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Date: Mon, 12 Feb 2024 09:37:10 +0100
From: Paul =?utf-8?Q?Heidekr=C3=BCger?= <paul.heidekrueger@tum.de>
To: Andrey Konovalov <andreyknvl@gmail.com>
Cc: akpm@linux-foundation.org, dvyukov@google.com, elver@google.com, 
	glider@google.com, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, 
	linux-mm@kvack.org, ryabinin.a.a@gmail.com, vincenzo.frascino@arm.com, 
	Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH v2] kasan: add atomic tests
Message-ID: <mofzkwb2a2wr5z7kg2fe3lowzdca7kqvol5hevhj5dcs5pxvu2@7d4gydk3enon>
References: <20240202113259.3045705-1-paul.heidekrueger@tum.de>
 <20240211091720.145235-1-paul.heidekrueger@tum.de>
 <CA+fCnZcfUyqzok0yV2uvsDdhiT95Y-KYnozY77y04YDBwKhj-Q@mail.gmail.com>
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On 12.02.2024 00:16, Andrey Konovalov wrote:
> On Sun, Feb 11, 2024 at 10:17 AM Paul Heidekrüger
> <paul.heidekrueger@tum.de> wrote:
> >
> > Test that KASan can detect some unsafe atomic accesses.
> >
> > As discussed in the linked thread below, these tests attempt to cover
> > the most common uses of atomics and, therefore, aren't exhaustive.
> >
> > CC: Marco Elver <elver@google.com>
> > CC: Andrey Konovalov <andreyknvl@gmail.com>
> > Link: https://lore.kernel.org/all/20240131210041.686657-1-paul.heidekrueger@tum.de/T/#u
> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=214055
> > Reviewed-by: Marco Elver <elver@google.com>
> > Tested-by: Marco Elver <elver@google.com>
> > Acked-by: Mark Rutland <mark.rutland@arm.com>
> > Signed-off-by: Paul Heidekrüger <paul.heidekrueger@tum.de>
> > ---
> > Changes PATCH v1 -> PATCH v2:
> > * Make explicit cast implicit as per Mark's feedback
> > * Increase the size of the "a2" allocation as per Andrey's feedback
> > * Add tags
> >
> > Changes PATCH RFC v2 -> PATCH v1:
> > * Remove casts to void*
> > * Remove i_safe variable
> > * Add atomic_long_* test cases
> > * Carry over comment from kasan_bitops_tags()
> >
> > Changes PATCH RFC v1 -> PATCH RFC v2:
> > * Adjust size of allocations to make kasan_atomics() work with all KASan modes
> > * Remove comments and move tests closer to the bitops tests
> > * For functions taking two addresses as an input, test each address in a separate function call.
> > * Rename variables for clarity
> > * Add tests for READ_ONCE(), WRITE_ONCE(), smp_load_acquire() and smp_store_release()
> >
> >  mm/kasan/kasan_test.c | 79 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 79 insertions(+)
> >
> > diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
> > index 8281eb42464b..7bf09699b145 100644
> > --- a/mm/kasan/kasan_test.c
> > +++ b/mm/kasan/kasan_test.c
> > @@ -1150,6 +1150,84 @@ static void kasan_bitops_tags(struct kunit *test)
> >         kfree(bits);
> >  }
> >
> > +static void kasan_atomics_helper(struct kunit *test, void *unsafe, void *safe)
> > +{
> > +       int *i_unsafe = unsafe;
> > +
> > +       KUNIT_EXPECT_KASAN_FAIL(test, READ_ONCE(*i_unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, WRITE_ONCE(*i_unsafe, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, smp_load_acquire(i_unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, smp_store_release(i_unsafe, 42));
> > +
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_read(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_set(unsafe, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_add(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_sub(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_inc(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_dec(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_and(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_andnot(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_or(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_xor(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_xchg(unsafe, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_cmpxchg(unsafe, 21, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_try_cmpxchg(unsafe, safe, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_try_cmpxchg(safe, unsafe, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_sub_and_test(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_dec_and_test(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_inc_and_test(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_add_negative(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_add_unless(unsafe, 21, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_inc_not_zero(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_inc_unless_negative(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_dec_unless_positive(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_dec_if_positive(unsafe));
> > +
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_read(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_set(unsafe, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_add(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_sub(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_inc(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_dec(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_and(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_andnot(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_or(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_xor(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_xchg(unsafe, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_cmpxchg(unsafe, 21, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_try_cmpxchg(unsafe, safe, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_try_cmpxchg(safe, unsafe, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_sub_and_test(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_dec_and_test(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_inc_and_test(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_add_negative(42, unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_add_unless(unsafe, 21, 42));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_inc_not_zero(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_inc_unless_negative(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_dec_unless_positive(unsafe));
> > +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_dec_if_positive(unsafe));
> > +}
> > +
> > +static void kasan_atomics(struct kunit *test)
> > +{
> > +       void *a1, *a2;
> > +
> > +       /*
> > +        * Just as with kasan_bitops_tags(), we allocate 48 bytes of memory such
> > +        * that the following 16 bytes will make up the redzone.
> > +        */
> > +       a1 = kzalloc(48, GFP_KERNEL);
> > +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, a1);
> > +       a2 = kzalloc(sizeof(atomic_long_t), GFP_KERNEL);
> > +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, a1);
> 
> This should check for a2, not a1. Sorry for not spotting this before.

No need to apologise. I'm the one who made the mistake, so I'm the one who 
should've spotted it in the first place :-)

> > +
> > +       /* Use atomics to access the redzone. */
> > +       kasan_atomics_helper(test, a1 + 48, a2);
> > +
> > +       kfree(a1);
> > +       kfree(a2);
> > +}
> > +
> >  static void kmalloc_double_kzfree(struct kunit *test)
> >  {
> >         char *ptr;
> > @@ -1553,6 +1631,7 @@ static struct kunit_case kasan_kunit_test_cases[] = {
> >         KUNIT_CASE(kasan_strings),
> >         KUNIT_CASE(kasan_bitops_generic),
> >         KUNIT_CASE(kasan_bitops_tags),
> > +       KUNIT_CASE(kasan_atomics),
> >         KUNIT_CASE(kmalloc_double_kzfree),
> >         KUNIT_CASE(rcu_uaf),
> >         KUNIT_CASE(workqueue_uaf),
> > --
> > 2.40.1
> >
> 
> With the mentioned change:
> 
> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
> 
> Thank you!

Just sent v3.

Many thanks,
Paul