Re: [PATCH v2 2/3] arm64: lib: use C string functions with KASAN enabled.

Will Deacon
2018-10-29T11:30:01Z

Hi Andrey, Andrew,

On Mon, Oct 29, 2018 at 11:16:15AM +0000, Andrey Ryabinin wrote:
> On 10/29/2018 01:29 PM, Will Deacon wrote:
> > On Thu, Sep 20, 2018 at 04:56:30PM +0300, Andrey Ryabinin wrote:
> >> ARM64 has asm implementation of memchr(), memcmp(), str[r]chr(),
> >> str[n]cmp(), str[n]len(). KASAN don't see memory accesses in asm
> >> code, thus it can potentially miss many bugs.
> >>
> >> Ifdef out __HAVE_ARCH_* defines of these functions when KASAN is
> >> enabled, so the generic implementations from lib/string.c will be used.
> >>
> >> We can't just remove the asm functions because efistub uses them.
> >> And we can't have two non-weak functions either, so declare the asm
> >> functions as weak.
> >>
> >> Reported-by: Kyeongdon Kim <kyeongdon.kim@lge.com>
> >> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> >> ---
> >> Changes since v1:
> >> - Use WEAK() instead of .weak
> >>
> >> arch/arm64/include/asm/string.h | 14 ++++++++------
> >> arch/arm64/kernel/arm64ksyms.c | 7 +++++--
> >> arch/arm64/lib/memchr.S | 2 +-
> >> arch/arm64/lib/memcmp.S | 2 +-
> >> arch/arm64/lib/strchr.S | 2 +-
> >> arch/arm64/lib/strcmp.S | 2 +-
> >> arch/arm64/lib/strlen.S | 2 +-
> >> arch/arm64/lib/strncmp.S | 2 +-
> >> arch/arm64/lib/strnlen.S | 2 +-
> >> arch/arm64/lib/strrchr.S | 2 +-
> >> 10 files changed, 21 insertions(+), 16 deletions(-)
> >
> > Acked-by: Will Deacon <will.deacon@arm.com>
> >
> > Please post these again after the merge window and we'll figure out how to
> > get them queued.
>
> Andrew sent these patches to Linus couple days ago, so they are in tree
> already.

Oh, good thing I was happy with them in the end, then!

> Something went wrong with mail notification though. I didn't even realize
> that they were in -mm tree, because I didn't receive the usual 'the patch
> has been added to -mm tree' email. But I did receive email that was sent
> to Linus.

Yeah, strange. I usually see the notifications from Andrew.

> Also there was no you or Catalin in Cc tags in 2,3 patches, and in the
> first patch, the Cc tags were corrupted:

:/

Andrew -- have we broken your scripts somehow, or is this just a one-off
for these patches?

Thanks,

Will

> From: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Subject: include/linux/linkage.h: align weak symbols
>
> Since WEAK() supposed to be used instead of ENTRY() to define weak
> symbols, but unlike ENTRY() it doesn't have ALIGN directive. It seems
> there is no actual reason to not have, so let's add ALIGN to WEAK() too.
>
> Link: http://lkml.kernel.org/r/20180920135631.23833-1-aryabinin@virtuozzo.com
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Will Deacon <will.deacon@arm.com>, Catalin Marinas <catalin.marinas@arm.com>
> Cc: Kyeongdon Kim <kyeongdon.kim@lge.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>