[PATCHv3] malloc: Make sure tcache_key is odd enough

[Wilco Dijkstra]

Hi Cupertino,

> In order to avoid having tcache_key repeated through memory, why don't
> we mangle it as well with, maybe not exactly as in PROTECT_PTR, however
> using the location of chunk. A XOR perhaps ?
> 
> I don't think it would have such a huge performance impact on the
> overhaul execution time.

What problem would that solve? The detection of double-free in tcache is
already quite limited. Using many different "keys" would only increase
collisions with user data (which is what we are trying to avoid with this patch).

Cheers,
Wilco