From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Laura Abbott <labbott@redhat.com>
Cc: Kees Cook <keescook@chromium.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Rik van Riel <riel@redhat.com>,
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>,
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>,
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-arm-kernel@lists.infradead.org>,
"linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
sparclinux@vger.kernel.org,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
kernel-hardening@lists.openwall.com
Subject: Re: [PATCH 0/9] mm: Hardened usercopy
Date: Sat, 9 Jul 2016 10:25:00 +0200 [thread overview]
Message-ID: <CAKv+Gu_F03ncqT2wWFte2bFWQ7tSruL0ZaxTBLT9_NEs-1SioQ@mail.gmail.com> (raw)
In-Reply-To: <b113b487-acc6-24b8-d58c-425d3c884f4c@redhat.com>
On 9 July 2016 at 04:22, Laura Abbott <labbott@redhat.com> wrote:
> On 07/06/2016 03:25 PM, 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
>> - The heap allocator implementation of object size checking:
>> 8- mm: SLAB hardened usercopy support
>> 9- mm: SLUB hardened usercopy support
>>
>> Some notes:
>>
>> - This is expected to apply on top of -next which contains fixes for the
>> position of _etext on both arm and arm64.
>>
>> - I couldn't detect a measurable performance change with these features
>> enabled. Kernel build times were unchanged, hackbench was unchanged,
>> etc. I think we could flip this to "on by default" at some point.
>>
>> - The SLOB support extracted from grsecurity seems entirely broken. I
>> have no idea what's going on there, I spent my time testing SLAB and
>> SLUB. Having someone else look at SLOB would be nice, but this series
>> doesn't depend on it.
>>
>> Additional features that would be nice, but aren't blocking this series:
>>
>> - Needs more architecture support for stack frame checking (only x86 now).
>>
>>
>
> Even with the SLUB fixup I'm still seeing this blow up on my arm64 system.
> This is a
> Fedora rawhide kernel + the patches
>
> [ 0.666700] usercopy: kernel memory exposure attempt detected from
> fffffc0008b4dd58 (<kernel text>) (8 bytes)
> [ 0.666720] CPU: 2 PID: 79 Comm: modprobe Tainted: G W
> 4.7.0-0.rc6.git1.1.hardenedusercopy.fc25.aarch64 #1
> [ 0.666733] Hardware name: AppliedMicro Mustang/Mustang, BIOS 1.1.0 Nov 24
> 2015
> [ 0.666744] Call trace:
> [ 0.666756] [<fffffc0008088a20>] dump_backtrace+0x0/0x1e8
> [ 0.666765] [<fffffc0008088c2c>] show_stack+0x24/0x30
> [ 0.666775] [<fffffc0008455344>] dump_stack+0xa4/0xe0
> [ 0.666785] [<fffffc000828d874>] __check_object_size+0x6c/0x230
> [ 0.666795] [<fffffc00083a5748>] create_elf_tables+0x74/0x420
> [ 0.666805] [<fffffc00082fb1f0>] load_elf_binary+0x828/0xb70
> [ 0.666814] [<fffffc0008298b4c>] search_binary_handler+0xb4/0x240
> [ 0.666823] [<fffffc0008299864>] do_execveat_common+0x63c/0x950
> [ 0.666832] [<fffffc0008299bb4>] do_execve+0x3c/0x50
> [ 0.666841] [<fffffc00080e3720>] call_usermodehelper_exec_async+0xe8/0x148
> [ 0.666850] [<fffffc0008084a80>] ret_from_fork+0x10/0x50
>
> This happens on every call to execve. This seems to be the first
> copy_to_user in
> create_elf_tables. I didn't get a chance to debug and I'm going out of town
> all of next week so all I have is the report unfortunately. config attached.
>
This is a known issue, and a fix is already queued for v4.8 in the arm64 tree:
9fdc14c55c arm64: mm: fix location of _etext [0]
which moves _etext up in the linker script so that it does not cover .rodata
ARM was suffering from the same problem, and Kees proposed a fix for
it. I don't know what the status of that patch is, though.
Note that on arm64, we have
#define ELF_PLATFORM ("aarch64")
which explains why k_platform points into .rodata in this case. On
ARM, it points to a writable string (as the code quoted by Rik shows),
so there it will likely explode elsewhere without the linker script
fix.
