linux-kernel - Re: [RFC PATCH 09/11] kallsyms: hide layout and expose seed

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Date:   Mon, 02 Mar 2020 11:19:55 -0800
From:   Kristen Carlson Accardi <kristen@...ux.intel.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Jann Horn <jannh@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [RFC PATCH 09/11] kallsyms: hide layout and expose seed

On Mon, 2020-03-02 at 11:08 -0800, Kees Cook wrote:
> On Mon, Mar 02, 2020 at 11:01:56AM -0800, Kristen Carlson Accardi
> wrote:
> > On Thu, 2020-02-06 at 20:27 +0100, Jann Horn wrote:
> > > https://codesearch.debian.net/search?q=%2Fproc%2Fkallsyms&literal=1
> > 
> > I looked through some of these packages as Jann suggested, and it
> > seems
> > like there are several that are using /proc/kallsyms to look for
> > specific symbol names to determine whether some feature has been
> > compiled into the kernel. This practice seems dubious to me,
> > knowing
> > that many kernel symbol names can be changed at any time, but
> > regardless seems to be fairly common.
> 
> Cool, so a sorted censored list is fine for non-root. Would root
> users
> break on a symbol-name-sorted view? (i.e. are two lists needed or can
> we
> stick to one?)
> 

Internally of course we'll always have to have 2 lists. I couldn't find
any examples of even root users needing the list to be in order by
address. At the same time, it feels like a less risky thing to do to
leave root users with the same thing they've always had and only muck
with non-root users.