[syzbot] [dri?] WARNING in drm_fbdev_shmem_helper_fb_dirty

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a59f57e2aa12 Merge tag 'watchdog-for-v7.2-rc7' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1328c2c6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a59830cba91a1981
dashboard link: https://syzkaller.appspot.com/bug?extid=369ee6a6e9d0bbf14b37
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-a59f57e2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3b0b58b842b2/vmlinux-a59f57e2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/48759b65e153/bzImage-a59f57e2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+369ee6...@syzkaller.appspotmail.com

FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 100, space 0, times 1
CPU: 0 UID: 0 PID: 805 Comm: kworker/0:2 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events drm_fb_helper_damage_work
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
fail_dump lib/fault-inject.c:73 [inline]
should_fail_ex+0x40c/0x560 lib/fault-inject.c:174
should_failslab+0xa8/0x100 mm/failslab.c:46
slab_pre_alloc_hook mm/slub.c:4539 [inline]
slab_alloc_node mm/slub.c:4897 [inline]
__kmalloc_cache_noprof+0xa8/0x660 mm/slub.c:5485
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
drm_atomic_commit_alloc+0xa9/0x100 drivers/gpu/drm/drm_atomic.c:178
drm_atomic_helper_dirtyfb+0x129/0xfd0 drivers/gpu/drm/drm_damage_helper.c:128
drm_fbdev_shmem_helper_fb_dirty+0x160/0x310 drivers/gpu/drm/drm_fbdev_shmem.c:117
drm_fb_helper_fb_dirty drivers/gpu/drm/drm_fb_helper.c:339 [inline]
drm_fb_helper_damage_work+0x84c/0xf20 drivers/gpu/drm/drm_fb_helper.c:365
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
------------[ cut here ]------------
virtio-pci 0000:00:01.0: [drm] Dirty helper failed: ret=-12
WARNING: drivers/gpu/drm/drm_fbdev_shmem.c:118 at drm_fbdev_shmem_helper_fb_dirty+0x1e1/0x310 drivers/gpu/drm/drm_fbdev_shmem.c:118, CPU#0: kworker/0:2/805
Modules linked in:
CPU: 0 UID: 0 PID: 805 Comm: kworker/0:2 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events drm_fb_helper_damage_work
RIP: 0010:drm_fbdev_shmem_helper_fb_dirty+0x288/0x310 drivers/gpu/drm/drm_fbdev_shmem.c:118
Code: 35 fc 4c 89 f8 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 ff e8 da 5b a4 fc 4d 8b 27 48 89 df 4c 89 f6 4c 89 e2 8b 5c 24 04 89 d9 <67> 48 0f b9 3a 89 d8 e9 f7 fe ff ff 89 d9 80 e1 07 fe c1 38 c1 0f
RSP: 0018:ffffc90003ebf8b8 EFLAGS: 00010246
RAX: 1ffff11003f0801a RBX: 00000000fffffff4 RCX: 00000000fffffff4
RDX: ffff88801f64ce40 RSI: ffffffff8c57c700 RDI: ffffffff90638ce0
RBP: ffff88801d350008 R08: 0000000000000dc0 R09: 00000000ffffffff
R10: dffffc0000000000 R11: fffffbfff1d94963 R12: ffff88801f64ce40
R13: dffffc0000000000 R14: ffffffff8c57c700 R15: ffff88801f8400d0
FS: 0000000000000000(0000) GS:ffff88808c549000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2ef6a77218 CR3: 0000000033b08000 CR4: 0000000000352ef0
Call Trace:
<TASK>
drm_fb_helper_fb_dirty drivers/gpu/drm/drm_fb_helper.c:339 [inline]
drm_fb_helper_damage_work+0x84c/0xf20 drivers/gpu/drm/drm_fb_helper.c:365
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 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: 35 fc 4c 89 f8 xor $0xf8894cfc,%eax
5: 48 c1 e8 03 shr $0x3,%rax
9: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1)
e: 74 08 je 0x18
10: 4c 89 ff mov %r15,%rdi
13: e8 da 5b a4 fc call 0xfca45bf2
18: 4d 8b 27 mov (%r15),%r12
1b: 48 89 df mov %rbx,%rdi
1e: 4c 89 f6 mov %r14,%rsi
21: 4c 89 e2 mov %r12,%rdx
24: 8b 5c 24 04 mov 0x4(%rsp),%ebx
28: 89 d9 mov %ebx,%ecx
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 89 d8 mov %ebx,%eax
31: e9 f7 fe ff ff jmp 0xffffff2d
36: 89 d9 mov %ebx,%ecx
38: 80 e1 07 and $0x7,%cl
3b: fe c1 inc %cl
3d: 38 c1 cmp %al,%cl
3f: 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 syzk...@googlegroups.com.

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 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