Re: [PATCH] drm/virtio: Destroy obj_restore_lock on the final drm_dev_put()

[sashiko-bot@kernel.org]

> virtio_gpu_deinit() calls mutex_destroy() on obj_restore_lock, but
> deinit runs from virtio_gpu_remove() at unbind or PCI remove, and GEM
> objects can outlive that. An open /dev/fb0 keeps the fbdev buffer
> alive, and the fbdev DRM client holds a drm_device reference. When the
> fd is finally closed, the buffer is freed and takes the destroyed lock:
> 
>   fb_release()
>     drm_fbdev_shmem_fb_destroy()
>       drm_client_buffer_delete()
>         virtio_gpu_free_object()
>           virtio_gpu_remove_from_restore_list()
>             mutex_lock(&vgdev->obj_restore_lock)
> 
>   DEBUG_LOCKS_WARN_ON(lock->magic != lock)
>   WARNING: kernel/locking/mutex.c:625 at __mutex_lock+0xf2c/0x12ec
> [ ... ]
> Fixes: 54a970048296 ("drm/virtio: Add support for saving and restoring virtio_gpu_objects")
> Reported-by: syzbot+3590d97d8a586fa955c2@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=3590d97d8a586fa955c2
> Assisted-by: LLM
> Signed-off-by: Abhin Parekadan Jose <abhinjoses@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260929070714.169412-1-abhinjoses@gmail.com?part=1