[PATCH 3.18 018/124] drm/vmwgfx: avoid calling vzalloc with a 0 size in vmw_get_cap_3d_ioctl()

[Greg Kroah-Hartman]

3.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Murray McAllister <murray.mcallis...@insomniasec.com>

commit 63774069d9527a1aeaa4aa20e929ef5e8e9ecc38 upstream.

In vmw_get_cap_3d_ioctl(), a user can supply 0 for a size that is
used in vzalloc(). This eventually calls dump_stack() (in warn_alloc()),
which can leak useful addresses to dmesg.

Add check to avoid a size of 0.

Signed-off-by: Murray McAllister <murray.mcallis...@insomniasec.com>
Reviewed-by: Sinclair Yeh <s...@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c
@@ -161,7 +161,7 @@ int vmw_get_cap_3d_ioctl(struct drm_devi
        bool gb_objects = !!(dev_priv->capabilities & SVGA_CAP_GBOBJECTS);
        struct vmw_fpriv *vmw_fp = vmw_fpriv(file_priv);
 
-       if (unlikely(arg->pad64 != 0)) {
+       if (unlikely(arg->pad64 != 0 || arg->max_size == 0)) {
                DRM_ERROR("Illegal GET_3D_CAP argument.\n");
                return -EINVAL;
        }