linux-kernel - Re: [RFC] export module parameters even the permission is zero

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Date:	Tue, 13 Jan 2015 21:46:25 -0800
From:	Kees Cook <keescook@...omium.org>
To:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
Cc:	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"jani.nikula@...el.com" <jani.nikula@...el.com>,
	"hch@...radead.org" <hch@...radead.org>,
	"hare@...e.de" <hare@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] export module parameters even the permission is zero

On Tue, Jan 13, 2015 at 6:16 PM, Wang, Yalin <Yalin.Wang@...ymobile.com> wrote:
> This patch make sure to export module parameters even the permission
> is zero, this is useful for some platforms like Android,
> the init process can change the parameter mode/owner by
> chmod/chown during bootup
>
> Signed-off-by: Yalin Wang <yalin.wang@...ymobile.com>

NAK. No sorry, these parameters are explicitly being removed from
sysfs by the various things that use perm==0. This would potentially
expose sensitive values to sysfs. If a value should be exposed, the
perm argument on the specific thing should be changed.

-Kees

> ---
>  kernel/params.c | 6 ------
>  1 file changed, 6 deletions(-)
>
> diff --git a/kernel/params.c b/kernel/params.c
> index bd65d136..aa80c04 100644
> --- a/kernel/params.c
> +++ b/kernel/params.c
> @@ -607,9 +607,6 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
>         struct attribute **new_attrs;
>         unsigned int i;
>
> -       /* We don't bother calling this with invisible parameters. */
> -       BUG_ON(!kp->perm);
> -
>         if (!mk->mp) {
>                 /* First allocation. */
>                 mk->mp = kzalloc(sizeof(*mk->mp), GFP_KERNEL);
> @@ -812,9 +809,6 @@ static void __init param_sysfs_builtin(void)
>         for (kp = __start___param; kp < __stop___param; kp++) {
>                 char *dot;
>
> -               if (kp->perm == 0)
> -                       continue;
> -
>                 dot = strchr(kp->name, '.');
>                 if (!dot) {
>                         /* This happens for core_param() */
> --
> 2.1.3



-- 
Kees Cook
Chrome OS Security
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