From: Andrey Konovalov <andreyknvl@google.com>
To: Marco Elver <elver@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Dmitry Vyukov <dvyukov@google.com>,
Alexander Potapenko <glider@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will.deacon@arm.com>,
Andrey Ryabinin <aryabinin@virtuozzo.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 08/11] kasan: adopt kmalloc_uaf2 test to HW_TAGS mode
Date: Tue, 12 Jan 2021 21:05:18 +0100 [thread overview]
Message-ID: <CAAeHK+w0_WmVZ9kh1QM4vmn3-0oBeWWV3BaLj2+-uh0xj8_BnA@mail.gmail.com> (raw)
In-Reply-To: <X/2md4h0Nki8RNW0@elver.google.com>
On Tue, Jan 12, 2021 at 2:39 PM Marco Elver <elver@google.com> wrote:
>
> On Tue, Jan 05, 2021 at 07:27PM +0100, Andrey Konovalov wrote:
> > In the kmalloc_uaf2() test, the pointers to the two allocated memory
> > blocks might be the same, and the test will fail. With the software
> > tag-based mode, the probability of the that happening is 1/254, so it's
> > hard to observe the failure. For the hardware tag-based mode though,
> > the probablity is 1/14, which is quite noticable.
> >
> > Allow up to 4 attempts at generating different tags for the tag-based
> > modes.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > Link: https://linux-review.googlesource.com/id/Ibfa458ef2804ff465d8eb07434a300bf36388d55
> > ---
> > lib/test_kasan.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> > index b5077a47b95a..b67da7f6e17f 100644
> > --- a/lib/test_kasan.c
> > +++ b/lib/test_kasan.c
> > @@ -375,7 +375,9 @@ static void kmalloc_uaf2(struct kunit *test)
> > {
> > char *ptr1, *ptr2;
> > size_t size = 43;
> > + int counter = 0;
> >
> > +again:
> > ptr1 = kmalloc(size, GFP_KERNEL);
> > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1);
> >
> > @@ -384,6 +386,13 @@ static void kmalloc_uaf2(struct kunit *test)
> > ptr2 = kmalloc(size, GFP_KERNEL);
> > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
> >
> > + /*
> > + * For tag-based KASAN ptr1 and ptr2 tags might happen to be the same.
> > + * Allow up to 4 attempts at generating different tags.
> > + */
> > + if (!IS_ENABLED(CONFIG_KASAN_GENERIC) && ptr1 == ptr2 && counter++ < 4)
> > + goto again;
> > +
>
> Why do we even need a limit? Why not retry until ptr1 != ptr2?
Then the test will hang if it's failing. Let's do up to 16 attempts,
it should be more than enough in practice. Thanks!
next prev parent reply other threads:[~2021-01-12 22:00 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-05 18:27 [PATCH 00/11] kasan: HW_TAGS tests support and fixes Andrey Konovalov
2021-01-05 18:27 ` [PATCH 01/11] kasan: prefix exported functions with kasan_ Andrey Konovalov
2021-01-12 7:38 ` Alexander Potapenko
2021-01-12 11:19 ` Marco Elver
2021-01-05 18:27 ` [PATCH 02/11] kasan: clarify HW_TAGS impact on TBI Andrey Konovalov
2021-01-12 7:40 ` Alexander Potapenko
2021-01-12 11:38 ` Marco Elver
2021-01-05 18:27 ` [PATCH 03/11] kasan: clean up comments in tests Andrey Konovalov
2021-01-12 7:53 ` Alexander Potapenko
2021-01-12 17:55 ` Andrey Konovalov
2021-01-12 13:07 ` Marco Elver
2021-01-05 18:27 ` [PATCH 04/11] kasan: add match-all tag tests Andrey Konovalov
2021-01-12 8:04 ` Alexander Potapenko
2021-01-12 18:10 ` Andrey Konovalov
2021-01-12 13:17 ` Marco Elver
2021-01-12 18:11 ` Andrey Konovalov
2021-01-05 18:27 ` [PATCH 05/11] kasan, arm64: allow using KUnit tests with HW_TAGS mode Andrey Konovalov
2021-01-12 19:01 ` Catalin Marinas
2021-01-15 13:11 ` Andrey Konovalov
2021-01-15 15:04 ` Vincenzo Frascino
2021-01-05 18:27 ` [PATCH 06/11] kasan: rename CONFIG_TEST_KASAN_MODULE Andrey Konovalov
2021-01-12 8:09 ` Alexander Potapenko
2021-01-12 18:26 ` Andrey Konovalov
2021-01-12 13:33 ` Marco Elver
2021-01-12 18:28 ` Andrey Konovalov
2021-01-05 18:27 ` [PATCH 07/11] kasan: add compiler barriers to KUNIT_EXPECT_KASAN_FAIL Andrey Konovalov
2021-01-12 8:18 ` Alexander Potapenko
2021-01-12 19:50 ` Andrey Konovalov
2021-01-12 19:57 ` Andrey Konovalov
2021-01-12 13:34 ` Marco Elver
2021-01-05 18:27 ` [PATCH 08/11] kasan: adopt kmalloc_uaf2 test to HW_TAGS mode Andrey Konovalov
2021-01-12 8:25 ` Alexander Potapenko
2021-01-12 20:04 ` Andrey Konovalov
2021-01-12 13:39 ` Marco Elver
2021-01-12 20:05 ` Andrey Konovalov [this message]
2021-01-05 18:27 ` [PATCH 09/11] kasan: fix memory corruption in kasan_bitops_tags test Andrey Konovalov
2021-01-12 8:30 ` Alexander Potapenko
2021-01-12 20:06 ` Andrey Konovalov
2021-01-13 12:30 ` Alexander Potapenko
2021-01-12 13:55 ` Marco Elver
2021-01-05 18:27 ` [PATCH 10/11] kasan: fix bug detection via ksize for HW_TAGS mode Andrey Konovalov
2021-01-12 14:32 ` Marco Elver
2021-01-12 21:16 ` Andrey Konovalov
2021-01-12 22:54 ` Marco Elver
2021-01-05 18:27 ` [PATCH 11/11] kasan: add proper page allocator tests Andrey Konovalov
2021-01-12 8:57 ` Alexander Potapenko
2021-01-12 14:34 ` Marco Elver
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