syzbot has found a reproducer for the following issue on: HEAD commit: 6de23f81a5e0 Linux 7.0-rc1 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1240455a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=d91443204e48b7a1 dashboard link: https://syzkaller.appspot.com/bug?extid=c9f3062e1f1e68af836a compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14ffc152580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=147dd9e6580000
Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/8c986068e2b3/disk-6de23f81.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/15bbf2602cdc/vmlinux-6de23f81.xz kernel image: https://storage.googleapis.com/syzbot-assets/5e9cae7959ff/bzImage-6de23f81.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: [email protected] ------------[ 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+0x357/0x500 drivers/gpu/drm/drm_vblank.c:1320, CPU#0: kworker/0:4/5856 Modules linked in: CPU: 0 UID: 0 PID: 5856 Comm: kworker/0:4 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Workqueue: events drm_fb_helper_damage_work RIP: 0010:drm_crtc_wait_one_vblank+0x4b6/0x500 drivers/gpu/drm/drm_vblank.c:1320 Code: e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 4c 89 ef e8 8a d9 d4 fc 4d 8b 7d 00 48 89 df 4c 89 e6 4c 89 fa 44 89 f1 <67> 48 0f b9 3a 48 8b 3c 24 44 89 f6 e8 e9 f4 ff ff b8 92 ff ff ff RSP: 0018:ffffc90004b878e0 EFLAGS: 00010246 RAX: 1ffff11004a21800 RBX: ffffffff8f7504f0 RCX: 0000000000000000 RDX: ffffffff8bbf2ce0 RSI: ffffffff8bc0ebe0 RDI: ffffffff8f7504f0 RBP: ffffc90004b879c8 R08: 0000000000000000 R09: 0000000000000000 R10: dffffc0000000000 R11: fffffbfff1ed44b7 R12: ffffffff8bc0ebe0 R13: ffff88802510c000 R14: 0000000000000000 R15: ffffffff8bbf2ce0 FS: 0000000000000000(0000) GS:ffff888126343000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f3c5d8c9d40 CR3: 00000000247e0000 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+0x131/0x6f0 drivers/gpu/drm/drm_fb_helper.c:274 process_one_work kernel/workqueue.c:3275 [inline] process_scheduled_works+0xb02/0x1830 kernel/workqueue.c:3358 worker_thread+0xa50/0xfc0 kernel/workqueue.c:3439 kthread+0x388/0x470 kernel/kthread.c:467 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> ---------------- Code disassembly (best guess): 0: e8 03 48 b9 00 call 0xb94808 5: 00 00 add %al,(%rax) 7: 00 00 add %al,(%rax) 9: fc cld a: ff lcall (bad) b: df 80 3c 08 00 74 filds 0x7400083c(%rax) 11: 08 4c 89 ef or %cl,-0x11(%rcx,%rcx,4) 15: e8 8a d9 d4 fc call 0xfcd4d9a4 1a: 4d 8b 7d 00 mov 0x0(%r13),%r15 1e: 48 89 df mov %rbx,%rdi 21: 4c 89 e6 mov %r12,%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 3c 24 mov (%rsp),%rdi 33: 44 89 f6 mov %r14d,%esi 36: e8 e9 f4 ff ff call 0xfffff524 3b: b8 92 ff ff ff mov $0xffffff92,%eax --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.
