INFO: trying to register non-static key in __flush_work

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    5694cecdb092 Merge tag 'arm64-upstream' of git://git.kerne..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=124eebc7400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=91a256823ef17263
dashboard link: https://syzkaller.appspot.com/bug?extid=12f1b031b6da017e34f8
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1174a1dd400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1336e38b400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+12f1b031b6da017e34f8 at syzkaller.appspotmail.com

INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
CPU: 0 PID: 8039 Comm: syz-executor964 Not tainted 4.20.0+ #389
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1d3/0x2c6 lib/dump_stack.c:113
  assign_lock_key kernel/locking/lockdep.c:727 [inline]
  register_lock_class+0x21c5/0x29d0 kernel/locking/lockdep.c:753
  __lock_acquire+0x184/0x4c20 kernel/locking/lockdep.c:3227
  lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
  __flush_work+0x752/0x9b0 kernel/workqueue.c:2912
  flush_work+0x17/0x20 kernel/workqueue.c:2938
  vkms_atomic_crtc_destroy_state+0x2b/0x40  
drivers/gpu/drm/vkms/vkms_crtc.c:139
  drm_atomic_state_default_clear+0x37c/0xda0 drivers/gpu/drm/drm_atomic.c:171
  drm_atomic_state_clear+0x9f/0xd0 drivers/gpu/drm/drm_atomic.c:240
  __drm_atomic_state_free+0x3a/0xf0 drivers/gpu/drm/drm_atomic.c:256
  kref_put include/linux/kref.h:70 [inline]
  drm_atomic_state_put include/drm/drm_atomic.h:385 [inline]
  drm_atomic_helper_set_config+0xe6/0x160  
drivers/gpu/drm/drm_atomic_helper.c:2947
  drm_mode_setcrtc+0x767/0x1890 drivers/gpu/drm/drm_crtc.c:748
  drm_ioctl_kernel+0x278/0x330 drivers/gpu/drm/drm_ioctl.c:758
  drm_ioctl+0x58f/0xb90 drivers/gpu/drm/drm_ioctl.c:858
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:509 [inline]
  do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
  ksys_ioctl+0xa9/0xd0 fs/ioctl.c:713
  __do_sys_ioctl fs/ioctl.c:720 [inline]
  __se_sys_ioctl fs/ioctl.c:718 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x443e59
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 7b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff2bc037c8 EFLAGS: 00000213 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004002e0 RCX: 0000000000443e59
RDX: 0000000020000100 RSI: 00000000c06864a2 RDI: 0000000000000003
RBP: 00000000006ce018 R08: 0000000000000000 R09: 00000000004002e0
R10: 000000000000000f R11: 0000000000000213 R12: 0000000000401b60
R13: 0000000000401bf0 R14: 0000000000000000 R15: 000000000


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller at googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches