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From: Kees Cook <keescook@chromium.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Elena Reshetova <elena.reshetova@intel.com>,
	x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Alexander Potapenko <glider@google.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jann Horn <jannh@google.com>,
	"Perla, Enrico" <enrico.perla@intel.com>,
	kernel-hardening@lists.openwall.com,
	linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 5/5] arm64: entry: Enable random_kstack_offset support
Date: Wed, 25 Mar 2020 13:22:07 -0700	[thread overview]
Message-ID: <202003251319.AECA788D63@keescook> (raw)
In-Reply-To: <20200325132127.GB12236@lakrids.cambridge.arm.com>

On Wed, Mar 25, 2020 at 01:21:27PM +0000, Mark Rutland wrote:
> On Tue, Mar 24, 2020 at 01:32:31PM -0700, Kees Cook wrote:
> > Allow for a randomized stack offset on a per-syscall basis, with roughly
> > 5 bits of entropy.
> > 
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> 
> Just to check, do you have an idea of the impact on arm64? Patch 3 had
> figures for x86 where it reads the TSC, and it's unclear to me how
> get_random_int() compares to that.

I didn't do a measurement on arm64 since I don't have a good bare-metal
test environment. I know Andy Lutomirki has plans for making
get_random_get() as fast as possible, so that's why I used it here. I
couldn't figure out if there was a comparable instruction like rdtsc in
aarch64 (it seems there's a cycle counter, but I found nothing in the
kernel that seemed to actually use it)?

> Otherwise, this looks sound to me; I'd jsut like to know whether the
> overhead is in the same ballpark.

Thanks!

-Kees

-- 
Kees Cook

WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Jann Horn <jannh@google.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Alexander Potapenko <glider@google.com>,
	linux-arm-kernel@lists.infradead.org,
	Andy Lutomirski <luto@kernel.org>,
	kernel-hardening@lists.openwall.com, "Perla,
	Enrico" <enrico.perla@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Will Deacon <will@kernel.org>,
	Elena Reshetova <elena.reshetova@intel.com>
Subject: Re: [PATCH v2 5/5] arm64: entry: Enable random_kstack_offset support
Date: Wed, 25 Mar 2020 13:22:07 -0700	[thread overview]
Message-ID: <202003251319.AECA788D63@keescook> (raw)
In-Reply-To: <20200325132127.GB12236@lakrids.cambridge.arm.com>

On Wed, Mar 25, 2020 at 01:21:27PM +0000, Mark Rutland wrote:
> On Tue, Mar 24, 2020 at 01:32:31PM -0700, Kees Cook wrote:
> > Allow for a randomized stack offset on a per-syscall basis, with roughly
> > 5 bits of entropy.
> > 
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> 
> Just to check, do you have an idea of the impact on arm64? Patch 3 had
> figures for x86 where it reads the TSC, and it's unclear to me how
> get_random_int() compares to that.

I didn't do a measurement on arm64 since I don't have a good bare-metal
test environment. I know Andy Lutomirki has plans for making
get_random_get() as fast as possible, so that's why I used it here. I
couldn't figure out if there was a comparable instruction like rdtsc in
aarch64 (it seems there's a cycle counter, but I found nothing in the
kernel that seemed to actually use it)?

> Otherwise, this looks sound to me; I'd jsut like to know whether the
> overhead is in the same ballpark.

Thanks!

-Kees

-- 
Kees Cook

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-03-25 20:22 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24 20:32 [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall Kees Cook
2020-03-24 20:32 ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 1/5] jump_label: Provide CONFIG-driven build state defaults Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-24 22:06   ` Peter Zijlstra
2020-03-24 22:06     ` Peter Zijlstra
2020-03-24 20:32 ` [PATCH v2 2/5] init_on_alloc: Unpessimize default-on builds Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-26 15:48   ` Alexander Potapenko
2020-03-26 15:48     ` Alexander Potapenko
2020-03-26 15:48     ` Alexander Potapenko
2020-03-24 20:32 ` [PATCH v2 3/5] stack: Optionally randomize kernel stack offset each syscall Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-30 11:25   ` Mark Rutland
2020-03-30 11:25     ` Mark Rutland
2020-03-30 18:18     ` Kees Cook
2020-03-30 18:18       ` Kees Cook
2020-03-30 18:27     ` Kees Cook
2020-03-30 18:27       ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 4/5] x86/entry: Enable random_kstack_offset support Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-28 22:26   ` Kees Cook
2020-03-28 22:26     ` Kees Cook
2020-03-24 20:32 ` [PATCH v2 5/5] arm64: entry: " Kees Cook
2020-03-24 20:32   ` Kees Cook
2020-03-25 13:21   ` Mark Rutland
2020-03-25 13:21     ` Mark Rutland
2020-03-25 20:22     ` Kees Cook [this message]
2020-03-25 20:22       ` Kees Cook
2020-03-26 11:15       ` Mark Rutland
2020-03-26 11:15         ` Mark Rutland
2020-03-26 16:31         ` Kees Cook
2020-03-26 16:31           ` Kees Cook
2020-03-30 11:26           ` Mark Rutland
2020-03-30 11:26             ` Mark Rutland
2020-04-20 20:54   ` Will Deacon
2020-04-20 20:54     ` Will Deacon
2020-04-20 22:34     ` Kees Cook
2020-04-20 22:34       ` Kees Cook
2020-04-21  7:02       ` Will Deacon
2020-04-21  7:02         ` Will Deacon
2020-03-24 21:28 ` [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall Jann Horn
2020-03-24 21:28   ` Jann Horn
2020-03-24 21:28   ` Jann Horn
2020-03-24 23:07   ` Kees Cook
2020-03-24 23:07     ` Kees Cook
2020-03-25 12:15     ` Reshetova, Elena
2020-03-25 12:15       ` Reshetova, Elena
2020-03-25 12:15       ` Reshetova, Elena
2020-03-25 20:27       ` Kees Cook
2020-03-25 20:27         ` Kees Cook
2020-03-25 20:27         ` Kees Cook
2020-03-25 23:20         ` Jann Horn
2020-03-25 23:20           ` Jann Horn
2020-03-25 23:20           ` Jann Horn
2020-03-26 17:18           ` Kees Cook
2020-03-26 17:18             ` Kees Cook
2020-03-26 17:18             ` Kees Cook

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