linux-kernel - Re: [PATCH v3] retpoline: Add retpoline tag to VERMAGIC

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Date:   Tue, 16 Jan 2018 22:24:53 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andi Kleen <andi@...stfloor.org>
cc:     torvalds@...ux-foundation.org, dwmw@...zon.co.uk,
        linux-kernel@...r.kernel.org, gregkh@...ux-foundation.org,
        arjan.van.de.ven@...el.com, jeyu@...nel.org, rusty@...tcorp.com.au,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v3] retpoline: Add retpoline tag to VERMAGIC

On Tue, 16 Jan 2018, Andi Kleen wrote:

> From: Andi Kleen <ak@...ux.intel.com>
> 
> Add a marker for retpoline to the module VERMAGIC. This catches
> the case when a non RETPOLINE compiled module gets loaded into
> a retpoline kernel, making it insecure.
> 
> It doesn't handle the case when retpoline has been runtime disabled.
> Even in this case the match of the retcompile status will be enforced.
> This implies that even with retpoline run time disabled all modules
> loaded need to be recompiled.
> 
> This supersedes an earlier patch that did the same checking using
> a new module tag (so it's really a v3)
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>

Acked-by: Thomas Gleixner <tglx@...utronix.de>

> ---
>  include/linux/vermagic.h | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h
> index bae807eb2933..853291714ae0 100644
> --- a/include/linux/vermagic.h
> +++ b/include/linux/vermagic.h
> @@ -31,11 +31,17 @@
>  #else
>  #define MODULE_RANDSTRUCT_PLUGIN
>  #endif
> +#ifdef RETPOLINE
> +#define MODULE_VERMAGIC_RETPOLINE "retpoline "
> +#else
> +#define MODULE_VERMAGIC_RETPOLINE ""
> +#endif
>  
>  #define VERMAGIC_STRING 						\
>  	UTS_RELEASE " "							\
>  	MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT 			\
>  	MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS	\
>  	MODULE_ARCH_VERMAGIC						\
> -	MODULE_RANDSTRUCT_PLUGIN
> +	MODULE_RANDSTRUCT_PLUGIN					\
> +	MODULE_VERMAGIC_RETPOLINE
>  
> -- 
> 2.14.3
> 
>