linux-kernel - [syzbot] [dri?] WARNING in drm_crtc_wait_one

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Message-ID: <694c864d.050a0220.35954c.002e.GAE@google.com>
Date: Wed, 24 Dec 2025 16:33:17 -0800
From: syzbot <syzbot+c9f3062e1f1e68af836a@...kaller.appspotmail.com>
To: airlied@...il.com, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, maarten.lankhorst@...ux.intel.com, 
	mripard@...nel.org, simona@...ll.ch, syzkaller-bugs@...glegroups.com, 
	tzimmermann@...e.de
Subject: [syzbot] [dri?] WARNING in drm_crtc_wait_one_vblank

Hello,

syzbot found the following issue on:

HEAD commit:    cc3aa43b44bd Add linux-next specific files for 20251219
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=175fb77c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f7a09bf3b9133d9d
dashboard link: https://syzkaller.appspot.com/bug?extid=c9f3062e1f1e68af836a
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b1b23d9783ee/disk-cc3aa43b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/07451939cf74/vmlinux-cc3aa43b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e5ddf385746f/bzImage-cc3aa43b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c9f3062e1f1e68af836a@...kaller.appspotmail.com

------------[ 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#1: kworker/1:2/19751
Modules linked in:
CPU: 1 UID: 0 PID: 19751 Comm: kworker/1:2 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:ffffc9000bc1f840 EFLAGS: 00010246
RAX: 1ffff11004a3da00 RBX: 1ffff92001783f10 RCX: 0000000000000000
RDX: ffffffff8c08f7a0 RSI: ffffffff8c0aa5c0 RDI: ffffffff8fced610
RBP: ffffc9000bc1f948 R08: ffffffff8fc3d077 R09: 1ffffffff1f87a0e
R10: dffffc0000000000 R11: fffffbfff1f87a0f R12: ffffffff8fced610
R13: ffff8880251ed000 R14: 0000000000000000 R15: ffffffff8c08f7a0
FS:  0000000000000000(0000) GS:ffff888125adc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005627ed0d9b20 CR3: 000000002e21a000 CR4: 00000000003526f0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000083
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
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


---
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