From: Alexander Potapenko <glider@google.com>
To: Marco Elver <elver@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Dmitriy Vyukov <dvyukov@google.com>,
Andrey Konovalov <andreyknvl@google.com>,
Jann Horn <jannh@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
kasan-dev <kasan-dev@googlegroups.com>
Subject: Re: [PATCH mm] kfence: zero guard page after out-of-bounds access
Date: Fri, 12 Mar 2021 14:11:35 +0100 [thread overview]
Message-ID: <CAG_fn=WdpzPxbvzqkpVXjyrUu=GprA2xMBiJdhJqM8cNhABWmw@mail.gmail.com> (raw)
In-Reply-To: <20210312121653.348518-1-elver@google.com>
On Fri, Mar 12, 2021 at 1:16 PM Marco Elver <elver@google.com> wrote:
>
> After an out-of-bounds accesses, zero the guard page before
> re-protecting in kfence_guarded_free(). On one hand this helps make the
> failure mode of subsequent out-of-bounds accesses more deterministic,
> but could also prevent certain information leaks.
>
> Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Alexander Potapenko <glider@google.com>
> ---
> mm/kfence/core.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index 3b8ec938470a..f7106f28443d 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -371,6 +371,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z
>
> /* Restore page protection if there was an OOB access. */
> if (meta->unprotected_page) {
> + memzero_explicit((void *)ALIGN_DOWN(meta->unprotected_page, PAGE_SIZE), PAGE_SIZE);
> kfence_protect(meta->unprotected_page);
> meta->unprotected_page = 0;
> }
> --
> 2.31.0.rc2.261.g7f71774620-goog
>
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
prev parent reply other threads:[~2021-03-12 13:11 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-12 12:16 [PATCH mm] kfence: zero guard page after out-of-bounds access Marco Elver
2021-03-12 13:11 ` Alexander Potapenko [this message]
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