probe+0x844/0x1310 sound/usb/line6/driver.c:783
   podhd_probe+0x64/0x70 sound/usb/line6/podhd.c:474
   ....

For addressing it, assure the initializations of timer and work by
moving them to the beginning of podhd_init().

Fixes: 790869d ("ALSA: line6: Add support for POD X3")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

sound/usb/line6/podhd.c

@@ -318,6 +318,9 @@ static int podhd_init(struct usb_line6 *line6,
 
 	line6->disconnect = podhd_disconnect;
 
+	init_timer(&pod->startup_timer);
+	INIT_WORK(&pod->startup_work, podhd_startup_workqueue);
+
 	if (pod->line6.properties->capabilities & LINE6_CAP_CONTROL) {
 		/* claim the data interface */
 		intf = usb_ifnum_to_if(line6->usbdev,
@@ -359,8 +362,6 @@ static int podhd_init(struct usb_line6 *line6,
 	}
 
 	/* init device and delay registering */
-	init_timer(&pod->startup_timer);
-	INIT_WORK(&pod->startup_work, podhd_startup_workqueue);
 	podhd_startup(pod);
 	return 0;
 }