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Date:   Sun, 24 Feb 2019 12:40:19 -0800 (PST)
From:   David Rientjes <rientjes@google.com>
To:     syzbot <syzbot+12f1b031b6da017e34f8@syzkaller.appspotmail.com>
cc:     airlied@linux.ie, daniel@ffwll.ch, dri-devel@lists.freedesktop.org,
        hamohammed.sa@gmail.com, linux-kernel@vger.kernel.org,
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        rodrigosiqueiramelo@gmail.com, seanpaul@chromium.org,
        syzkaller-bugs@googlegroups.com
Subject: Re: INFO: trying to register non-static key in __flush_work
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On Sat, 29 Dec 2018, syzbot wrote:

> 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@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 is reproducible up to at least

commit e60b5f79bd7529e76b13cf1e85823abbd0e33634
Merge: 6089a91fc02e 8f5b27347e88
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat Feb 23 11:13:50 2019 -0800

    Merge tag 'powerpc-5.0-6' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

and my theory is that it's due to this:

commit dfb9f5cabfe31b8e936b725b5de8f787f7c18b0f
Author: Haneen Mohammed <hamohammed.sa@gmail.com>
Date:   Tue Jul 24 19:31:05 2018 +0300

    drm/vkms: subclass CRTC state
    
in 4.20-rc1.  We aren't doing INIT_WORK() for the workqueue that is being 
flushed.

Don't we need to do INIT_WORK() in vkms_atomic_crtc_reset() too?