Re: x86: WARNING: kernel stack frame pointer in kworker has bad value

[Josh Poimboeuf]

On Mon, Jan 23, 2017 at 07:43:18PM +0100, Dmitry Vyukov wrote:
> Hello,
> 
> I am getting the following warnings while running syzkaller fuzzer on
> 7a308bb3016f57e5be11a677d15b821536419d36:
> 
> WARNING: kernel stack frame pointer at ffff880065f7fef8 in
> kworker/1:3:21075 has bad value ffffffff81598080
> unwind stack type:0 next_sp:          (null) mask:2 graph_idx:0
> ...
> 
> Here are 4 examples:
> 
> https://gist.githubusercontent.com/dvyukov/7258fca11e5c3db6e8f8fb684e6168ff/raw/2ca14f3c7294c7e466611f8ecfb3072c676a657c/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/cc442b144ae712f0e1bdeb065085e36a/raw/f713cef7e9689914fc94838a0a7d4192224fb6d2/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/9058cce2647e3d37157c283c6400498c/raw/7a8ec8d71b9e95eeb24156073eeef96ba61d95ea/gistfile1.txt
> https://gist.githubusercontent.com/dvyukov/b899dfa72d611b511a674b63676921f3/raw/90203ed26b6674dedba8c1c16dd76309ef21fbea/gistfile1.txt
> 
> Unfortunately this is not reproducible, but there is a stack dump, so
> maybe it's enough to figure out the root cause.

This seems like some kind of stack corruption.  Here are the stack
traces:

> https://gist.githubusercontent.com/dvyukov/7258fca11e5c3db6e8f8fb684e6168ff/raw/2ca14f3c7294c7e466611f8ecfb3072c676a657c/gistfile1.txt

  ffff8800520eef68: ffffffff812b148e (__save_stack_trace+0x6e/0xd0)
  ffff8800520eefe8: ffffffff812b1506 (save_stack_trace+0x16/0x20)
  ffff8800520eeff8: ffffffff81a0c843 (save_stack+0x43/0xd0)
  ffff8800520ef228: ffffffff81a0d17f (kasan_slab_free+0x6f/0xb0)
  ffff8800520ef250: ffffffff81a0a4e1 (kmem_cache_free+0x71/0x240)
  ffff8800520ef280: ffffffff822924d4 (ioc_release_fn+0x2e4/0x380)
  ffff8800520ef550: ffffffff814b4900 (process_one_work+0xbd0/0x1c10)
  ffff8800520ef9a8: ffffffff814b5b63 (worker_thread+0x223/0x1990)
  ffff8800520eff00: ffffffff814ce526 (kthread+0x326/0x3f0)

> https://gist.githubusercontent.com/dvyukov/cc442b144ae712f0e1bdeb065085e36a/raw/f713cef7e9689914fc94838a0a7d4192224fb6d2/gistfile1.txt

  ffff88005b40ef68: ffffffff812b260e (__save_stack_trace+0x6e/0xd0)
  ffff88005b40efe8: ffffffff812b2686 (save_stack_trace+0x16/0x20)
  ffff88005b40eff8: ffffffff81a0e8c3 (save_stack+0x43/0xd0)
  ffff88005b40f228: ffffffff81a0f1ff (kasan_slab_free+0x6f/0xb0)
  ffff88005b40f250: ffffffff81a0c561 (kmem_cache_free+0x71/0x240)
  ffff88005b40f280: ffffffff822943b4 (ioc_release_fn+0x2e4/0x380)
  ffff88005b40f550: ffffffff814b6980 (process_one_work+0xbd0/0x1c10)
  ffff88005b40f9a8: ffffffff814b7be3 (worker_thread+0x223/0x1990)
  ffff88005b40ff00: ffffffff814d05a6 (kthread+0x326/0x3f0)

> https://gist.githubusercontent.com/dvyukov/9058cce2647e3d37157c283c6400498c/raw/7a8ec8d71b9e95eeb24156073eeef96ba61d95ea/gistfile1.txt

  ffff880065f7ef68: ffffffff812b260e (__save_stack_trace+0x6e/0xd0)
  ffff880065f7efe8: ffffffff812b2686 (save_stack_trace+0x16/0x20)
  ffff880065f7eff8: ffffffff81a0e8c3 (save_stack+0x43/0xd0)
  ffff880065f7f228: ffffffff81a0f1ff (kasan_slab_free+0x6f/0xb0)
  ffff880065f7f250: ffffffff81a0c561 (kmem_cache_free+0x71/0x240)
  ffff880065f7f280: ffffffff822943b4 (ioc_release_fn+0x2e4/0x380)
  ffff880065f7f550: ffffffff814b6980 (process_one_work+0xbd0/0x1c10)
  ffff880065f7f9a8: ffffffff814b7be3 (worker_thread+0x223/0x1990)
  ffff880065f7ff00: ffffffff814d05a6 (kthread+0x326/0x3f0)

> https://gist.githubusercontent.com/dvyukov/b899dfa72d611b511a674b63676921f3/raw/90203ed26b6674dedba8c1c16dd76309ef21fbea/gistfile1.txt

  ffff880065e57220: ffffffff812b148e (__save_stack_trace+0x6e/0xd0)
  ffff880065e572a0: ffffffff812b1506 (save_stack_trace+0x16/0x20)
  ffff880065e572b0: ffffffff81a0c843 (save_stack+0x43/0xd0)
  ffff880065e574e0: ffffffff81a0cb0a (kasan_kmalloc+0xaa/0xd0)
  ffff880065e57520: ffffffff81a0d102 (kasan_slab_alloc+0x12/0x20)
  ffff880065e57530: ffffffff81a08704 (kmem_cache_alloc+0xf4/0x680)
  ffff880065e57598: ffffffff823293b3 (ida_pre_get+0x1f3/0x3b0)
  ffff880065e57720: ffffffff823296d8 (ida_simple_get+0x168/0x320)
  ffff880065e578e8: ffffffff814ad926 (create_worker+0x96/0x620)
  ffff880065e579a8: ffffffff814b68ad (worker_thread+0xf6d/0x1990)
  ffff880065e57f00: ffffffff814ce526 (kthread+0x326/0x3f0)

In all four cases, the frame pointer pushed by worker_thread() is
somehow changed to be the address at the end of
debug_check_no_locks_freed():

  ffff880065f7fef8: ffffffff81598080 (debug_check_no_locks_freed+0x5c0/0x5c0)

Can you please share the following:

- The output of "grep ffffffff81598080 System.map"
- The .config file


-- 
Josh