[syzbot] [dri?] WARNING in drm_fbdev_shmem_helper_fb_dirty

[syzbot <syzbot+369ee6a6e9d0bbf14b37@syzkaller.appspotmail.com>]

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+369ee6a6e9d0bbf14b37@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


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