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From: Kees Cook <keescook@chromium.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: 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>
Subject: Re: [PATCH v2 04/20] gcc-plugins: Add the randstruct plugin
Date: Thu, 29 Jun 2017 17:04:46 -0700	[thread overview]
Message-ID: <CAGXu5j+P7Sj99DdYE0mL1fjzVUoK6qntJXhSLk-vnKhHjejd7g@mail.gmail.com> (raw)
In-Reply-To: <CAGXu5jJHRC83YSDKVfm4_41k0wgqfG=wpqPQss-ce77SRNkwRA@mail.gmail.com>

On Thu, Jun 29, 2017 at 3:53 PM, Kees Cook <keescook@chromium.org> wrote:
> I see a few possible solutions:

Or this ugly hack:

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e2ad3531e7fe..5d131f9f1dac 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -749,6 +749,19 @@ struct task_struct {
        /* Namespaces: */
        struct nsproxy                  *nsproxy;

+#ifdef CONFIG_ARM
+       /*
+        * Since task_struct is gigantic, some asmoffset locations
+        * (e.g. TSK_STACK_CANARY) for a randomized field may exceed
+        * an architecture's instruction immediate values. As a
+        * work-around to avoid changing the performance characteristics
+        * of the assembly, split the randomization into two groups,
+        * keeping the "early" fields within range of the immediates.
+        */
+       randomized_struct_fields_end
+       randomized_struct_fields_start
+#endif
+
        /* Signal handlers: */
        struct signal_struct            *signal;
        struct sighand_struct           *sighand;


I suspect updating the ARM assembly (CONFIG-conditionally) to accept
>4095 offsets is probably the best solution.

-Kees

-- 
Kees Cook
Pixel Security

  reply	other threads:[~2017-06-30  0:05 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 [this message]
2017-06-30  7:35       ` Arnd Bergmann
2017-06-30  7:55         ` Ard Biesheuvel
2017-06-30  8:27           ` Arnd Bergmann
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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