[0] https://git.kernel.org/cgit/linux/kernel/git/arm64/linux.git/commit/?h=for-next/core&id=9fdc14c55c
--
Ard.
next prev parent reply other threads:[~2016-07-09 8:25 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-06 22:25 [PATCH 0/9] mm: Hardened usercopy Kees Cook
2016-07-06 22:25 ` [PATCH 1/9] " Kees Cook
2016-07-07 5:37 ` Baruch Siach
2016-07-07 17:25 ` Kees Cook
2016-07-07 18:35 ` Baruch Siach
2016-07-07 7:42 ` Thomas Gleixner
2016-07-07 17:29 ` Kees Cook
2016-07-07 19:34 ` Thomas Gleixner
2016-07-07 8:01 ` Arnd Bergmann
2016-07-07 17:37 ` Kees Cook
2016-07-08 5:34 ` Michael Ellerman
2016-07-08 9:22 ` Arnd Bergmann
2016-07-07 16:19 ` Rik van Riel
2016-07-07 16:35 ` Rik van Riel
2016-07-07 17:41 ` Kees Cook
2016-07-06 22:25 ` [PATCH 2/9] x86/uaccess: Enable hardened usercopy Kees Cook
2016-07-06 22:25 ` [PATCH 3/9] ARM: uaccess: " Kees Cook
2016-07-06 22:25 ` [PATCH 4/9] arm64/uaccess: " Kees Cook
2016-07-07 10:07 ` Mark Rutland
2016-07-07 17:19 ` Kees Cook
2016-07-06 22:25 ` [PATCH 5/9] ia64/uaccess: " Kees Cook
2016-07-06 22:25 ` [PATCH 6/9] powerpc/uaccess: " Kees Cook
2016-07-06 22:25 ` [PATCH 7/9] sparc/uaccess: " Kees Cook
2016-07-06 22:25 ` [PATCH 8/9] mm: SLAB hardened usercopy support Kees Cook
2016-07-06 22:25 ` [PATCH 9/9] mm: SLUB " Kees Cook
2016-07-07 4:35 ` Michael Ellerman
[not found] ` <577ddc18.d351190a.1fa54.ffffbe79SMTPIN_ADDED_BROKEN@mx.google.com>
2016-07-07 18:56 ` [kernel-hardening] " Kees Cook
2016-07-08 10:19 ` Michael Ellerman
2016-07-08 13:45 ` Christoph Lameter
2016-07-08 16:07 ` Kees Cook
2016-07-08 16:20 ` Christoph Lameter
2016-07-08 17:41 ` Kees Cook
2016-07-08 20:48 ` Kees Cook
2016-07-09 5:58 ` Michael Ellerman
2016-07-09 6:07 ` Michael Ellerman
[not found] ` <57809299.84b3370a.5390c.ffff9e58SMTPIN_ADDED_BROKEN@mx.google.com>
2016-07-09 6:17 ` Valdis.Kletnieks
2016-07-09 17:07 ` Kees Cook
2016-07-11 6:08 ` Joonsoo Kim
2016-07-07 7:30 ` [PATCH 0/9] mm: Hardened usercopy Christian Borntraeger
2016-07-07 17:27 ` Kees Cook
2016-07-08 8:46 ` Ingo Molnar
2016-07-08 16:19 ` Linus Torvalds
2016-07-08 18:23 ` Ingo Molnar
2016-07-09 2:22 ` Laura Abbott
2016-07-09 2:44 ` Rik van Riel
2016-07-09 7:55 ` Ingo Molnar
2016-07-09 8:25 ` Ard Biesheuvel [this message]
2016-07-09 12:58 ` Laura Abbott
2016-07-09 17:03 ` Kees Cook
2016-07-09 17:01 ` Kees Cook
2016-07-09 21:27 ` Andy Lutomirski
2016-07-09 23:16 ` PaX Team
2016-07-10 9:16 ` Ingo Molnar
2016-07-10 12:03 ` PaX Team
2016-07-10 12:38 ` Andy Lutomirski
2016-07-11 18:40 ` Kees Cook
2016-07-11 18:34 ` Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAKv+Gu_F03ncqT2wWFte2bFWQ7tSruL0ZaxTBLT9_NEs-1SioQ@mail.gmail.com \
--to=ard.biesheuvel@linaro.org \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=benh@kernel.crashing.org \
--cc=bp@suse.de \
--cc=casey@schaufler-ca.com \
--cc=catalin.marinas@arm.com \
--cc=cl@linux.com \
--cc=davem@davemloft.net \
--cc=dvyukov@google.com \
--cc=fenghua.yu@intel.com \
--cc=iamjoonsoo.kim@lge.com \
--cc=jack@suse.cz \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=labbott@fedoraproject.org \
--cc=labbott@redhat.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux@armlinux.org.uk \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=luto@kernel.org \
--cc=minipli@googlemail.com \
--cc=mpe@ellerman.id.au \
--cc=pageexec@freemail.hu \
--cc=penberg@kernel.org \
--cc=riel@redhat.com \
--cc=rientjes@google.com \
--cc=sparclinux@vger.kernel.org \
--cc=spender@grsecurity.net \
--cc=tony.luck@intel.com \
--cc=vitalywool@gmail.com \
--cc=will.deacon@arm.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).