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Date: Thu, 14 Jul 2016 21:04:18 -0400
From: Rik van Riel <riel@...hat.com>
To: bsingharora@...il.com, Kees Cook <keescook@...omium.org>
Cc: linux-kernel@...r.kernel.org, Casey Schaufler <casey@...aufler-ca.com>,
PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>,
Russell King <linux@...linux.org.uk>,
Catalin Marinas
<catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Ard
Biesheuvel <ard.biesheuvel@...aro.org>,
Benjamin Herrenschmidt
<benh@...nel.crashing.org>,
Michael Ellerman <mpe@...erman.id.au>,
Tony
Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
"David S.
Miller" <davem@...emloft.net>, x86@...nel.org,
Christoph Lameter
<cl@...ux.com>, Pekka Enberg <penberg@...nel.org>,
David Rientjes
<rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Andrew Morton
<akpm@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>, Borislav
Petkov <bp@...e.de>,
Mathias Krause <minipli@...glemail.com>, Jan Kara
<jack@...e.cz>,
Vitaly Wool <vitalywool@...il.com>,
Andrea Arcangeli
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Dmitry Vyukov <dvyukov@...gle.com>,
Laura Abbott
<labbott@...oraproject.org>,
linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
linux-arch@...r.kernel.org, linux-mm@...ck.org,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v2 02/11] mm: Hardened usercopy
On Fri, 2016-07-15 at 09:20 +1000, Balbir Singh wrote:
> > ==
> > + ((unsigned long)end & (unsigned
> > long)PAGE_MASK)))
> > + return NULL;
> > +
> > + /* Allow if start and end are inside the same compound
> > page. */
> > + endpage = virt_to_head_page(end);
> > + if (likely(endpage == page))
> > + return NULL;
> > +
> > + /* Allow special areas, device memory, and sometimes
> > kernel data. */
> > + if (PageReserved(page) && PageReserved(endpage))
> > + return NULL;
>
> If we came here, it's likely that endpage > page, do we need to check
> that only the first and last pages are reserved? What about the ones
> in
> the middle?
I think this will be so rare, we can get away with just
checking the beginning and the end.
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