[PATCH v4 1/2] 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.

Cc: stable at vger.kernel.org # v4.2+
Signed-off-by: Yu Zhao <yuzhao at google.com>
---
 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 686a26de50f9..af0626a2b528 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) {
+		DRM_DEBUG_KMS("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