[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 7 Jul 2016 13:27:03 -0400
From: Kees Cook <keescook@...omium.org>
To: Christian Borntraeger <borntraeger@...ibm.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Rik van Riel <riel@...hat.com>,
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" <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>, Mathias Krause <minipli@...glemail.com>, Jan Kara <jack@...e.cz>,
Vitaly Wool <vitalywool@...il.com>, Andrea Arcangeli <aarcange@...hat.com>,
Dmitry Vyukov <dvyukov@...gle.com>, Laura Abbott <labbott@...oraproject.org>,
"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, linux-ia64@...r.kernel.org,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>, sparclinux <sparclinux@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 0/9] mm: Hardened usercopy
On Thu, Jul 7, 2016 at 3:30 AM, Christian Borntraeger
<borntraeger@...ibm.com> wrote:
> On 07/07/2016 12:25 AM, Kees Cook wrote:
>> Hi,
>>
>> This is a start of the mainline port of PAX_USERCOPY[1]. After I started
>> writing tests (now in lkdtm in -next) for Casey's earlier port[2], I
>> kept tweaking things further and further until I ended up with a whole
>> new patch series. To that end, I took Rik's feedback and made a number
>> of other changes and clean-ups as well.
>>
>> Based on my understanding, PAX_USERCOPY was designed to catch a few
>> classes of flaws around the use of copy_to_user()/copy_from_user(). These
>> changes don't touch get_user() and put_user(), since these operate on
>> constant sized lengths, and tend to be much less vulnerable. There
>> are effectively three distinct protections in the whole series,
>> each of which I've given a separate CONFIG, though this patch set is
>> only the first of the three intended protections. (Generally speaking,
>> PAX_USERCOPY covers what I'm calling CONFIG_HARDENED_USERCOPY (this) and
>> CONFIG_HARDENED_USERCOPY_WHITELIST (future), and PAX_USERCOPY_SLABS covers
>> CONFIG_HARDENED_USERCOPY_SPLIT_KMALLOC (future).)
>>
>> This series, which adds CONFIG_HARDENED_USERCOPY, checks that objects
>> being copied to/from userspace meet certain criteria:
>> - if address is a heap object, the size must not exceed the object's
>> allocated size. (This will catch all kinds of heap overflow flaws.)
>> - if address range is in the current process stack, it must be within the
>> current stack frame (if such checking is possible) or at least entirely
>> within the current process's stack. (This could catch large lengths that
>> would have extended beyond the current process stack, or overflows if
>> their length extends back into the original stack.)
>> - if the address range is part of kernel data, rodata, or bss, allow it.
>> - if address range is page-allocated, that it doesn't span multiple
>> allocations.
>> - if address is within the kernel text, reject it.
>> - everything else is accepted
>>
>> The patches in the series are:
>> - The core copy_to/from_user() checks, without the slab object checks:
>> 1- mm: Hardened usercopy
>> - Per-arch enablement of the protection:
>> 2- x86/uaccess: Enable hardened usercopy
>> 3- ARM: uaccess: Enable hardened usercopy
>> 4- arm64/uaccess: Enable hardened usercopy
>> 5- ia64/uaccess: Enable hardened usercopy
>> 6- powerpc/uaccess: Enable hardened usercopy
>> 7- sparc/uaccess: Enable hardened usercopy
>
> Was there a reason why you did not change s390?
No reason -- just didn't have a good build setup for testing it.
(Everything but arm64 was already in grsecurity, and I was able to
build-test arm64 when I added it there.) I would love to include s390
too!
-Kees
--
Kees Cook
Chrome OS & Brillo Security
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
