[REGRESSION] BUG: KFENCE: memory corruption in drm_gem_put_pages+0x186/0x250

[Oleksandr Natalenko]

Hello.

I've got a VM from a cloud provider, and since v6.5 I observe the following kfence splat in dmesg during boot:

```
BUG: KFENCE: memory corruption in drm_gem_put_pages+0x186/0x250

Corrupted memory at 0x00000000e173a294 [ ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ] (in kfence-#108):
 drm_gem_put_pages+0x186/0x250
 drm_gem_shmem_put_pages_locked+0x43/0xc0
 drm_gem_shmem_object_vunmap+0x83/0xe0
 drm_gem_vunmap_unlocked+0x46/0xb0
 drm_fbdev_generic_helper_fb_dirty+0x1dc/0x310
 drm_fb_helper_damage_work+0x96/0x170
 process_one_work+0x254/0x470
 worker_thread+0x55/0x4f0
 kthread+0xe8/0x120
 ret_from_fork+0x34/0x50
 ret_from_fork_asm+0x1b/0x30

kfence-#108: 0x00000000cda343af-0x00000000aec2c095, size=3072, cache=kmalloc-4k

allocated by task 51 on cpu 0 at 14.668667s:
 drm_gem_get_pages+0x94/0x2b0
 drm_gem_shmem_get_pages+0x5d/0x110
 drm_gem_shmem_object_vmap+0xc4/0x1e0
 drm_gem_vmap_unlocked+0x3c/0x70
 drm_client_buffer_vmap+0x23/0x50
 drm_fbdev_generic_helper_fb_dirty+0xae/0x310
 drm_fb_helper_damage_work+0x96/0x170
 process_one_work+0x254/0x470
 worker_thread+0x55/0x4f0
 kthread+0xe8/0x120
 ret_from_fork+0x34/0x50
 ret_from_fork_asm+0x1b/0x30

freed by task 51 on cpu 0 at 14.668697s:
 drm_gem_put_pages+0x186/0x250
 drm_gem_shmem_put_pages_locked+0x43/0xc0
 drm_gem_shmem_object_vunmap+0x83/0xe0
 drm_gem_vunmap_unlocked+0x46/0xb0
 drm_fbdev_generic_helper_fb_dirty+0x1dc/0x310
 drm_fb_helper_damage_work+0x96/0x170
 process_one_work+0x254/0x470
 worker_thread+0x55/0x4f0
 kthread+0xe8/0x120
 ret_from_fork+0x34/0x50
 ret_from_fork_asm+0x1b/0x30

CPU: 0 PID: 51 Comm: kworker/0:2 Not tainted 6.5.0-pf4 #1 8b557a4173114d86eef7240f7a080080cfc4617e
Hardware name: Red Hat KVM, BIOS 1.11.0-2.el7 04/01/2014
Workqueue: events drm_fb_helper_damage_work
```

This repeats a couple of times and then stops.

Currently, I'm running v6.5.5. So far, there's no impact on how VM functions for me.

The VGA adapter is as follows: 00:02.0 VGA compatible controller: Cirrus Logic GD 5446

Please check.

Thanks.

-- 
Oleksandr Natalenko (post-factum)
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