------------[ cut here ]------------
WARNING: CPU: 0 PID: 5360 at drivers/gpu/drm/vkms/vkms_crtc.c:97 vkms_get_vblank_timestamp+0x137/0x160 drivers/gpu/drm/vkms/vkms_crtc.c:97
Modules linked in:
CPU: 0 UID: 0 PID: 5360 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:vkms_get_vblank_timestamp+0x137/0x160 drivers/gpu/drm/vkms/vkms_crtc.c:97
Code: 42 80 3c 28 00 74 08 48 89 df e8 44 ab 29 fc 4c 89 33 b0 01 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 1a ae c4 fb 90 <0f> 0b 90 eb e3 44 89 e1 80 e1 07 38 c1 0f 8c ff fe ff ff 4c 89 e7
RSP: 0018:ffffc9000d32f148 EFLAGS: 00010246
RAX: ffffffff85fb1c86 RBX: ffffc9000d32f2c0 RCX: 0000000000100000
RDX: ffffc9000e05a000 RSI: 00000000000fffff RDI: 0000000000100000
RBP: 1ffff92001a65e58 R08: ffffc90001a29000 R09: 0000000000000000
R10: ffffc90001a29000 R11: ffffffff85fb1b50 R12: 000000141f118b2b
R13: dffffc0000000000 R14: ffff888032540028 R15: 000000141f118b2b
FS:  00007f89c94416c0(0000) GS:ffff88808d007000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000008000 CR3: 0000000034866000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 drm_crtc_get_last_vbltimestamp drivers/gpu/drm/drm_vblank.c:879 [inline]
 drm_crtc_next_vblank_start+0x223/0x470 drivers/gpu/drm/drm_vblank.c:1013
 set_fence_deadline drivers/gpu/drm/drm_atomic_helper.c:1711 [inline]
 drm_atomic_helper_wait_for_fences+0x265/0x8c0 drivers/gpu/drm/drm_atomic_helper.c:1758
 drm_atomic_helper_commit+0x5c7/0xb10 drivers/gpu/drm/drm_atomic_helper.c:2187
 drm_atomic_commit+0x262/0x2c0 drivers/gpu/drm/drm_atomic.c:1577
 drm_client_modeset_commit_atomic+0x620/0x760 drivers/gpu/drm/drm_client_modeset.c:1103
 drm_client_modeset_commit_locked+0xcb/0x4d0 drivers/gpu/drm/drm_client_modeset.c:1206
 pan_display_atomic drivers/gpu/drm/drm_fb_helper.c:1388 [inline]
 drm_fb_helper_pan_display+0x3e7/0xbd0 drivers/gpu/drm/drm_fb_helper.c:1448
 fb_pan_display+0x39b/0x680 drivers/video/fbdev/core/fbmem.c:193
 bit_update_start+0x4d/0x1e0 drivers/video/fbdev/core/bitblit.c:380
 fbcon_switch+0x1568/0x2040 drivers/video/fbdev/core/fbcon.c:2206
 redraw_screen+0x56a/0xe90 drivers/tty/vt/vt.c:965
 con2fb_init_display drivers/video/fbdev/core/fbcon.c:828 [inline]
 set_con2fb_map+0xb43/0x13c0 drivers/video/fbdev/core/fbcon.c:902
 fbcon_set_con2fb_map_ioctl+0x18a/0x1f0 drivers/video/fbdev/core/fbcon.c:3139
 do_fb_ioctl+0x3df/0x750 drivers/video/fbdev/core/fb_chrdev.c:138
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f89c858eec9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f89c9441038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f89c87e5fa0 RCX: 00007f89c858eec9
RDX: 00002000000000c0 RSI: 0000000000004610 RDI: 000000000000000a
RBP: 00007f89c8611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f89c87e6038 R14: 00007f89c87e5fa0 R15: 00007ffc9a40e0f8
 </TASK>