linux-kernel - Re: [PATCH v2] kasan: disable kasan_strings() kunit test when CONFIG_FORTIFY

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Message-ID: <aIyNIdN5dHTgzzQP@e129823.arm.com>
Date: Fri, 1 Aug 2025 10:47:13 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: ryabinin.a.a@...il.com, glider@...gle.com, andreyknvl@...il.com,
	dvyukov@...gle.com, vincenzo.frascino@....com,
	akpm@...ux-foundation.org, kasan-dev@...glegroups.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] kasan: disable kasan_strings() kunit test when
 CONFIG_FORTIFY_SOURCE enabled

Hi,

> On Fri, Aug 01, 2025 at 10:28:05AM +0100, Yeoreum Yun wrote:
> > When CONFIG_FORTIFY_SOURCE is enabled, invalid access from source
> > triggers __fortify_panic() which kills running task.
> >
> > This makes failured of kasan_strings() kunit testcase since the
> > kunit-try-cacth kthread running kasan_string() dies before checking the
> > fault.
>
> "makes failured" sounds wrong. Maybe this?
>
> "This interferes with kasan_strings(), as CONFIG_FORTIFY_SOURCE will trigger
> and kill the test before KASAN can react."
>
> > To address this, add define for __NO_FORTIFY for kasan kunit test.
>
> "To address this" is superfluous. Maybe this?
> "Disable CONFIG_FORTIFY_SOURCE through __NO_FORTIFY for the kasan kunit test to
> remove the interference."

Sorry. I'll refine the commit message with your suggestion.
Thanks

>
> >
> > Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
> > ---
>
> Missing link and changelog to v1.

Right. I'll add

>
> >  mm/kasan/Makefile | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
> > index dd93ae8a6beb..b70d76c167ca 100644
> > --- a/mm/kasan/Makefile
> > +++ b/mm/kasan/Makefile
> > @@ -44,6 +44,10 @@ ifndef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX
> >  CFLAGS_KASAN_TEST += -fno-builtin
> >  endif
> >
> > +ifdef CONFIG_FORTIFY_SOURCE
> > +CFLAGS_KASAN_TEST += -D__NO_FORTIFY
> > +endif
>
> The ifdef is unnecessary. If CONFIG_FORITY_SOURCE is not enabled, the define
> will be a no-op. This also matches other uses of __NO_FORTIFY.

Right. However, it would be good to specify a relationship between
the define and configuration.
So, some usage of __NO_FORTIFY in Makefile using this pattern
(i.e) arch/riscv.

If you don't mind, I remain as it is.

Am I missing something?

Thanks.

[...]
--
Sincerely,
Yeoreum Yun