[PATCH v2] drm/exynos: check if framebuffer and gem size are valid or not.

[Inki Dae]

with addfb request by user, wrong framebuffer or gem size could be sent
to kernel side so this could induce invalid memory access by dma of a device.
this patch checks if framebuffer and gem size are valid or not to avoid
this issue.

Changelog v2:
use fb->pitches instead of caculating it with fb->width and fb->bpp
as line size.

Signed-off-by: Inki Dae <inki.dae at samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
---
 drivers/gpu/drm/exynos/exynos_drm_fb.c |   47 ++++++++++++++++++++++++++++++-
 1 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_fb.c b/drivers/gpu/drm/exynos/exynos_drm_fb.c
index 4ccfe43..f1b1008 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_fb.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fb.c
@@ -48,6 +48,44 @@ struct exynos_drm_fb {
 	struct exynos_drm_gem_obj	*exynos_gem_obj[MAX_FB_BUFFER];
 };
 
+static int check_fb_gem_size(struct drm_device *drm_dev,
+				struct drm_framebuffer *fb,
+				unsigned int nr)
+{
+	unsigned long fb_size;
+	struct drm_gem_object *obj;
+	struct exynos_drm_gem_obj *exynos_gem_obj;
+	struct exynos_drm_fb *exynos_fb = to_exynos_fb(fb);
+
+	/* in case of RGB format, only one plane is used. */
+	if (nr < 2) {
+		exynos_gem_obj = exynos_fb->exynos_gem_obj[0];
+		obj = &exynos_gem_obj->base;
+		fb_size = fb->pitches[0] * fb->height;
+
+		if (fb_size != exynos_gem_obj->packed_size) {
+			DRM_ERROR("invalid fb or gem size.\n");
+			return -EINVAL;
+		}
+	/* in case of NV12MT, YUV420M and so on, two and three planes. */
+	} else {
+		unsigned int i;
+
+		for (i = 0; i < nr; i++) {
+			exynos_gem_obj = exynos_fb->exynos_gem_obj[i];
+			obj = &exynos_gem_obj->base;
+			fb_size = fb->pitches[i] * fb->height;
+
+			if (fb_size != exynos_gem_obj->packed_size) {
+				DRM_ERROR("invalid fb or gem size.\n");
+				return -EINVAL;
+			}
+		}
+	}
+
+	return 0;
+}
+
 static void exynos_drm_fb_destroy(struct drm_framebuffer *fb)
 {
 	struct exynos_drm_fb *exynos_fb = to_exynos_fb(fb);
@@ -134,8 +172,7 @@ exynos_user_fb_create(struct drm_device *dev, struct drm_file *file_priv,
 	struct drm_gem_object *obj;
 	struct drm_framebuffer *fb;
 	struct exynos_drm_fb *exynos_fb;
-	int nr;
-	int i;
+	int nr, i, ret;
 
 	DRM_DEBUG_KMS("%s\n", __FILE__);
 
@@ -166,6 +203,12 @@ exynos_user_fb_create(struct drm_device *dev, struct drm_file *file_priv,
 		exynos_fb->exynos_gem_obj[i] = to_exynos_gem_obj(obj);
 	}
 
+	ret = check_fb_gem_size(dev, fb, nr);
+	if (ret < 0) {
+		exynos_drm_fb_destroy(fb);
+		return ERR_PTR(ret);
+	}
+
 	return fb;
 }
 
-- 
1.7.4.1