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SubjectRe: [PATCH 3/3] drm/amd: validate user GEM object size
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On 2018-12-21 4:10 a.m., Yu Zhao wrote:
> When creating frame buffer, userspace may request to attach to a
> previously allocated GEM object that is smaller than what GPU
> requires. Validation must be done to prevent out-of-bound DMA,
> which could not only corrupt memory but also reveal sensitive data.
>
> This fix is not done in a common code path because individual
> driver might have different requirement.
>
> Signed-off-by: Yu Zhao <yuzhao@google.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> index 755daa332f8a..bb48b016cc68 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> @@ -527,6 +527,7 @@ amdgpu_display_user_framebuffer_create(struct drm_device *dev,
> struct drm_gem_object *obj;
> struct amdgpu_framebuffer *amdgpu_fb;
> int ret;
> + int height;
> struct amdgpu_device *adev = dev->dev_private;
> int cpp = drm_format_plane_cpp(mode_cmd->pixel_format, 0);
> int pitch = amdgpu_align_pitch(adev, mode_cmd->width, cpp, false);
> @@ -550,6 +551,13 @@ amdgpu_display_user_framebuffer_create(struct drm_device *dev,
> return ERR_PTR(-EINVAL);
> }
>
> + height = ALIGN(mode_cmd->height, 8);
> + if (obj->size < pitch * height) {
> + dev_err(&dev->pdev->dev, "Invalid GEM size: expecting %d but got %d\n",
> + pitch * height, obj->size);

Same comment as patch 2, and maybe write "expecting >= %d but got %d"
for clarity.


--
Earthling Michel Dänzer | http://www.amd.com
Libre software enthusiast | Mesa and X developer

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