Patch "ALSA: line6: Fix missing initialization before error path" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

ALSA: line6: Fix missing initialization before error path

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
alsa-line6-fix-missing-initialization-before-error-path.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Takashi Iwai <[email protected]>
Date: Mon, 9 Oct 2017 14:32:15 +0200
Subject: ALSA: line6: Fix missing initialization before error path

From: Takashi Iwai <[email protected]>

commit cb02ffc76a53b5ea751b79b8d4f4d180e5868475 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 #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().

---
 sound/usb/line6/podhd.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

@@ -307,6 +307,9 @@ static int podhd_init(struct usb_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) {
 		/* create sysfs entries: */
 		err = snd_card_add_dev_attr(line6->card, &podhd_dev_attr_group);

@@ -330,8 +333,6 @@ static int podhd_init(struct usb_line6 *
 	}
 
 	/* init device and delay registering */
-	init_timer(&pod->startup_timer);
-	INIT_WORK(&pod->startup_work, podhd_startup_workqueue);
 	podhd_startup(pod);
 	return 0;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/alsa-line6-fix-missing-initialization-before-error-path.patch queue-4.9/alsa-caiaq-fix-stray-urb-at-probe-error-path.patch queue-4.9/alsa-seq-fix-copy_from_user-call-inside-lock.patch queue-4.9/alsa-seq-fix-use-after-free-at-creating-a-port.patch queue-4.9/alsa-line6-fix-leftover-urb-at-error-path-during-probe.patch queue-4.9/alsa-usb-audio-kill-stray-urb-at-exiting.patch