[RFC][PATCH] Makefile: globally enable VLA warning

[Joe Perches]

On Tue, 2018-06-26 at 10:40 -0700, Kees Cook wrote:
> This is the patch I've got prepared now that fixes for all VLAs have been
> sent to maintainers (some are still under review/adjustment, but there
> aren't any unexplored cases left). My intention would be to have this land
> at the end of the next merge window after all the pending VLA patches
> have landed. I just wanted to get any feedback here, since it touches
> a couple areas in the process and I didn't want anyone to be surprised. :)
[]
> diff --git a/Makefile b/Makefile
[]
> @@ -778,6 +778,9 @@ NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
>  # warn about C99 declaration after statement
>  KBUILD_CFLAGS += $(call cc-option,-Wdeclaration-after-statement,)
>  
> +# VLAs should not be used anywhere in the kernel
> +KBUILD_CFLAGS += $(call cc-option,-Wvla)

I'd probably spell out what a VLA is here.
# VLAs (Variable Length Arrays) should not be used anywhere in the kernel

Beyond that, seems sensible, thanks.