[kanox]

Shouldn't proper IOMMU usage prevent this?

In theory when properly configured the DSP or GPU should be unable to touch system RAM outside of buffers that are specifically assigned to them.

I'm not very familiar with the status of IOMMU on Android devices.

[monocasa]

It's dependent on the SoC whether there's IOMMUs at all and whether they're rigged up to all the bus masters in the system. A lot don't have them as it was seen as a virtualization feature rather than a security feature for the longest time.