[PATCH] malloc/malloc.c: Mitigate null-byte overflow attacks

[DJ Delorie]

Sorry, I'm not getting my idea across.  Let me try again.

I'm thinking, something that tests a size *before* we consider it in the
context of a chunk, such as this one:

  https://www.sourceware.org/ml/libc-alpha/2017-10/msg01202.html

One might also consider certain combinations of the three low order
bits, like setting both the A (arena) and M (mmap'd) bits at the same
time.

Even if we had such a test, though, we'd still need to carefully
consider all the places we'd use it - comparing possible utility vs
performance degredation.

But please don't consider this a requirement for any pending patches, I
was just thinking out loud ;-)