GMS-2023-171: Security bug in ConvertToSinglePlane when used with untrusted content from the DDS loader

Impact

A memory overwrite bug was reported by a security researcher in the ConvertToSinglePlane method via the texconv command-line tool when given an invalid height for planar video textures such as NV12. This can be a potential security bug for any clients of the library who follow the same pattern.

This issue does not impact use of the DDS texture loader itself, only when combined with ConvertToSinglePlane for converting multi-planar video formats. All other functions in the library fail immediately if given images in planar formats.

Patches

The fix to the specific area as well as general hardening can be found in this PR and will be included in the January 2023 or later release of DirectXTex.

Workarounds

If your code makes use of ConvertToSinglePlane, you can validate that the width & height alignment requirements are met for the input image before calling the function.