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. After I started >> writing tests (now in lkdtm in -next) for Casey's earlier port, 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
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