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From:   Alexander Potapenko <glider@google.com>
Date:   Tue, 12 Jan 2021 09:25:53 +0100
Message-ID: <CAG_fn=X0YY8+FUWWyLqGUu5Z6-eEaSAOVGYj9PKzhzqyA1BvsA@mail.gmail.com>
Subject: Re: [PATCH 08/11] kasan: adopt kmalloc_uaf2 test to HW_TAGS mode
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Marco Elver <elver@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>
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Nit: s/adopt/adapt in the title.


> +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;
> +

Looks like we are leaking memory allocated for ptr2 here?