linux-kernel - [PATCH v5 2/2] drm/amd: validate user GEM object size

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Message-Id: <20181230010021.196990-2-yuzhao@google.com>
Date:   Sat, 29 Dec 2018 18:00:21 -0700
From:   Yu Zhao <yuzhao@...gle.com>
To:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Christian König <christian.koenig@....com>,
        Alex Deucher <alexander.deucher@....com>
Cc:     David Zhou <David1.Zhou@....com>, Samuel Li <Samuel.Li@....com>,
        Harry Wentland <harry.wentland@....com>,
        Junwei Zhang <Jerry.Zhang@....com>,
        Daniel Stone <daniels@...labora.com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Yu Zhao <yuzhao@...gle.com>,
        stable@...r.kernel.org
Subject: [PATCH v5 2/2] drm/amd: 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@...r.kernel.org # v4.2+
Signed-off-by: Yu Zhao <yuzhao@...gle.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 16af80ccd0a0..61c075a78ee1 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 = mode_cmd->pitches[0] / cpp;
@@ -557,6 +558,13 @@ 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