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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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