memory tagging should be a game changer for C and C++; get with the program, @intel and @apple!!pic.twitter.com/z2vXAtTb7z
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Then UAF becomes exploitable again. This shows the weakness of 4-bit tag: doesn’t take many allocations to get a collision.
How about rv128 with 80 bit tags? 
See above about UAF protection being best-effort/statistical. *Fundamentally*, best you can do against UAF without an identifier space large enough to never reuse identifiers is no better than MTE, except ability to enlarge tag.
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