linux-kernel - Re: [PATCH -v2] capabilites: allow the application of capability limits to usermode helpers

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Message-ID: <20110309194501.GA9362@albatros>
Date:	Wed, 9 Mar 2011 22:45:01 +0300
From:	Vasiliy Kulikov <segoon@...nwall.com>
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, dhowells@...hat.com,
	jmorris@...ei.org, serge.hallyn@...onical.com, morgan@...nel.org
Subject: Re: [PATCH -v2] capabilites: allow the application of capability
 limits to usermode helpers

Eric,

On Wed, Mar 09, 2011 at 14:33 -0500, Eric Paris wrote:
> someone complained that any user with
> cap_net_admin was able to load arbitrary kernel modules, even though the user
> didn't have cap_sys_module.  The reason is because the actual load is done by
> a usermode helper and those always have the full cap set.

AFAIU, your patch sets system-wide caps for _all_ usermode helpers,
right?  Then it does nothing with cap_net_admin's problem as it should
restrict caps of specific helpers spawned from specific networking code,
but not touching anything related to another helpers.

> sysctls which allow us to bound the permissions of usermode helpers.
> 
> /proc/sys/kernel/usermodehelper/bset
> /proc/sys/kernel/usermodehelper/inheritable
> 
> You must have CAP_SYS_MODULE to change these (changes are &= ONLY).
> When the kernel launches a usermodehelper it will do so with these as
> the bset and pI.

Thanks,

-- 
Vasiliy
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