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Message-ID: <20110919051239.GY6573@outflux.net>
Date: Sun, 18 Sep 2011 22:12:39 -0700
From: Kees Cook <kees@...ntu.com>
To: David Windsor <dwindsor@...il.com>
Cc: ubuntu-hardened@...ts.ubuntu.com, kernel-hardening@...ts.openwall.com
Subject: Re: Sysctl for set_kernel_text_r[wo]
Hi David,
On Sun, Sep 18, 2011 at 09:42:59PM -0400, David Windsor wrote:
> I am looking into adding a sysctl that enables toggling of
> set_kernel_text_rw, set_kernel_text_ro. It appears that the only
> caller of these methods is ftrace, which can rather easily be disabled
> when these methods are unavailable.
It would be really nice to be able to wipe these functions out. I really
dislike that they are available as such perfect ROP targets.
> I'm afraid I'm overlooking something major here. It seems that such a
> control would have been added much earlier if it was actually as
> simple as adding a guard variable, mutable via a sysctl, allowing
> access to this interface.
I haven't spent too much time looking into it, but I was under the
impression that the module loader used some of the underlying functions
too. Have you checked those code paths?
-Kees
--
Kees Cook
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