From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id D7AB16B025F for ; Mon, 18 Jul 2016 04:26:23 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id y134so306731230pfg.1 for ; Mon, 18 Jul 2016 01:26:23 -0700 (PDT) Received: from mail-pa0-x241.google.com (mail-pa0-x241.google.com. [2607:f8b0:400e:c03::241]) by mx.google.com with ESMTPS id w62si2282357pfw.199.2016.07.18.01.26.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 Jul 2016 01:26:23 -0700 (PDT) Received: by mail-pa0-x241.google.com with SMTP id dx3so10693421pab.2 for ; Mon, 18 Jul 2016 01:26:22 -0700 (PDT) Message-ID: <1468830403.2800.0.camel@gmail.com> Subject: Re: [PATCH v3 00/11] mm: Hardened usercopy From: Balbir Singh Date: Mon, 18 Jul 2016 18:26:43 +1000 In-Reply-To: <1468619065-3222-1-git-send-email-keescook@chromium.org> References: <1468619065-3222-1-git-send-email-keescook@chromium.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Kees Cook , linux-kernel@vger.kernel.org Cc: Daniel Micay , Josh Poimboeuf , Rik van Riel , Casey Schaufler , PaX Team , Brad Spengler , Russell King , Catalin Marinas , Will Deacon , Ard Biesheuvel , Benjamin Herrenschmidt , Michael Ellerman , Tony Luck , Fenghua Yu , "David S. Miller" , x86@kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Andy Lutomirski , Borislav Petkov , Mathias Krause , Jan Kara , Vitaly Wool , Andrea Arcangeli , Dmitry Vyukov , Laura Abbott , 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 On Fri, 2016-07-15 at 14:44 -0700, Kees Cook wrote: > Hi, >A > [I'm going to carry this series in my kspp -next tree now, though I'd > really love to have some explicit Acked-bys or Reviewed-bys. If you've > looked through it or tested it, please consider it. :) (I added Valdis > and mpe's Tested-bys where they seemed correct, thank you!)] >A > 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 and other people's feedback along > with other changes and clean-ups. >A > Based on my understanding, PAX_USERCOPY was designed to catch a > few classes of flaws (mainly bad bounds checking) 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).) >A > 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 > A 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 > A current stack frame (if such checking is possible) or at least entirely > A within the current process's stack. (This could catch large lengths that > A would have extended beyond the current process stack, or overflows if > A 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 > A allocations. > - if address is within the kernel text, reject it. > - everything else is accepted >A > The patches in the series are: > - Support for arch-specific stack frame checking (which will likely be > A replaced in the future by Josh's more comprehensive unwinder): > A A A A A A A A 1- mm: Implement stack frame object validation > - The core copy_to/from_user() checks, without the slab object checks: > A A A A A A A A 2- mm: Hardened usercopy > - Per-arch enablement of the protection: > A A A A A A A A 3- x86/uaccess: Enable hardened usercopy > A A A A A A A A 4- ARM: uaccess: Enable hardened usercopy > A A A A A A A A 5- arm64/uaccess: Enable hardened usercopy > A A A A A A A A 6- ia64/uaccess: Enable hardened usercopy > A A A A A A A A 7- powerpc/uaccess: Enable hardened usercopy > A A A A A A A A 8- sparc/uaccess: Enable hardened usercopy > A A A A A A A A 9- s390/uaccess: Enable hardened usercopy > - The heap allocator implementation of object size checking: > A A A A A A A 10- mm: SLAB hardened usercopy support > A A A A A A A 11- mm: SLUB hardened usercopy support >A > Some notes: >A > - This is expected to apply on top of -next which contains fixes for the > A position of _etext on both arm and arm64, though it has minor conflicts > A with KASAN that are trivial to fix up. Living in -next are also tests > A for this protection in lkdtm, prefixed with USERCOPY_. >A > - I couldn't detect a measurable performance change with these features > A enabled. Kernel build times were unchanged, hackbench was unchanged, > A etc. I think we could flip this to "on by default" at some point, but > A for now, I'm leaving it off until I can get some more definitive > A measurements. I would love if someone with greater familiarity with > A perf could give this a spin and report results. >A > - The SLOB support extracted from grsecurity seems entirely broken. I > A have no idea what's going on there, I spent my time testing SLAB and > A SLUB. Having someone else look at SLOB would be nice, but this series > A doesn't depend on it. >A > Additional features that would be nice, but aren't blocking this series: >A > - Needs more architecture support for stack frame checking (only x86 now, > A but it seems Josh will have a good solution for this soon). >A >A > Thanks! >A > -Kees >A > [1] https://grsecurity.net/download.php "grsecurity - test kernel patch" > [2] http://www.openwall.com/lists/kernel-hardening/2016/05/19/5 >A > v3: > - switch to using BUG for better Oops integration > - when checking page allocations, check each for Reserved > - use enums for the stack check return for readability > Thanks looks good so far! I'll try and test it and report back BalbirA -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org