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Re: [PATCH 1/3] module: Invalidate signatures on force-loaded modules

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Ben Hutchings <ben@decadent.org.uk> writes:
> Signing a module should only make it trusted by the specific kernel it
> was built for, not anything else.  Loading a signed module meant for a
> kernel with a different ABI could have interesting effects.
> Therefore, treat all signatures as invalid when a module is
> force-loaded.
>
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> Cc: stable@vger.kernel.org
> ---
>  kernel/module.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 66426f743c29..649b1827ed15 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2599,13 +2599,18 @@ static inline void kmemleak_load_module(const struct module *mod,
>  #endif
>  
>  #ifdef CONFIG_MODULE_SIG
> -static int module_sig_check(struct load_info *info)
> +static int module_sig_check(struct load_info *info, int flags)
>  {
>  	int err = -ENOKEY;
>  	const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
>  	const void *mod = info->hdr;
>  
> -	if (info->len > markerlen &&
> +	/*
> +	 * Require flags == 0, as a module with version information
> +	 * removed is no longer the module that was signed
> +	 */
> +	if (flags == 0 &&

This check is a bit lazy.  We could have other flags in future,
so this should really be !(flags &
(MODULE_INIT_IGNORE_MODVERSIONS|MODULE_INIT_IGNORE_VERMAGIC) right?

Cheers,
Rusty.

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[PATCH 0/3] Module signing and version info Ben Hutchings <ben@decadent.org.uk> - 2016-04-23 20:50 +0200
  [PATCH 3/3] module: Disable MODULE_FORCE_LOAD when MODULE_SIG_FORCE  is enabled Ben Hutchings <ben@decadent.org.uk> - 2016-04-23 20:50 +0200
  [PATCH 2/3] Documentation/module-signing.txt: Note need for version  info if reusing a key Ben Hutchings <ben@decadent.org.uk> - 2016-04-23 20:50 +0200
  [PATCH 1/3] module: Invalidate signatures on force-loaded modules Ben Hutchings <ben@decadent.org.uk> - 2016-04-23 20:50 +0200
    Re: [PATCH 1/3] module: Invalidate signatures on force-loaded modules Rusty Russell <rusty@rustcorp.com.au> - 2016-04-26 22:40 +0200
      Re: [PATCH 1/3] module: Invalidate signatures on force-loaded  modules Ben Hutchings <ben@decadent.org.uk> - 2016-04-26 23:10 +0200
        Re: [PATCH 1/3] module: Invalidate signatures on force-loaded modules Rusty Russell <rusty@rustcorp.com.au> - 2016-04-28 02:30 +0200

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