Re: [PATCH -fixes] vmwgfx: fix incorrect VRAM size check in vmw_kms_fb_create()

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This looks good, although I want to do a quick test to verify that it doesn't break anything.

I'll get back as soon as possible.

/Thomas

On 12/21/2011 11:18 AM, Xi Wang wrote:
Commit e133e737 didn't correctly fix the integer overflow issue.

-	unsigned int required_size;
+	u64 required_size;
	...
	required_size = mode_cmd->pitch * mode_cmd->height;
-	if (unlikely(required_size>  dev_priv->vram_size)) {
+	if (unlikely(required_size>  (u64) dev_priv->vram_size)) {

Note that both pitch and height are u32.  Their product is still u32 and
would overflow before being assigned to required_size.  A correct way is
to convert pitch and height to u64 before the multiplication.

	required_size = (u64)mode_cmd->pitch * (u64)mode_cmd->height;

This patch calls the existing vmw_kms_validate_mode_vram() for
validation.

Signed-off-by: Xi Wang<xi.wang@xxxxxxxxx>
---
  drivers/gpu/drm/vmwgfx/vmwgfx_kms.c |    6 +++---
  1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index 8aa1dbb..f94b33a 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -1093,7 +1093,6 @@ static struct drm_framebuffer *vmw_kms_fb_create(struct drm_device *dev,
  	struct vmw_surface *surface = NULL;
  	struct vmw_dma_buffer *bo = NULL;
  	struct ttm_base_object *user_obj;
-	u64 required_size;
  	int ret;

  	/**
@@ -1102,8 +1101,9 @@ static struct drm_framebuffer *vmw_kms_fb_create(struct drm_device *dev,
  	 * requested framebuffer.
  	 */

-	required_size = mode_cmd->pitch * mode_cmd->height;
-	if (unlikely(required_size>  (u64) dev_priv->vram_size)) {
+	if (!vmw_kms_validate_mode_vram(dev_priv,
+					mode_cmd->pitch,
+					mode_cmd->height)) {
  		DRM_ERROR("VRAM size is too small for requested mode.\n");
  		return ERR_PTR(-ENOMEM);
  	}

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