drm/amdgpu: validate user GEM object size

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,
otherwise it could be exploited to reveal sensitive data.

This fix is not done in a common code path because individual
driver might have different requirement.

Cc: stable@vger.kernel.org # v4.2+
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
index cb72d9675ab18600197b32c30a5298f1369307ca..dafc645b2e4ee5e18afe3615d79a691650e57fbd 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
@@ -531,6 +531,7 @@ 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 = mode_cmd->pitches[0] / cpp;
@@ -555,6 +556,13 @@ amdgpu_display_user_framebuffer_create(struct drm_device *dev,
                return ERR_PTR(-EINVAL);
        }
 
+       height = ALIGN(mode_cmd->height, 8);
+       if (obj->size < pitch * height) {
+               DRM_DEBUG_KMS("Invalid GEM size: expecting >= %d but got %zu\n",
+                             pitch * height, obj->size);
+               return ERR_PTR(-EINVAL);
+       }
+
        amdgpu_fb = kzalloc(sizeof(*amdgpu_fb), GFP_KERNEL);
        if (amdgpu_fb == NULL) {
                drm_gem_object_put_unlocked(obj);