netdev - Re: [patch 2/4] mISDN: add support for group membership check

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Message-Id: <20130920.121535.1653382964468102292.davem@davemloft.net>
Date:	Fri, 20 Sep 2013 12:15:35 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	jslaby@...e.cz
Cc:	ben@...adent.org.uk, akpm@...ux-foundation.org, jeffm@...e.com,
	netdev@...r.kernel.org, isdn4linux@...pen.de, isdn@...ux-pingi.de,
	sergei.shtylyov@...entembedded.com
Subject: Re: [patch 2/4] mISDN: add support for group membership check

From: Jiri Slaby <jslaby@...e.cz>
Date: Fri, 20 Sep 2013 18:14:28 +0200

> On 09/20/2013 05:56 PM, David Miller wrote:
>> From: Jiri Slaby <jslaby@...e.cz>
>> Date: Fri, 20 Sep 2013 15:44:33 +0200
>> 
>>> On 09/15/2013 01:28 AM, Ben Hutchings wrote:
>>>>> @@ -694,6 +699,10 @@ base_sock_ioctl(struct socket *sock, uns 
>>>>> case IMSETDEVNAME: { struct mISDN_devrename dn; +		if
>>>>> (!capable(CAP_SYS_ADMIN) && +				!gid_eq(misdn_permitted_gid,
>>>>> current_gid()) && +				!in_group_p(misdn_permitted_gid)) +
>>>>> return -EPERM; if (copy_from_user(&dn, (void __user *)arg, 
>>>>> sizeof(dn))) { err = -EFAULT;
>>>>
>>>> This seems to be the important bit: renaming of devices (if allowed
>>>> at all) ought to be limited to CAP_SYS_ADMIN or possibly
>>>> CAP_NET_ADMIN. But why should the group that is allowed to use
>>>> mISDN data sockets also be allowed to do this?
>>>
>>> This is based on an old patch we are dragging in SUSE since 2009:
>>> http://www.isdn4linux.de/pipermail/isdn4linux/2009-December/004493.html
>>> https://bugzilla.novell.com/show_bug.cgi?id=564423
>>>
>>> The whole point of the gid-based access was to still allow some user
>>> group to manipulate the device in an arbitrary way.
>>>
>>> So if everybody agrees I will just disallow rename to
>>> non-CAP_NET_ADMIN users and we are done?
>> 
>> No we are not done, sorry.
>> 
>> Having a device specific module parameter for this is wrong on several
>> fundamental levels.
> 
> What I'm suggesting is just to put a !capable(CAP_NET_ADMIN) test into
> the rename path and nothing more.

And I'm saying that regardless of such a change, the patch itself
is fundamentally implemented incorrectly and not acceptable for
upstream inclusion until the interface for configuration is changed.
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