linux-kernel - Re: [PATCH v3 08/10] x86: Add support for function granular KASLR

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Date:   Wed, 24 Jun 2020 00:11:21 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Kristen Carlson Accardi <kristen@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        Jonathan Corbet <corbet@....net>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, arjan@...ux.intel.com,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        rick.p.edgecombe@...el.com, Tony Luck <tony.luck@...el.com>,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 08/10] x86: Add support for function granular KASLR

On Tue, Jun 23, 2020 at 10:23:25AM -0700, Kristen Carlson Accardi wrote:
> This commit contains the changes required to re-layout the kernel text
> sections generated by -ffunction-sections shortly after decompression.
> Documentation of the feature is also added.
> [...]
> Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> Tested-by: Tony Luck <tony.luck@...el.com>

This looks good! I wonder about some way (in the future) to share the
sorting routines for kallsyms, exceptions, orc, etc. For now, though, I
think this is fine.

> [...]
> +	if (cmdline_find_option("fgkaslr", arg, sizeof(arg)) == 3 &&
> +	    !strncmp(arg, "off", 3)) {
> +		warn("FG_KASLR disabled on cmdline.");
> +		nofgkaslr = 1;
> +	}

I was recently reminded by Randy Lunlap to document my new boot params,
so I need to point out the same here. :) With a section added to
Documentation/admin-guide/kernel-parameters.txt
consider this:

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook