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From:   Andrey Konovalov <andreyknvl@gmail.com>
Date:   Tue, 8 Mar 2022 14:44:52 +0100
Message-ID: <CA+fCnZfeUnCk1zLAjaoWdChyUqaRNLsbdbwJXF-bQEzWSyN6XA@mail.gmail.com>
Subject: Re: [PATCH v2] kasan: fix more unit tests with CONFIG_UBSAN_LOCAL_BOUNDS
 enabled
To:     Peter Collingbourne <pcc@google.com>
Cc:     Marco Elver <elver@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Daniel Micay <danielmicay@gmail.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>, stable@vger.kernel.org,
        Kees Cook <keescook@chromium.org>
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On Thu, Feb 24, 2022 at 1:20 AM Peter Collingbourne <pcc@google.com> wrote:
>
> This is a followup to commit f649dc0e0d7b ("kasan: fix unit tests
> with CONFIG_UBSAN_LOCAL_BOUNDS enabled") that fixes tests that fail
> as a result of __alloc_size annotations being added to the kernel
> allocator functions.
>
> Link: https://linux-review.googlesource.com/id/I4334cafc5db600fda5cebb851b2ee9fd09fb46cc
> Signed-off-by: Peter Collingbourne <pcc@google.com>
> Cc: <stable@vger.kernel.org> # 5.16.x
> Fixes: c37495d6254c ("slab: add __alloc_size attributes for better bounds checking")
> ---
> v2:
> - use OPTIMIZER_HIDE_VAR instead of volatile
>
>  lib/test_kasan.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 26a5c9007653..7c3dfb569445 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -185,6 +185,7 @@ static void kmalloc_pagealloc_oob_right(struct kunit *test)
>         ptr = kmalloc(size, GFP_KERNEL);
>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> +       OPTIMIZER_HIDE_VAR(ptr);
>         KUNIT_EXPECT_KASAN_FAIL(test, ptr[size + OOB_TAG_OFF] = 0);
>
>         kfree(ptr);
> @@ -295,6 +296,7 @@ static void krealloc_more_oob_helper(struct kunit *test,
>                 KUNIT_EXPECT_KASAN_FAIL(test, ptr2[size2] = 'x');
>
>         /* For all modes first aligned offset after size2 must be inaccessible. */
> +       OPTIMIZER_HIDE_VAR(ptr2);
>         KUNIT_EXPECT_KASAN_FAIL(test,
>                 ptr2[round_up(size2, KASAN_GRANULE_SIZE)] = 'x');
>
> @@ -319,6 +321,8 @@ static void krealloc_less_oob_helper(struct kunit *test,
>         /* Must be accessible for all modes. */
>         ptr2[size2 - 1] = 'x';
>
> +       OPTIMIZER_HIDE_VAR(ptr2);
> +
>         /* Generic mode is precise, so unaligned size2 must be inaccessible. */
>         if (IS_ENABLED(CONFIG_KASAN_GENERIC))
>                 KUNIT_EXPECT_KASAN_FAIL(test, ptr2[size2] = 'x');
> --
> 2.35.1.473.g83b2b277ed-goog
>

Acked-by: Andrey Konovalov <andreyknvl@gmail.com>

This patch seems to be in partial conflict with the "kasan: test:
Silence allocation warnings from GCC 12" patch by Kees, which is
already in mm.

Thanks!