[PATCH v2 0/6] Provide saturating helpers for allocation

[Kees Cook]

This is a stab at providing three new helpers for allocation size
calculation:

struct_size(), array_size(), and array3_size().

These are implemented on top of Rasmus's overflow checking functions. The
existing allocators are adjusted to use the more efficient overflow
checks as well.

I have left out the 8 tree-wide conversion patches of open-coded
multiplications into the new helpers, as those are largely
unchanged from v1. Everything can be seen here, though:
https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/log/?h=kspp/overflow/array_size

The question remains for what to do with the *calloc() and *_array*()
API. They could be entirely removed in favor of using the new helpers:

kcalloc(n, size, gfp)        ->  kzalloc(array_size(n, size), gfp)
kmalloc_array(n, size, gfp)  ->  kmalloc(array_size(n, size), gfp)

Changes from v1:
- use explicit overflow helpers instead of array_size() helpers.
- drop early-checks for SIZE_MAX.
- protect devm_kmalloc()-family from addition overflow.
- added missing overflow.h includes.
- fixed 0-day issues in a few treewide manual conversions

-Kees