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From: Kees Cook <keescook@chromium.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk,
	Emese Revfy <re.emese@gmail.com>, Arnd Bergmann <arnd@arndb.de>,
	Laura Abbott <labbott@redhat.com>,
	kernel-hardening@lists.openwall.com
Subject: Re: [PATCH v3] ARM: smp: add support for per-task stack canaries
Date: Wed, 11 Mar 2020 10:21:20 -0700	[thread overview]
Message-ID: <202003111020.D543B4332@keescook> (raw)
In-Reply-To: <20200309164931.GA23889@roeck-us.net>

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?

-- 
Kees Cook

  reply	other threads:[~2020-03-11 17:21 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-06  8:32 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 [this message]
2020-03-11 18:31     ` Guenter Roeck
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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