[PATCH 3.16 188/212] drm/vmwgfx: NULL pointer dereference in vmw_surface_define_ioctl()

[Ben Hutchings]

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Murray McAllister <murray.mcallister@xxxxxxxxxxxxxxx>

commit 36274ab8c596f1240c606bb514da329add2a1bcd upstream.

Before memory allocations vmw_surface_define_ioctl() checks the
upper-bounds of a user-supplied size, but does not check if the
supplied size is 0.

Add check to avoid NULL pointer dereferences.

Signed-off-by: Murray McAllister <murray.mcallister@xxxxxxxxxxxxxxx>
Reviewed-by: Sinclair Yeh <syeh@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -714,8 +714,8 @@ int vmw_surface_define_ioctl(struct drm_
 	for (i = 0; i < DRM_VMW_MAX_SURFACE_FACES; ++i)
 		num_sizes += req->mip_levels[i];
 
-	if (num_sizes > DRM_VMW_MAX_SURFACE_FACES *
-	    DRM_VMW_MAX_MIP_LEVELS)
+	if (num_sizes > DRM_VMW_MAX_SURFACE_FACES * DRM_VMW_MAX_MIP_LEVELS ||
+	    num_sizes == 0)
 		return -EINVAL;
 
 	size = vmw_user_surface_size + 128 +