Shipping MIE (or even MTE) is a many-year effort that requires several parties. I appreciate that Daniel and the GrapheneOS team have been working on making sure the allocator is MTE aware, as well as (I assume) updating Android code to work under MTE. However, to actually ship this, you need someone to design the feature itself, then threat model it, release hardware for it, plumb it through the build system and make sure the OS is aware of it, and then there's a bunch of ongoing work that needs to be done so that it can be released. Much of this work was done by Google and Arm, not Daniel, involving dozens if not hundreds of engineers.

Daniel's position on MTE for a while has been that Google is dragging their feet in turning it on, but he fails to understand that there is more to it than just flipping a switch that he does in his OS. To actually productionize it requires a huge amount of effort that Apple put in here and Daniel, as talented as he is, really can't do. We know this because Google was not able to do it even though they wanted to. (For the avoidance of doubt: Google does want to turn on MTE, they're not just dawdling "just because". The current MTE implementation is not good enough for them.)

It certainly isn't something you can just turn on. I don't know how hardened_malloc works, but one problem is that C malloc() doesn't know the type of memory it's allocating, which is naturally an issue when you need to… allocate typed memory.

You can fix this insofar as you control the compiler and calls to malloc(), which you don't, because third party code may have wrappers around it.