Add alloc_size markers to memory allocation functions

[kees]

In order to improve compile-time object size overflow detection (for things like CONFIG_FORTIFY_SOURCE), add the alloc_size attribute to memory allocation functions. This is complicated by the fact that kmalloc* family may have a usable size greater than the requested size (see ksize()).

For example, see:

anthraxx/linux-hardened@7466f84
anthraxx/linux-hardened@3299e78
anthraxx/linux-hardened@a2aa805
anthraxx/linux-hardened@41d33dc
anthraxx/linux-hardened@a413687

[kees]

Capturing a review note from the recent patch series:

https://lore.kernel.org/lkml/20200120074344.504-1-dja@axtens.net/#r

Kees Cook <keescook@chromium.org> writes:
> On Fri, Feb 07, 2020 at 03:38:22PM -0500, Daniel Micay wrote:
>> There are some uses of ksize in the kernel making use of the real
>> usable size of memory allocations rather than only the requested
>> amount. It's incorrect when mixed with alloc_size markers, since if a
>> number like 14 is passed that's used as the upper bound, rather than a
>> rounded size like 16 returned by ksize. It's unlikely to trigger any
>> issues with only CONFIG_FORTIFY_SOURCE, but it becomes more likely
>> with -fsanitize=object-size or other library-based usage of
>> __builtin_object_size.
>
> I think the solution here is to use a macro that does the per-bucket
> rounding and applies them to the attributes. Keep the bucket size lists
> in sync will likely need some BUILD_BUG_ON()s or similar.

[kees]

Now in linux-next via -mm tree.

https://lore.kernel.org/linux-mm/20210818050841.2226600-1-keescook@chromium.org/

[kees]

Commit c37495d (v5.16)