From: Helge Deller <deller@gmx.de>
To: Heiko Carstens <heiko.carstens@de.ibm.com>,
Mark Rutland <mark.rutland@arm.com>
Cc: Laura Abbott <labbott@redhat.com>,
Kees Cook <keescook@chromium.org>,
Jason Wessel <jason.wessel@windriver.com>,
Jonathan Corbet <corbet@lwn.net>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
"James E.J. Bottomley" <jejb@parisc-linux.org>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Rob Herring <robh@kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
Jessica Yu <jeyu@redhat.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org,
linux-pm@vger.kernel.org, kernel-hardening@lists.openwall.com
Subject: Re: [PATCH 1/2] security: Change name of CONFIG_DEBUG_RODATA
Date: Thu, 19 Jan 2017 22:17:12 +0100 [thread overview]
Message-ID: <a3c9b67f-9b10-15d5-c00f-7b8a98d11001@gmx.de> (raw)
In-Reply-To: <20170119113305.GB5110@osiris>
On 19.01.2017 12:33, Heiko Carstens wrote:
> On Thu, Jan 19, 2017 at 10:56:46AM +0000, Mark Rutland wrote:
>>> +config HARDENED_PAGE_MAPPINGS
>>> + bool "Mark kernel mappings with stricter permissions (RO/W^X)"
>>> + default y
>>> + depends on ARCH_HAS_HARDENED_MAPPINGS
>>> + help
>>> + If this is set, kernel text and rodata memory will be made read-only,
>>> + and non-text memory will be made non-executable. This provides
>>> + protection against certain security attacks (e.g. executing the heap
>>> + or modifying text).
>>> +
>>> + Unless your system has known restrictions or performance issues, it
>>> + is recommended to say Y here.
>>
>> It's somewhat unfortunate that this means the feature is no longer
>> mandatory on arm64 (and s390+x86). We have a boot-time switch to turn
>> the protections off, so I was hoping we could make this mandatory on all
>> architectures with support.
>>
>> It would be good to see if we could make this mandatory for arm and
>> parisc, or if it really needs to be optional for either of those.
>
> Looks like the config option is a no-op on parisc just like it is on
> s390. Irrelavant of the config option at least on s390 the page tables for
> kernel text and rodata will be read-only anyway.
Right, that's true at the moment for parisc as well.
I do have unfinished patches which will add runtime kernel patching
for ftrace to parisc, and those patches will need to add code to
enable/disable ro text/data like x86.
> This works since ages and I don't see a reason why this should be
> changed. Also trying to disable this with the "rodata=" command line option
> does not work at least on s390, and I guess this is true for parisc as
> well.
I never tried the option itself, but it should work on parisc to disable
the ro protection by this option.
> The only thing implemented with CONFIG_DEBUG_RODATA on both architectures
> is to emit a message that states memory has been protected
> (mark_rodata_ro).
> This just avoids a wrong "Kernel memory protection disabled." message.
>
> So yes, I'd really like to keep this option mandatory.
I'd be fine with a rename of the config option to ARCH_HAS_HARDENED_MAPPINGS
and keeping the "rodata=" command line.
Helge
next prev parent reply other threads:[~2017-01-19 21:19 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-19 1:29 [RFC][PATCH 0/2] Better hardening names Laura Abbott
2017-01-19 1:29 ` [PATCH 1/2] security: Change name of CONFIG_DEBUG_RODATA Laura Abbott
2017-01-19 7:53 ` Pavel Machek
2017-01-25 11:21 ` Laura Abbott
2017-01-25 13:51 ` Pavel Machek
2017-01-19 10:56 ` Mark Rutland
2017-01-19 11:33 ` Heiko Carstens
2017-01-19 21:17 ` Helge Deller [this message]
2017-01-25 11:37 ` Laura Abbott
2017-01-19 22:00 ` Kees Cook
2017-01-25 11:25 ` Laura Abbott
2017-01-19 21:57 ` Kees Cook
2017-01-19 1:29 ` [PATCH 2/2] security: Change name of CONFIG_DEBUG_SET_MODULE_RONX Laura Abbott
2017-01-19 11:11 ` Mark Rutland
2017-01-19 11:34 ` Heiko Carstens
2017-01-19 11:43 ` Robin Murphy
2017-01-25 11:44 ` Laura Abbott
2017-01-20 5:46 ` kbuild test robot
2017-01-19 22:08 ` [RFC][PATCH 0/2] Better hardening names Kees Cook
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