Date:   Tue, 03 Oct 2017 09:41:10 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     "Andrey Konovalov" <andreyknvl@...gle.com>
Cc:     <alsa-devel@...a-project.org>, "Andrej Krutak" <dev@...ree.sk>,
        "Jaroslav Kysela" <perex@...ex.cz>,
        "Hans P. Möller Ebner" 
        <hmoller@...cl>, "LKML" <linux-kernel@...r.kernel.org>,
        "Dmitry Vyukov" <dvyukov@...gle.com>,
        "Kostya Serebryany" <kcc@...gle.com>,
        "syzkaller" <syzkaller@...glegroups.com>
Subject: Re: usb/sound/line6: trying to register non-static key in podhd_disconnect

On Mon, 25 Sep 2017 14:40:08 +0200,
Andrey Konovalov wrote:
> 
> Hi!
> 
> I've got the following report while fuzzing the kernel with syzkaller.
> 
> On commit e19b205be43d11bff638cad4487008c48d21c103 (4.14-rc2).
> 
> 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
>  usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
>  really_probe drivers/base/dd.c:413
>  driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
>  __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
>  bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
>  __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
>  device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
>  bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
>  device_add+0xd0b/0x1660 drivers/base/core.c:1835
>  usb_set_configuration+0x104e/0x1870 drivers/usb/core/message.c:1932
>  generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
>  usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
>  really_probe drivers/base/dd.c:413
>  driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
>  __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
>  bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
>  __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
>  device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
>  bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
>  device_add+0xd0b/0x1660 drivers/base/core.c:1835
>  usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
>  hub_port_connect drivers/usb/core/hub.c:4903
>  hub_port_connect_change drivers/usb/core/hub.c:5009
>  port_event drivers/usb/core/hub.c:5115
>  hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
>  process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
>  worker_thread+0x221/0x1850 kernel/workqueue.c:2253
>  kthread+0x3a1/0x470 kernel/kthread.c:231
>  ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

This looks like an access to the uninitialized timer object.
Could you check the patch below whether it fixes the issue?
Thanks!


Takashi

-- 8< --
From: Takashi Iwai <tiwai@...e.de>
Subject: [PATCH] ALSA: line6: Fix missing initialization before error path

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().

Fixes: 790869dacc3d ("ALSA: line6: Add support for POD X3")
Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 sound/usb/line6/podhd.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sound/usb/line6/podhd.c b/sound/usb/line6/podhd.c
index 956f847a96e4..14ab82ea7e82 100644
--- a/sound/usb/line6/podhd.c
+++ b/sound/usb/line6/podhd.c
@@ -317,6 +317,9 @@ 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,
@@ -358,8 +361,6 @@ 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;
 }
-- 
2.14.2

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