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

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Message-ID: <CAG48ez2SucOZORUhHNxt-9juzqcWjTZRD9E_PhP51LpH1UqeLg@mail.gmail.com>
Date:   Thu, 6 Feb 2020 20:27:45 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Kristen Carlson Accardi <kristen@...ux.intel.com>
Cc:     Kees Cook <keescook@...omium.org>,
        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 Thu, Feb 6, 2020 at 6:51 PM Kristen Carlson Accardi
<kristen@...ux.intel.com> wrote:
> On Thu, 2020-02-06 at 04:32 -0800, Kees Cook wrote:
> > In the past, making kallsyms entirely unreadable seemed to break
> > weird
> > stuff in userspace. How about having an alternative view that just
> > contains a alphanumeric sort of the symbol names (and they will
> > continue
> > to have zeroed addresses for unprivileged users)?
> >
> > Or perhaps we wait to hear about this causing a problem, and deal
> > with
> > it then? :)
> >
>
> Yeah - I don't know what people want here. Clearly, we can't leave
> kallsyms the way it is. Removing it entirely is a pretty fast way to
> figure out how people use it though :).

FYI, a pretty decent way to see how people are using an API is
codesearch.debian.net, which searches through the source code of all
the packages debian ships:

https://codesearch.debian.net/search?q=%2Fproc%2Fkallsyms&literal=1