[PATCH 06/14] Fix CFLAGS for UBSAN_BOUNDS on Clang

[Kees Cook]

On Mon, Sep 14, 2020 at 05:27:42PM +0000, George-Aurelian Popescu wrote:
> From: George Popescu <georgepope at google.com>
> 
> When the kernel is compiled with Clang, UBSAN_BOUNDS inserts a brk after
> the handler call, preventing it from printing any information processed
> inside the buffer.
> For Clang -fsanitize=bounds expands to -fsanitize=array-bounds and
> -fsanitize=local-bounds, and the latter adds a brk after the handler
> call

That sounds like a compiler bug?

> Signed-off-by: George Popescu <georgepope at google.com>
> ---
>  scripts/Makefile.ubsan | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
> index 27348029b2b8..3d15ac346c97 100644
> --- a/scripts/Makefile.ubsan
> +++ b/scripts/Makefile.ubsan
> @@ -4,7 +4,14 @@ ifdef CONFIG_UBSAN_ALIGNMENT
>  endif
>  
>  ifdef CONFIG_UBSAN_BOUNDS
> -      CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
> +      # For Clang -fsanitize=bounds translates to -fsanitize=array-bounds and
> +      # -fsanitize=local-bounds; the latter adds a brk right after the
> +      # handler is called.
> +      ifdef CONFIG_CC_IS_CLANG
> +            CFLAGS_UBSAN += $(call cc-option, -fsanitize=array-bounds)

This would mean losing the local-bounds coverage? Isn't that for locally
defined arrays on the stack?

> +      else
> +            CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
> +      endif
>  endif
>  
>  ifdef CONFIG_UBSAN_MISC
> -- 
> 2.28.0.618.gf4bc123cb7-goog
> 

-- 
Kees Cook