------------[ cut here ]------------
WARNING: CPU: 1 PID: 7618 at drivers/gpu/drm/vkms/vkms_crtc.c:97 vkms_get_vblank_timestamp+0x17d/0x1a0 drivers/gpu/drm/vkms/vkms_crtc.c:97
Modules linked in:
CPU: 1 UID: 0 PID: 7618 Comm: syz.1.377 Not tainted 6.15.0-rc2-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:vkms_get_vblank_timestamp+0x17d/0x1a0 drivers/gpu/drm/vkms/vkms_crtc.c:97
Code: ff df 80 3c 08 00 74 08 4c 89 f7 e8 0d 0e e5 fb 49 89 1e b0 01 5b 41 5c 41 5d 41 5e 41 5f 5d e9 a4 bf c7 fa e8 c4 d3 7a fb 90 <0f> 0b 90 eb e4 89 d9 80 e1 07 38 c1 0f 8c b9 fe ff ff 48 89 df e8
RSP: 0018:ffffc9000435f288 EFLAGS: 00010283
RAX: ffffffff8648816c RBX: 00000050aacee3b0 RCX: 0000000000080000
RDX: ffffc9000d65f000 RSI: 000000000000913a RDI: 000000000000913b
RBP: ffffc9000435f420 R08: ffffffff864880d1 R09: 1ffff110043fa4a2
R10: dffffc0000000000 R11: ffffffff86487ff0 R12: 00000050aacee3b0
R13: ffff888147ad7950 R14: 1ffff9200086be84 R15: ffff888025690028
FS:  00007f758a05a6c0(0000) GS:ffff888125093000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d331b1d950 CR3: 000000005d970000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 drm_crtc_get_last_vbltimestamp drivers/gpu/drm/drm_vblank.c:878 [inline]
 drm_crtc_next_vblank_start+0x257/0x4f0 drivers/gpu/drm/drm_vblank.c:1012
 set_fence_deadline drivers/gpu/drm/drm_atomic_helper.c:1596 [inline]
 drm_atomic_helper_wait_for_fences+0x27c/0x8e0 drivers/gpu/drm/drm_atomic_helper.c:1643
 drm_atomic_helper_commit+0x53f/0xa00 drivers/gpu/drm/drm_atomic_helper.c:2072
 drm_atomic_commit+0x298/0x2f0 drivers/gpu/drm/drm_atomic.c:1518
 drm_client_modeset_commit_atomic+0x677/0x7d0 drivers/gpu/drm/drm_client_modeset.c:1079
 drm_client_modeset_commit_locked+0xe0/0x520 drivers/gpu/drm/drm_client_modeset.c:1182
 pan_display_atomic drivers/gpu/drm/drm_fb_helper.c:1387 [inline]
 drm_fb_helper_pan_display+0x3e8/0xc20 drivers/gpu/drm/drm_fb_helper.c:1447
 fb_pan_display+0x3a5/0x680 drivers/video/fbdev/core/fbmem.c:191
 fb_set_var+0x821/0xfa0 drivers/video/fbdev/core/fbmem.c:323
 do_fb_ioctl+0x671/0x7e0 drivers/video/fbdev/core/fb_chrdev.c:90
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xf3/0x160 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f758918d169
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:00007f758a05a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f75893a6080 RCX: 00007f758918d169
RDX: 0000200000000380 RSI: 0000000000004601 RDI: 0000000000000004
RBP: 00007f758920e990 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f75893a6080 R15: 00007ffcc0c21848
 </TASK>