Re: [PATCH v3 12/15] kasan: fix bug detection via ksize for HW_TAGS mode

From: Alexander Potapenko <glider@google.com>
To: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Will Deacon <will.deacon@arm.com>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Peter Collingbourne <pcc@google.com>,
	Evgenii Stepanov <eugenis@google.com>,
	Branislav Rankov <Branislav.Rankov@arm.com>,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 12/15] kasan: fix bug detection via ksize for HW_TAGS mode
Date: Fri, 15 Jan 2021 15:04:24 +0100	[thread overview]
Message-ID: <CAG_fn=UqURzPmvP14ULhecDtpgHNOzgcdmm8O8w4iEOWJHu1LQ@mail.gmail.com> (raw)
In-Reply-To: <YAGWA4EWQQd+7e+v@elver.google.com>

On Fri, Jan 15, 2021 at 2:18 PM Marco Elver <elver@google.com> wrote:
>
> On Thu, Jan 14, 2021 at 08:36PM +0100, Andrey Konovalov wrote:
> > The currently existing kasan_check_read/write() annotations are intended
> > to be used for kernel modules that have KASAN compiler instrumentation
> > disabled. Thus, they are only relevant for the software KASAN modes that
> > rely on compiler instrumentation.
> >
> > However there's another use case for these annotations: ksize() checks
> > that the object passed to it is indeed accessible before unpoisoning the
> > whole object. This is currently done via __kasan_check_read(), which is
> > compiled away for the hardware tag-based mode that doesn't rely on
> > compiler instrumentation. This leads to KASAN missing detecting some
> > memory corruptions.
> >
> > Provide another annotation called kasan_check_byte() that is available
> > for all KASAN modes. As the implementation rename and reuse
> > kasan_check_invalid_free(). Use this new annotation in ksize().
> > To avoid having ksize() as the top frame in the reported stack trace
> > pass _RET_IP_ to __kasan_check_byte().
> >
> > Also add a new ksize_uaf() test that checks that a use-after-free is
> > detected via ksize() itself, and via plain accesses that happen later.
> >
> > Link: https://linux-review.googlesource.com/id/Iaabf771881d0f9ce1b969f2a62938e99d3308ec5
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
>
> Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>