[stefanatwork]

The bufferType and bufferSlot members of RTCInterpolateArguments and RTCInterpolateNArguments are passed from the public API straight into the per geometry interpolate_impl() routines, where the slot is used to index the fixed size vertices, tangents and vertexAttribs arrays of buffer descriptors. The only guard was an assert that is removed in release builds, and that was additionally off by one for vertex attributes as it used bufferSlot <= vertexAttribs.size() instead of <.

An out of range slot therefore read a buffer descriptor past the end of the descriptor array. The resulting pointer and stride were then used to load vertex data, and the loaded bytes were written into the caller visible interpolation output arrays.

This affects all interpolatable geometry types, both the vertex and the vertex attribute buffer branch, and both rtcInterpolate and rtcInterpolateN. A buffer type other than RTC_BUFFER_TYPE_VERTEX or RTC_BUFFER_TYPE_VERTEX_ATTRIBUTE was silently treated as a vertex buffer instead of being rejected.

Add Geometry::checkInterpolateBuffer(), which rejects unsupported buffer types, vertex slots that are not smaller than numTimeSteps, and vertex attribute slots that are not smaller than the vertex attribute count. These bounds also cover the vertex_buffer_tags and vertex_attrib_buffer_tags arrays of subdivision meshes, which are sized by the same two counts. Invalid requests now raise RTC_ERROR_INVALID_ARGUMENT and interpolate no data. Use the helper at all interpolation sites, replacing the asserts, and document the requirement.

[svenwoop]

This function will be used during rendering, do we really want to put runtime checks here? IMHO the asserts are fine and API documentation should specify what input to expect.

If we add checks then usage of checkInterpolateBuffer is not optimal as this adds additional branching on bufferType that the code anyway does already. There were some asserts inside the if (bufferType == RTC_BUFFER_TYPE_VERTEX_ATTRIBUTE) conditional that can get converted to exception.