Hello, syzbot found the following issue on:
HEAD commit: f0b9d8eb98df Merge tag 'nfsd-6.19-3' of git://git.kernel.o.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17ea1074580000 kernel config: https://syzkaller.appspot.com/x/.config?x=1f2b6fe1fdf1a00b dashboard link: https://syzkaller.appspot.com/bug?extid=f59157955aba9d0cb43b compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10706922580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f89f92580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/200586687016/disk-f0b9d8eb.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/d56481335522/vmlinux-f0b9d8eb.xz kernel image: https://storage.googleapis.com/syzbot-assets/12cfd8855d89/bzImage-f0b9d8eb.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:1318 at drm_wait_one_vblank+0x39a/0x5c0 drivers/gpu/drm/drm_vblank.c:1318, CPU#0: kworker/0:0/9 Modules linked in: CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: events drm_fb_helper_damage_work RIP: 0010:drm_wait_one_vblank+0x587/0x5c0 drivers/gpu/drm/drm_vblank.c:1318 Code: 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 4c 89 ef e8 ba c8 f6 fc 4d 8b 7d 00 48 89 df 4c 89 e6 4c 89 fa 8b 4c 24 04 <67> 48 0f b9 3a e9 d5 fc ff ff 44 89 f9 80 e1 07 80 c1 03 38 c1 0f RSP: 0018:ffffc900000e7860 EFLAGS: 00010246 RAX: 1ffff110281e8400 RBX: ffffffff8ee5ae70 RCX: 0000000000000000 RDX: ffffffff8b569b80 RSI: ffffffff8b584ca0 RDI: ffffffff8ee5ae70 RBP: ffffc900000e7948 R08: 0000000000000000 R09: 0000000000000000 R10: dffffc0000000000 R11: fffffbfff1db66af R12: ffffffff8b584ca0 R13: ffff888140f42000 R14: 1ffff9200001cf10 R15: ffffffff8b569b80 FS: 0000000000000000(0000) GS:ffff888126cef000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055557a9da5c8 CR3: 0000000043562000 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:334 [inline] drm_fb_helper_damage_work+0xc9/0x650 drivers/gpu/drm/drm_fb_helper.c:369 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 </TASK> ---------------- Code disassembly (best guess), 1 bytes skipped: 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 ba c8 f6 fc call 0xfcf6c8d2 18: 4d 8b 7d 00 mov 0x0(%r13),%r15 1c: 48 89 df mov %rbx,%rdi 1f: 4c 89 e6 mov %r12,%rsi 22: 4c 89 fa mov %r15,%rdx 25: 8b 4c 24 04 mov 0x4(%rsp),%ecx * 29: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction 2e: e9 d5 fc ff ff jmp 0xfffffd08 33: 44 89 f9 mov %r15d,%ecx 36: 80 e1 07 and $0x7,%cl 39: 80 c1 03 add $0x3,%cl 3c: 38 c1 cmp %al,%cl 3e: 0f .byte 0xf --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at [email protected]. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title 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. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup
