Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 19 Jan 2017 12:33:05 +0100
From: Heiko Carstens <>
To: Mark Rutland <>
Cc: Laura Abbott <>, Kees Cook <>,
        Jason Wessel <>,
        Jonathan Corbet <>, Russell King <>,
        Catalin Marinas <>,
        Will Deacon <>,
        "James E.J. Bottomley" <>,
        Helge Deller <>,
        Martin Schwidefsky <>,
        Thomas Gleixner <>, Ingo Molnar <>,
        "H. Peter Anvin" <>,,
        Rob Herring <>, "Rafael J. Wysocki" <>,
        Len Brown <>, Pavel Machek <>,
        Jessica Yu <>,,,,,,,
Subject: Re: [PATCH 1/2] security: Change name of CONFIG_DEBUG_RODATA

On Thu, Jan 19, 2017 at 10:56:46AM +0000, Mark Rutland wrote:
> > +	bool "Mark kernel mappings with stricter permissions (RO/W^X)"
> > +	default y
> > +	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.

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

The only thing implemented with CONFIG_DEBUG_RODATA on both architectures
is to emit a message that states memory has been protected
This just avoids a wrong "Kernel memory protection disabled." message.

So yes, I'd really like to keep this option mandatory.

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.