From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org,
Kees Cook <keescook@chromium.org>,
linux-arch <linux-arch@vger.kernel.org>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
"x86@kernel.org" <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mathias Krause <minipli@googlemail.com>
Subject: [kernel-hardening] Re: [PATCH 2/2] arm: apply more __ro_after_init
Date: Thu, 11 Aug 2016 00:06:45 +0100 [thread overview]
Message-ID: <20160810230645.GP1041@n2100.armlinux.org.uk> (raw)
In-Reply-To: <2760702.46Rp2Juk5b@wuerfel>
On Wed, Aug 10, 2016 at 09:41:23PM +0200, Arnd Bergmann wrote:
> It might be better to start by making the fixed mapping readonly,
> as KASLR doesn't protect that one at all, and change the TLS
> code accordingly.
I think that's impossible, because we gave userspace permission to
read 0xffff0ff0 directly without using __kuser_get_tls. You're
talking about potentially breaking userspace.
If you disable kuser helpers, then the page becomes read-only and
invisible to userspace anyway. So, everything is being done there
which can be done - if you have kuser helpers enabled, then you
lose some opportunities for these security improvements.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
WARNING: multiple messages have this Message-ID (diff)
From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org,
Kees Cook <keescook@chromium.org>,
linux-arch <linux-arch@vger.kernel.org>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
"x86@kernel.org" <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mathias Krause <minipli@googlemail.com>
Subject: Re: [PATCH 2/2] arm: apply more __ro_after_init
Date: Thu, 11 Aug 2016 00:06:45 +0100 [thread overview]
Message-ID: <20160810230645.GP1041@n2100.armlinux.org.uk> (raw)
In-Reply-To: <2760702.46Rp2Juk5b@wuerfel>
On Wed, Aug 10, 2016 at 09:41:23PM +0200, Arnd Bergmann wrote:
> It might be better to start by making the fixed mapping readonly,
> as KASLR doesn't protect that one at all, and change the TLS
> code accordingly.
I think that's impossible, because we gave userspace permission to
read 0xffff0ff0 directly without using __kuser_get_tls. You're
talking about potentially breaking userspace.
If you disable kuser helpers, then the page becomes read-only and
invisible to userspace anyway. So, everything is being done there
which can be done - if you have kuser helpers enabled, then you
lose some opportunities for these security improvements.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
WARNING: multiple messages have this Message-ID (diff)
From: linux@armlinux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] arm: apply more __ro_after_init
Date: Thu, 11 Aug 2016 00:06:45 +0100 [thread overview]
Message-ID: <20160810230645.GP1041@n2100.armlinux.org.uk> (raw)
In-Reply-To: <2760702.46Rp2Juk5b@wuerfel>
On Wed, Aug 10, 2016 at 09:41:23PM +0200, Arnd Bergmann wrote:
> It might be better to start by making the fixed mapping readonly,
> as KASLR doesn't protect that one at all, and change the TLS
> code accordingly.
I think that's impossible, because we gave userspace permission to
read 0xffff0ff0 directly without using __kuser_get_tls. You're
talking about potentially breaking userspace.
If you disable kuser helpers, then the page becomes read-only and
invisible to userspace anyway. So, everything is being done there
which can be done - if you have kuser helpers enabled, then you
lose some opportunities for these security improvements.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2016-08-10 23:06 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-03 18:40 [kernel-hardening] [PATCH 0/2] expand use of __ro_after_init Kees Cook
2016-06-03 18:40 ` Kees Cook
2016-06-03 18:40 ` Kees Cook
2016-06-03 18:40 ` [kernel-hardening] [PATCH 1/2] x86: apply more __ro_after_init and const Kees Cook
2016-06-03 18:40 ` Kees Cook
2016-06-03 18:40 ` Kees Cook
2016-06-03 18:40 ` [kernel-hardening] [PATCH 2/2] arm: apply more __ro_after_init Kees Cook
2016-06-03 18:40 ` Kees Cook
2016-06-03 18:40 ` Kees Cook
2016-06-03 18:51 ` [kernel-hardening] " Greg KH
2016-06-03 18:51 ` Greg KH
2016-06-03 21:26 ` Kees Cook
2016-06-03 21:26 ` Kees Cook
2016-06-03 21:26 ` Kees Cook
2016-06-03 21:54 ` [kernel-hardening] " Greg KH
2016-06-03 21:54 ` Greg KH
2016-06-03 22:01 ` Kees Cook
2016-06-03 22:01 ` Kees Cook
2016-06-03 22:01 ` Kees Cook
2016-08-10 9:43 ` [kernel-hardening] " Russell King - ARM Linux
2016-08-10 9:43 ` Russell King - ARM Linux
2016-08-10 9:43 ` Russell King - ARM Linux
2016-08-10 10:00 ` [kernel-hardening] " Arnd Bergmann
2016-08-10 10:00 ` Arnd Bergmann
2016-08-10 10:00 ` Arnd Bergmann
2016-08-10 10:12 ` [kernel-hardening] " Russell King - ARM Linux
2016-08-10 10:12 ` Russell King - ARM Linux
2016-08-10 10:12 ` Russell King - ARM Linux
2016-08-10 19:31 ` [kernel-hardening] " Arnd Bergmann
2016-08-10 19:31 ` Arnd Bergmann
2016-08-10 19:31 ` Arnd Bergmann
2016-08-10 23:02 ` [kernel-hardening] " Russell King - ARM Linux
2016-08-10 23:02 ` Russell King - ARM Linux
2016-08-10 23:02 ` Russell King - ARM Linux
2016-08-11 16:02 ` [kernel-hardening] " Arnd Bergmann
2016-08-11 16:02 ` Arnd Bergmann
2016-08-11 16:02 ` Arnd Bergmann
2016-08-11 16:02 ` Arnd Bergmann
2016-08-11 16:02 ` Arnd Bergmann
2016-08-12 11:34 ` [kernel-hardening] " Daniel Thompson
2016-08-12 11:34 ` Daniel Thompson
2016-08-12 11:34 ` Daniel Thompson
2016-08-12 11:34 ` Daniel Thompson
2016-08-10 17:06 ` [kernel-hardening] " Daniel Micay
2016-08-10 17:06 ` Daniel Micay
2016-08-10 17:06 ` Daniel Micay
2016-08-10 18:32 ` [kernel-hardening] " Kees Cook
2016-08-10 18:32 ` Kees Cook
2016-08-10 18:32 ` Kees Cook
2016-08-10 19:41 ` [kernel-hardening] " Arnd Bergmann
2016-08-10 19:41 ` Arnd Bergmann
2016-08-10 19:41 ` Arnd Bergmann
2016-08-10 21:40 ` [kernel-hardening] " Kees Cook
2016-08-10 21:40 ` Kees Cook
2016-08-10 21:40 ` Kees Cook
2016-08-10 23:06 ` Russell King - ARM Linux [this message]
2016-08-10 23:06 ` Russell King - ARM Linux
2016-08-10 23:06 ` Russell King - ARM Linux
2016-08-11 15:54 ` [kernel-hardening] " Arnd Bergmann
2016-08-11 15:54 ` Arnd Bergmann
2016-08-11 15:54 ` Arnd Bergmann
2016-08-11 22:16 ` [kernel-hardening] " Kees Cook
2016-08-11 22:16 ` Kees Cook
2016-08-11 22:16 ` Kees Cook
2016-08-12 16:24 ` [kernel-hardening] " Russell King - ARM Linux
2016-08-12 16:24 ` Russell King - ARM Linux
2016-08-12 16:24 ` Russell King - ARM Linux
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