Re: [PATCH] drm/virtio: fix object leak when drm_gem_handle_create() fails

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:

Pre-existing issues:
- [High] The patch fixes an object leak when drm_gem_handle_create() fails, but misses identical preexisting leaks in virtio_gpu_resource_create_ioctl() and virtio_gpu_resource_create_blob_ioctl().
- [High] Missing cleanup of GEM object internals and fake mmap offset on error paths in virtio_gpu_vram_create().
--

--- Patch [1]: [PATCH] drm/virtio: fix object leak when drm_gem_handle_create() fails ---
commit f5c2e8ad38dcc08de3708efd9e20d6ef52e2a1e8
Author: Junrui Luo <[email protected]>

drm/virtio: fix object leak when drm_gem_handle_create() fails

virtio_gpu_gem_create() owns the reference taken by
virtio_gpu_object_create(). On the drm_gem_handle_create() error path it
calls drm_gem_object_release() instead of dropping that reference.

> diff --git a/drivers/gpu/drm/virtio/virtgpu_gem.c b/drivers/gpu/drm/virtio/virtgpu_gem.c
> index 66c3f6f74e9c6..d2f0b8a3f172b 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_gem.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_gem.c
> @@ -45,7 +45,7 @@ static int virtio_gpu_gem_create(struct drm_file *file,
>  
>  	ret = drm_gem_handle_create(file, &obj->base.base, &handle);
>  	if (ret) {
> -		drm_gem_object_release(&obj->base.base);
> +		drm_gem_object_put(&obj->base.base);
>  		return ret;
>  	}

[Severity: High]
This isn't a bug introduced by this patch, but there are other locations with
this exact same pattern. Does virtio_gpu_resource_create_ioctl() also leak the
object when drm_gem_handle_create() fails?

drivers/gpu/drm/virtio/virtgpu_ioctl.c:virtio_gpu_resource_create_ioctl() {
    ...
    ret = drm_gem_handle_create(file_priv, obj, &handle);
    if (ret) {
        drm_gem_object_release(obj);
        return ret;
    }
    ...
}

Similar leaks appear to be present in virtio_gpu_resource_create_blob_ioctl()
where drm_gem_object_release() is called instead of drm_gem_object_put() on
multiple error paths. Should those be updated to use drm_gem_object_put()
as well to ensure the free hooks are properly executed?

[Severity: High]
This is a pre-existing issue, but might we be missing cleanup of GEM internals
and the mmap offset on error paths in virtio_gpu_vram_create()?

drivers/gpu/drm/virtio/virtgpu_vram.c:virtio_gpu_vram_create() {
    ...
    ret = drm_gem_create_mmap_offset(&vram->base.base.base);
    if (ret) {
        kfree(vram);
        return ret;
    }

    ret = virtio_gpu_resource_id_get(vgdev, &vram->base.hw_res_handle);
    if (ret) {
        kfree(vram);
        return ret;
    }
    ...
}

If virtio_gpu_resource_id_get() fails, drm_gem_create_mmap_offset() has
already added the fake offset to the DRM VMA offset manager's interval tree.
Would calling kfree(vram) here leave a dangling pointer in the interval tree,
potentially causing a use-after-free or tree corruption upon subsequent
accesses?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1