linux-kernel - Re: [PATCH 8/8] kasan: test: avoid corrupting memory in kasan_rcu

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Date:   Thu, 12 Aug 2021 10:50:30 +0200
From:   Marco Elver <elver@...gle.com>
To:     andrey.konovalov@...ux.dev
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/8] kasan: test: avoid corrupting memory in kasan_rcu_uaf

On Wed, 11 Aug 2021 at 21:34, <andrey.konovalov@...ux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@...il.com>
>
> kasan_rcu_uaf() writes to freed memory via kasan_rcu_reclaim(), which is
> only safe with the GENERIC mode (as it uses quarantine). For other modes,
> this test corrupts kernel memory, which might result in a crash.
>
> Turn the write into a read.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...il.com>

Reviewed-by: Marco Elver <elver@...gle.com>


> ---
>  lib/test_kasan_module.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/test_kasan_module.c b/lib/test_kasan_module.c
> index fa73b9df0be4..7ebf433edef3 100644
> --- a/lib/test_kasan_module.c
> +++ b/lib/test_kasan_module.c
> @@ -71,7 +71,7 @@ static noinline void __init kasan_rcu_reclaim(struct rcu_head *rp)
>                                                 struct kasan_rcu_info, rcu);
>
>         kfree(fp);
> -       fp->i = 1;
> +       ((volatile struct kasan_rcu_info *)fp)->i;
>  }
>
>  static noinline void __init kasan_rcu_uaf(void)
> --
> 2.25.1
>