From: Kees Cook <keescook@chromium.org>
To: Balbir Singh <bsingharora@gmail.com>
Cc: Rik van Riel <riel@redhat.com>,
LKML <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" <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>,
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"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
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"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
sparclinux <sparclinux@vger.kernel.org>,
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Linux-MM <linux-mm@kvack.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH v2 02/11] mm: Hardened usercopy
Date: Thu, 14 Jul 2016 21:53:31 -0700 [thread overview]
Message-ID: <CAGXu5jLuQPdBH4a0BF9AgH7qQubfoz+fFW2sTi2rRxsU8u_8QQ@mail.gmail.com> (raw)
In-Reply-To: <CAGXu5jJy4O4tV2sB=MSkYh2DEfxUYkH4Q3ghmrHEGc6s-k285A@mail.gmail.com>
On Thu, Jul 14, 2016 at 9:05 PM, Kees Cook <keescook@chromium.org> wrote:
> On Thu, Jul 14, 2016 at 6:41 PM, Balbir Singh <bsingharora@gmail.com> wrote:
>> 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?
>
> I'd be okay with expanding the test -- it should be an extremely rare
> situation already since the common Reserved areas (kernel data) will
> have already been explicitly tested.
>
> What's the best way to do "next page"? Should it just be:
>
> for ( ; page <= endpage ; ptr += PAGE_SIZE, page = virt_to_head_page(ptr) ) {
> if (!PageReserved(page))
> return "<spans multiple pages>";
> }
>
> return NULL;
>
> ?
Er, I was testing the wrong thing. How about:
/*
* Reject if range is not Reserved (i.e. special or device memory),
* since then the object spans several independently allocated pages.
*/
for (; ptr <= end ; ptr += PAGE_SIZE, page = virt_to_head_page(ptr)) {
if (!PageReserved(page))
return "<spans multiple pages>";
}
return NULL;
--
Kees Cook
Chrome OS & Brillo Security
next prev parent reply other threads:[~2016-07-15 4:53 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
2016-07-15 4:05 ` Kees Cook
2016-07-15 4:53 ` Kees Cook [this message]
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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