linux-kernel - Re: [PATCH 08/11] kasan: adopt kmalloc_uaf2 test to HW

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Date:   Tue, 12 Jan 2021 21:04:34 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will.deacon@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/11] kasan: adopt kmalloc_uaf2 test to HW_TAGS mode

On Tue, Jan 12, 2021 at 9:26 AM Alexander Potapenko <glider@...gle.com> wrote:
>
> 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?

Will fix in v2, thanks!