From: Guenter Roeck <linux@roeck-us.net>
To: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
kernel-hardening@lists.openwall.com, linux@armlinux.org.uk,
linux-kernel@vger.kernel.org, Emese Revfy <re.emese@gmail.com>,
Laura Abbott <labbott@redhat.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3] ARM: smp: add support for per-task stack canaries
Date: Wed, 11 Mar 2020 11:31:13 -0700 [thread overview]
Message-ID: <04a8c31a-3c43-3dcf-c9fd-82ba225a19f6@roeck-us.net> (raw)
In-Reply-To: <202003111020.D543B4332@keescook>
On 3/11/20 10:21 AM, Kees Cook wrote:
> On Mon, Mar 09, 2020 at 09:49:31AM -0700, Guenter Roeck wrote:
>> On Thu, Dec 06, 2018 at 09:32:57AM +0100, Ard Biesheuvel wrote:
>>> On ARM, we currently only change the value of the stack canary when
>>> switching tasks if the kernel was built for UP. On SMP kernels, this
>>> is impossible since the stack canary value is obtained via a global
>>> symbol reference, which means
>>> a) all running tasks on all CPUs must use the same value
>>> b) we can only modify the value when no kernel stack frames are live
>>> on any CPU, which is effectively never.
>>>
>>> So instead, use a GCC plugin to add a RTL pass that replaces each
>>> reference to the address of the __stack_chk_guard symbol with an
>>> expression that produces the address of the 'stack_canary' field
>>> that is added to struct thread_info. This way, each task will use
>>> its own randomized value.
>>>
>>> Cc: Russell King <linux@armlinux.org.uk>
>>> Cc: Kees Cook <keescook@chromium.org>
>>> Cc: Emese Revfy <re.emese@gmail.com>
>>> Cc: Arnd Bergmann <arnd@arndb.de>
>>> Cc: Laura Abbott <labbott@redhat.com>
>>> Cc: kernel-hardening@lists.openwall.com
>>> Acked-by: Nicolas Pitre <nico@linaro.org>
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>
>> Since this patch is in the tree, cc-option no longer works on
>> the arm architecture if CONFIG_STACKPROTECTOR_PER_TASK is enabled.
>>
>> Any idea how to fix that ?
>
> I thought Arnd sent a patch to fix it and it got picked up?
>
Yes, but the fix is not upstream (it is only in -next), and I missed it.
Guenter
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next prev parent reply other threads:[~2020-03-11 18:31 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-06 8:32 [PATCH v3] ARM: smp: add support for per-task stack canaries Ard Biesheuvel
2018-12-09 10:28 ` kbuild test robot
2018-12-09 10:37 ` Russell King - ARM Linux
2018-12-10 22:34 ` Kees Cook
2018-12-12 21:26 ` Kees Cook
2018-12-13 2:53 ` [kbuild-all] " Rong Chen
[not found] ` <235f0830-a293-5b00-4510-7d7d4c829d26@intel.com>
2019-01-09 21:37 ` Kees Cook
2020-03-09 16:49 ` Guenter Roeck
2020-03-11 17:21 ` Kees Cook
2020-03-11 18:31 ` Guenter Roeck [this message]
2020-03-11 18:47 ` Kees Cook
2020-03-11 20:45 ` Russell King - ARM Linux admin
2020-03-11 21:39 ` Guenter Roeck
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