syzbot


WARNING in drm_crtc_wait_one_vblank

Status: upstream: reported on 2025/12/25 00:33
Subsystems: dri
[Documentation on labels]
Reported-by: syzbot+c9f3062e1f1e68af836a@syzkaller.appspotmail.com
First crash: 15d, last: 2d06h
Discussions (2)
Title Replies (including bot) Last reply
[syzbot] Monthly dri report (Dec 2025) 0 (1) 2025/12/29 08:12
[syzbot] [dri?] WARNING in drm_crtc_wait_one_vblank 0 (1) 2025/12/25 00:33

Sample crash report:
------------[ cut here ]------------
faux_driver vkms: [drm] vblank wait timed out on crtc 0
WARNING: drivers/gpu/drm/drm_vblank.c:1320 at drm_crtc_wait_one_vblank+0x33a/0x4f0 drivers/gpu/drm/drm_vblank.c:1320, CPU#0: kworker/0:4/5907
Modules linked in:
CPU: 0 UID: 0 PID: 5907 Comm: kworker/0:4 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events drm_fb_helper_damage_work
RIP: 0010:drm_crtc_wait_one_vblank+0x4a3/0x4f0 drivers/gpu/drm/drm_vblank.c:1320
Code: 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 4c 89 ef e8 ff ee e1 fc 4d 8b 7d 00 4c 89 e7 48 8b 74 24 18 4c 89 fa 44 89 f1 <67> 48 0f b9 3a 48 8b 7c 24 28 44 89 f6 e8 8b f6 ff ff b8 92 ff ff
RSP: 0018:ffffc900042df840 EFLAGS: 00010246
RAX: 1ffff11004a14800 RBX: 1ffff9200085bf10 RCX: 0000000000000000
RDX: ffffffff8c08f7a0 RSI: ffffffff8c0aa5c0 RDI: ffffffff8fced610
RBP: ffffc900042df948 R08: ffffffff8fc3d077 R09: 1ffffffff1f87a0e
R10: dffffc0000000000 R11: fffffbfff1f87a0f R12: ffffffff8fced610
R13: ffff8880250a4000 R14: 0000000000000000 R15: ffffffff8c08f7a0
FS:  0000000000000000(0000) GS:ffff8881259dc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000007ee34000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 drm_client_modeset_wait_for_vblank+0xc5/0xf0 drivers/gpu/drm/drm_client_modeset.c:1330
 drm_fb_helper_fb_dirty drivers/gpu/drm/drm_fb_helper.c:236 [inline]
 drm_fb_helper_damage_work+0xc9/0x710 drivers/gpu/drm/drm_fb_helper.c:271
 process_one_work+0x93a/0x15a0 kernel/workqueue.c:3279
 process_scheduled_works kernel/workqueue.c:3362 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3443
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
----------------
Code disassembly (best guess):
   0:	48 b9 00 00 00 00 00 	movabs $0xdffffc0000000000,%rcx
   7:	fc ff df
   a:	80 3c 08 00          	cmpb   $0x0,(%rax,%rcx,1)
   e:	74 08                	je     0x18
  10:	4c 89 ef             	mov    %r13,%rdi
  13:	e8 ff ee e1 fc       	call   0xfce1ef17
  18:	4d 8b 7d 00          	mov    0x0(%r13),%r15
  1c:	4c 89 e7             	mov    %r12,%rdi
  1f:	48 8b 74 24 18       	mov    0x18(%rsp),%rsi
  24:	4c 89 fa             	mov    %r15,%rdx
  27:	44 89 f1             	mov    %r14d,%ecx
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	48 8b 7c 24 28       	mov    0x28(%rsp),%rdi
  34:	44 89 f6             	mov    %r14d,%esi
  37:	e8 8b f6 ff ff       	call   0xfffff6c7
  3c:	b8                   	.byte 0xb8
  3d:	92                   	xchg   %eax,%edx
  3e:	ff                   	(bad)
  3f:	ff                   	.byte 0xff

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/03 00:31 linux-next cc3aa43b44bd d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in drm_crtc_wait_one_vblank
2025/12/30 12:49 linux-next cc3aa43b44bd d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in drm_crtc_wait_one_vblank
2025/12/21 00:23 linux-next cc3aa43b44bd d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in drm_crtc_wait_one_vblank
* Struck through repros no longer work on HEAD.