From: Arnd Bergmann <arnd@arndb.de>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Kees Cook <keescook@chromium.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>,
Laura Abbott <labbott@redhat.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
Nicolas Pitre <nicolas.pitre@linaro.org>,
Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH v2 04/20] gcc-plugins: Add the randstruct plugin
Date: Fri, 30 Jun 2017 10:27:06 +0200 [thread overview]
Message-ID: <CAK8P3a076DEDpzRgTRBNLWan-KZyD0LkauWpuO8RFCf-9i1mhA@mail.gmail.com> (raw)
In-Reply-To: <CAKv+Gu-EWyfB3zbPwT9=bLwR0GDtg5mwKaD0p5AbssjbxU7sMA@mail.gmail.com>
On Fri, Jun 30, 2017 at 9:55 AM, Ard Biesheuvel
<ard.biesheuvel@linaro.org> wrote:
> On 30 June 2017 at 07:35, Arnd Bergmann <arnd@arndb.de> wrote:
>> On Fri, Jun 30, 2017 at 12:53 AM, Kees Cook <keescook@chromium.org> wrote:
>>> The first obviously won't fly. The second just bypasses the problem
>>> forcing it to be exposed by other people later. The third is likely
>>> easiest to do now, but reduces the effectiveness of randomization for
>>> architectures that don't have sensitive immediate values. The fourth
>>> sounds not generally useful. The fifth may be unacceptable to arm
>>> maintainers due to performance impacts.
>>
>> I was thinking of the fifth solution, but don't know exactly how to
>> do it. If performance is a concern, I guess we could have separate
>> implementations for randstruct and traditional builds.
>>
>
> Does this not apply to *all* entries in asm-offsets? If so, I don't
> see how it is tractable to fix this in the code, unless we add some
> instrumentation to asm-offsets to whitelist some huge structs and
> error out on new ones. Or perhaps there's really only a handful?
I think the other structs are all small enough:
* thread_info is at most 720 bytes (including crunch+vfp3, which
you wouldn't find in one combined kernel) and not randomized
at the moment
* pt_regs is 72 bytes and I don't see how that would be randomized
* machine_desc would be a candidate for randomizing, but is only
108 bytes
* proc_info_list is 52 bytes and not currently randomized
* vm_area_struct is randomized but only 96 bytes.
* task_struct is clearly large enough, but we only use TSK_ACTIVE_MM
and TSK_STACK_CANARY, both can be fixed with your trick.
> In any case, these particular examples are fairly straightforward,
> since there is no need to preserve the register's value.
>
> ldr r7, [r7, #TSK_STACK_CANARY]
>
> could be replaced with
>
> .if TSK_STACK_CANARAY >= PAGE_SIZE
> add r7, r7, #TSK_STACK_CANARY & PAGE_MASK
> .endif
> ldr r7, [r7, #TSK_STACK_CANARY & ~PAGE_MASK]
Nice!
Arnd
next prev parent reply other threads:[~2017-06-30 8:27 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-26 20:17 [PATCH v2 00/20] Introduce struct layout randomization plugin Kees Cook
2017-05-26 20:17 ` [PATCH v2 01/20] NFS: Avoid cross-structure casting Kees Cook
2017-05-28 7:53 ` Christoph Hellwig
2017-05-28 16:55 ` Kees Cook
2017-05-26 20:17 ` [PATCH v2 02/20] gcc-plugins: Detail c-common.h location for GCC 4.6 Kees Cook
2017-05-26 20:17 ` [PATCH v2 03/20] compiler: Add __designated_init annotation Kees Cook
2017-05-26 20:17 ` [PATCH v2 04/20] gcc-plugins: Add the randstruct plugin Kees Cook
2017-06-29 22:08 ` Arnd Bergmann
2017-06-29 22:53 ` Kees Cook
2017-06-30 0:04 ` Kees Cook
2017-06-30 7:35 ` Arnd Bergmann
2017-06-30 7:55 ` Ard Biesheuvel
2017-06-30 8:27 ` Arnd Bergmann [this message]
2017-06-30 14:41 ` Kees Cook
2017-06-30 15:22 ` Arnd Bergmann
2017-05-26 20:17 ` [PATCH v2 05/20] randstruct: Whitelist struct security_hook_heads cast Kees Cook
2017-05-27 8:41 ` Christoph Hellwig
2017-05-27 20:09 ` Kees Cook
2017-05-27 22:04 ` Tetsuo Handa
2017-05-28 0:43 ` [kernel-hardening] " Kees Cook
2017-05-30 10:34 ` James Morris
2017-05-26 20:17 ` [PATCH v2 06/20] randstruct: Whitelist UNIXCB cast Kees Cook
2017-05-26 20:20 ` Kees Cook
2017-05-28 7:56 ` Christoph Hellwig
2017-05-26 20:17 ` [PATCH v2 07/20] randstruct: Whitelist big_key path struct overloading Kees Cook
2017-05-28 8:12 ` Christoph Hellwig
2017-05-28 16:59 ` Kees Cook
2017-06-19 19:24 ` Kees Cook
2017-09-07 7:20 ` Christoph Hellwig
2017-09-07 22:55 ` Kees Cook
2017-05-26 20:17 ` [PATCH v2 08/20] randstruct: Whitelist NIU struct page overloading Kees Cook
2017-05-28 8:15 ` Christoph Hellwig
2017-05-28 17:35 ` Kees Cook
2017-05-28 17:37 ` Kees Cook
2017-05-26 20:17 ` [PATCH v2 09/20] randstruct: Mark various structs for randomization Kees Cook
2017-05-26 20:17 ` [PATCH v2 10/20] randstruct: opt-out externally exposed function pointer structs Kees Cook
2017-05-26 20:17 ` [PATCH v2 11/20] randstruct: Disable randomization of ACPICA structs Kees Cook
2017-05-27 8:42 ` Christoph Hellwig
2017-05-27 20:03 ` Kees Cook
2017-05-28 4:55 ` Christoph Hellwig
2017-05-26 20:17 ` [PATCH v2 12/20] sgi-xp: Use designated initializers Kees Cook
2017-05-27 8:44 ` Christoph Hellwig
2017-05-26 20:17 ` [PATCH v2 13/20] drm/amdgpu: " Kees Cook
2017-05-26 20:17 ` [PATCH v2 14/20] drm/amd/powerplay: " Kees Cook
2017-05-27 8:47 ` Christoph Hellwig
2017-05-27 20:10 ` Kees Cook
2017-05-26 20:17 ` [PATCH v2 15/20] mtk-vcodec: " Kees Cook
2017-05-26 20:17 ` [PATCH v2 16/20] ntfs: Use ERR_CAST() to avoid cross-structure cast Kees Cook
2017-05-26 20:17 ` [PATCH v2 17/20] ocfs2: " Kees Cook
2017-05-26 20:17 ` [PATCH v2 18/20] randstruct: Enable function pointer struct detection Kees Cook
2017-05-26 20:17 ` [PATCH v2 19/20] [RFC] task_struct: Allow randomized layout Kees Cook
2017-05-26 20:23 ` Linus Torvalds
2017-05-26 20:32 ` Kees Cook
2017-05-26 20:17 ` [PATCH v2 20/20] ACPICA: Use designated initializers Kees Cook
2017-05-28 7:45 ` Christoph Hellwig
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