linux-kernel - Re: [PATCH] retpoline/module: Taint kernel for missing retpoline in module

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Date:   Sat, 13 Jan 2018 15:12:09 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     tglx@...utronix.de, dwmw@...zon.co.uk,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        arjan.van.de.ven@...el.com, peterz@...radead.org,
        Andi Kleen <ak@...ux.intel.com>, jeyu@...nel.org
Subject: Re: [PATCH] retpoline/module: Taint kernel for missing retpoline in
 module

On Fri, Jan 12, 2018 at 09:55:07AM -0800, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> There's a risk that a kernel that has full retpoline mitigations
> becomes vulnerable when a module gets loaded that hasn't been
> compiled with the right compiler or the right option.
> 
> We cannot fix it, but should at least warn the user when that
> happens.
> 
> Add a flag to each module if it has been compiled with RETPOLINE
> 
> When the a module hasn't been compiled with a retpoline
> aware compiler, print a warning and set a taint flag.

Isn't that caught by the "build with a different compiler/version" check
that we have?  Or used to have?  If not, can't we just make it into that
type of check to catch this type of problem no matter what type of
feature/option it is trying to catch?

thanks,

greg k-h