From: keescook@chromium.org (Kees Cook)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/9] mm: Hardened usercopy
Date: Sat, 9 Jul 2016 10:01:18 -0700 [thread overview]
Message-ID: <CAGXu5jJVQCMZQm-zT07Siniiic9DSK7ZC=qdDMgFLwBpfEqYSg@mail.gmail.com> (raw)
In-Reply-To: <b113b487-acc6-24b8-d58c-425d3c884f4c@redhat.com>
On Fri, Jul 8, 2016 at 7:22 PM, 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
Is this on top of -next? The recent _etext change ("arm64: mm: fix
location of _etext") is needed to fix the kernel text test for arm64.
-Kees
>
> [ 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.
>
> Thanks,
> Laura
--
Kees Cook
Chrome OS & Brillo Security
next prev parent reply other threads:[~2016-07-09 17:01 UTC|newest]
Thread overview: 41+ 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 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 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
[not found] ` <b113b487-acc6-24b8-d58c-425d3c884f4c@redhat.com>
2016-07-09 2:44 ` Rik van Riel
2016-07-09 7:55 ` Ingo Molnar
2016-07-09 8:25 ` Ard Biesheuvel
2016-07-09 17:03 ` Kees Cook
2016-07-09 17:01 ` Kees Cook [this message]
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
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