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Subject[PATCH v3 2/2] drm/amd: validate user GEM object size
Date
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.

Cc: stable@vger.kernel.org # v4.2+
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 883a4df2386d..a58fb8e021c6 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->pitches[0], 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) {
+ 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);
--
2.20.1.415.g653613c723-goog
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