linux-kernel - Re: [PATCH 1/2] module: export module signature enforcement status

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Message-Id: <1508763415.3639.91.camel@linux.vnet.ibm.com>
Date:   Mon, 23 Oct 2017 08:56:55 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     "Bruno E. O. Meneguele" <brdeoliv@...hat.com>,
        linux-kernel@...r.kernel.org
Cc:     linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, serge@...lyn.com,
        james.l.morris@...cle.com, dmitry.kasatkin@...il.com,
        rusty@...tcorp.com.au, jeyu@...nel.org
Subject: Re: [PATCH 1/2] module: export module signature enforcement status

On Fri, 2017-10-20 at 17:19 -0200, Bruno E. O. Meneguele wrote:
> A static variable sig_enforce is used as status var to indicate the real
> value of CONFIG_MODULE_SIG_FORCE, once this one is set the var will hold
> true, but if the CONFIG is not set the status var will hold whatever
> value is present in the module.sig_enforce kernel cmdline param: true
> when =1 and false when =0 or not present.
> 
> Considering this cmdline param take place over the CONFIG value when
> it's not set, other places in the kernel could missbehave since they

^misbehave

> would have only the CONFIG_MODULE_SIG_FORCE value to rely on. Exporting
> this status var allows the kernel to rely in the effective value of
> module signature enforcement, being it from CONFIG value or cmdline
> param.

Thanks!  There's a minor checkpatch warning below.

> Signed-off-by: Bruno E. O. Meneguele <brdeoliv@...hat.com>
> ---
>  include/linux/module.h | 2 ++
>  kernel/module.c        | 8 ++++++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/include/linux/module.h b/include/linux/module.h
> index fe5aa3736707..ddfe17e3a85c 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -806,4 +806,6 @@ static inline bool module_sig_ok(struct module *module)
>  }
>  #endif	/* CONFIG_MODULE_SIG */
> 
> +bool is_module_sig_enforced(void);
> +
>  #endif /* _LINUX_MODULE_H */
> diff --git a/kernel/module.c b/kernel/module.c
> index de66ec825992..b93c7ff44066 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -278,6 +278,14 @@ static bool sig_enforce = IS_ENABLED(CONFIG_MODULE_SIG_FORCE);
>  module_param(sig_enforce, bool_enable_only, 0644);
>  #endif /* !CONFIG_MODULE_SIG_FORCE */
> 
> +/* Export sig_enforce kernel cmdline parameter to allow other subsystems rely
> + * on that instead of directly to CONFIG_MODULE_SIG_FORCE config. */

Checkpatch complains.  Please use the normal format:
/*
 *
 */

> +bool is_module_sig_enforced(void)
> +{
> +	return sig_enforce;
> +}
> +EXPORT_SYMBOL(is_module_sig_enforced);
> +
>  /* Block module loading/unloading? */
>  int modules_disabled = 0;
>  core_param(nomodule, modules_disabled, bint, 0);