[PATCH 2/3] drm/amd: validate user pitch alignment

[Yu Zhao]

Userspace may request pitch alignment that is not supported by GPU.
Some requests 32, but GPU ignores it and uses default 64 when cpp is
4. If GEM object is allocated based on the smaller alignment, GPU
DMA will go out of bound.

For GPU that does frame buffer compression, DMA writing out of bound
memory will cause memory corruption.

Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
index e309d26170db..755daa332f8a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
@@ -527,6 +527,15 @@ amdgpu_display_user_framebuffer_create(struct drm_device *dev,
 	struct drm_gem_object *obj;
 	struct amdgpu_framebuffer *amdgpu_fb;
 	int ret;
+	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);
+
+	if (mode_cmd->pitches[0] != pitch) {
+		dev_err(&dev->pdev->dev, "Invalid pitch: expecting %d but got %d\n",
+			pitch, mode_cmd->pitches[0]);
+		return ERR_PTR(-EINVAL);
+	}
 
 	obj = drm_gem_object_lookup(file_priv, mode_cmd->handles[0]);
 	if (obj ==  NULL) {
-- 
2.20.1.415.g653613c723-goog