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From: Balbir Singh <bsingharora@gmail.com>
To: Rik van Riel <riel@redhat.com>
Cc: bsingharora@gmail.com, Kees Cook <keescook@chromium.org>,
	linux-kernel@vger.kernel.org,
	Casey Schaufler <casey@schaufler-ca.com>,
	PaX Team <pageexec@freemail.hu>,
	Brad Spengler <spender@grsecurity.net>,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Tony Luck <tony.luck@intel.com>,
	Fenghua Yu <fenghua.yu@intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	x86@kernel.org, Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>,
	Mathias Krause <minipli@googlemail.com>, Jan Kara <jack@suse.cz>,
	Vitaly Wool <vitalywool@gmail.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Laura Abbott <labbott@fedoraproject.org>,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-mm@kvack.org,
	kernel-hardening@lists.openwall.com
Subject: Re: [PATCH v2 02/11] mm: Hardened usercopy
Date: Fri, 15 Jul 2016 11:41:51 +1000	[thread overview]
Message-ID: <20160715014151.GA13944@balbir.ozlabs.ibm.com> (raw)
In-Reply-To: <1468544658.30053.26.camel@redhat.com>

On Thu, Jul 14, 2016 at 09:04:18PM -0400, Rik van Riel wrote:
> 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.
>

But do we want to leave a hole where an aware user space
can try a longer copy_* to avoid this check? If it is unlikely
should we just bite the bullet and do the check for the entire
range?

Balbir Singh. 

  reply	other threads:[~2016-07-15  1:42 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-13 21:55 [PATCH v2 0/11] mm: Hardened usercopy Kees Cook
2016-07-13 21:55 ` [PATCH v2 01/11] mm: Implement stack frame object validation Kees Cook
2016-07-13 22:01   ` Andy Lutomirski
2016-07-13 22:04     ` Kees Cook
2016-07-14  5:48       ` Josh Poimboeuf
2016-07-14 18:10         ` Kees Cook
2016-07-14 19:23           ` Josh Poimboeuf
2016-07-14 21:38             ` Kees Cook
2016-07-13 21:55 ` [PATCH v2 02/11] mm: Hardened usercopy Kees Cook
2016-07-14 23:20   ` Balbir Singh
2016-07-15  1:04     ` Rik van Riel
2016-07-15  1:41       ` Balbir Singh [this message]
2016-07-15  4:05         ` Kees Cook
2016-07-15  4:53           ` Kees Cook
2016-07-15 12:55             ` Balbir Singh
2016-07-15  4:25     ` Kees Cook
2016-07-15 19:00       ` [kernel-hardening] " Daniel Micay
2016-07-15 19:14         ` Kees Cook
2016-07-15 19:19           ` Daniel Micay
2016-07-15 19:23             ` Kees Cook
2016-07-13 21:55 ` [PATCH v2 03/11] x86/uaccess: Enable hardened usercopy Kees Cook
2016-07-13 21:55 ` [PATCH v2 04/11] ARM: uaccess: " Kees Cook
2016-07-13 21:55 ` [PATCH v2 05/11] arm64/uaccess: " Kees Cook
2016-07-13 21:55 ` [PATCH v2 06/11] ia64/uaccess: " Kees Cook
2016-07-13 21:56 ` [PATCH v2 07/11] powerpc/uaccess: " Kees Cook
2016-07-13 21:56 ` [PATCH v2 08/11] sparc/uaccess: " Kees Cook
2016-07-13 21:56 ` [PATCH v2 09/11] s390/uaccess: " Kees Cook
2016-07-13 21:56 ` [PATCH v2 10/11] mm: SLAB hardened usercopy support Kees Cook
2016-07-13 21:56 ` [PATCH v2 11/11] mm: SLUB " Kees Cook
2016-07-15  2:05   ` Balbir Singh
2016-07-15  4:29     ` Kees Cook

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