Subject: Re: usb/net/p54: trying to register non-static key in p54_unregister_leds

From: Christian Lamparter <[email-masked]>
Date: Wed, 20 Sep 2017 21:27:42 +0200

On Wednesday, September 20, 2017 8:37:08 PM CEST Andrey Konovalov wrote:
> Hi!
> 
> I've got the following report while fuzzing the kernel with syzkaller.
> 
> On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).
> 
> INFO: trying to register non-static key.
> the code is fine but needs lockdep annotation.
> turning off the locking correctness validator.
> CPU: 1 PID: 1404 Comm: kworker/1:1 Not tainted
> 4.14.0-rc1-42251-gebb2c2437d80-dirty #205
> 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
>  flush_work+0xf0/0x8c0 kernel/workqueue.c:2886
>  __cancel_work_timer+0x51d/0x870 kernel/workqueue.c:2961
>  cancel_delayed_work_sync+0x1f/0x30 kernel/workqueue.c:3081
>  p54_unregister_leds+0x6c/0xc0 drivers/net/wireless/intersil/p54/led.c:160
>  p54_unregister_common+0x3d/0xb0 drivers/net/wireless/intersil/p54/main.c:856
>  p54u_disconnect+0x86/0x120 drivers/net/wireless/intersil/p54/p54usb.c:1073
>  usb_unbind_interface+0x21c/0xa90 drivers/usb/core/driver.c:423
>  __device_release_driver drivers/base/dd.c:861
>  device_release_driver_internal+0x4f4/0x5c0 drivers/base/dd.c:893
>  device_release_driver+0x1e/0x30 drivers/base/dd.c:918
>  bus_remove_device+0x2f4/0x4b0 drivers/base/bus.c:565
>  device_del+0x5c4/0xab0 drivers/base/core.c:1985
>  usb_disable_device+0x1e9/0x680 drivers/usb/core/message.c:1170
>  usb_disconnect+0x260/0x7a0 drivers/usb/core/hub.c:2124
>  hub_port_connect drivers/usb/core/hub.c:4754
>  hub_port_connect_change drivers/usb/core/hub.c:5009
>  port_event drivers/usb/core/hub.c:5115
>  hub_event+0x1318/0x3740 drivers/usb/core/hub.c:5195
>  process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
>  process_scheduled_works kernel/workqueue.c:2179
>  worker_thread+0xb2b/0x1850 kernel/workqueue.c:2255
>  kthread+0x3a1/0x470 kernel/kthread.c:231
>  ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431
> 

It seems this is caused as a result of:
    -> lock_map_acquire(&work->lockdep_map);
	    lock_map_release(&work->lockdep_map);

    in flush_work() [0]

This was added by:

	commit 0976dfc1d0cd80a4e9dfaf87bd8744612bde475a
	Author: Stephen Boyd <[email-masked]>
	Date:   Fri Apr 20 17:28:50 2012 -0700

	workqueue: Catch more locking problems with flush_work()
    
Looking at the Stephen's patch, it's clear that it was made
with "static DECLARE_WORK(work, my_work)" in mind. However
p54's led_work is "per-device", hence it is stored in the
devices context p54_common, which is dynamically allocated.
So, maybe revert Stephen's patch?

[0] <http://elixir.free-electrons.com/linux/latest/source/kernel/workqueue.c#L2853>