linux-kernel - Re: [PATCH v4 1/2] Provide in-kernel headers for making it easy to extend the kernel

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Message-ID: <20190309071648.GE3882@kroah.com>
Date:   Sat, 9 Mar 2019 08:16:48 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexei Starovoitov <ast@...nel.org>,
        atish patra <atishp04@...il.com>,
        Daniel Colascione <dancol@...gle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Guenter Roeck <groeck@...omium.org>,
        Jonathan Corbet <corbet@....net>,
        Karim Yaghmour <karim.yaghmour@...rsys.com>,
        Kees Cook <keescook@...omium.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        linux-trace-devel@...r.kernel.org,
        Manoj Rao <linux@...ojrajarao.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Qais Yousef <qais.yousef@....com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Shuah Khan <shuah@...nel.org>, Yonghong Song <yhs@...com>
Subject: Re: [PATCH v4 1/2] Provide in-kernel headers for making it easy to
 extend the kernel

On Fri, Mar 08, 2019 at 06:59:23PM +0100, Geert Uytterhoeven wrote:
> Hi Greg,
> 
> On Fri, Mar 8, 2019 at 6:05 PM Greg KH <gregkh@...uxfoundation.org> wrote:
> > On Fri, Mar 08, 2019 at 05:42:32AM -0800, Joel Fernandes wrote:
> > > On Fri, Mar 8, 2019, 3:53 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > > > It is just so much easier to use tar + xz at build time, and leave the
> > > > > decompression task to the user. After decompression, the files will live on
> > > > > the disk and the page-cache mechanism will free memory when/if the files fall
> > > > > off the LRUs.
> > > >
> > > > I'm also considering how generic and extensible the solution is.
> > > > What if people need other build artifacts in the future (e.g. signing key to
> > > > load signed modules)?
> > >
> > > That sounds like it could be useful. I don't see any reason off the
> > > top why that would not be possible to add to the list of archived
> > > files in the future. The patch allows populating the list of files
> > > from Kbuild using ikh_file_list variable.
> >
> > Um, no, you don't want the signing key in the kernel itself, as that
> > totally defeats the purpose of the signing key :)
> 
> In a loadable module?
> He who has the module, can build and sign more modules.

Again, that's pretty foolish.

Signing keys should be kept secure, or better yet, just deleted entirely
after creating and signing with them.  That's what I do for my kernels
and I'm pretty sure that some distros also do this.  That way there's no
chance that someone else can sign a module and have it loaded without
detection, which is what signing is supposed to prevent from happening.

thanks,

greg k-h