linux-kernel - Re: CAP_SYSLOG, 2.6.38 and user space

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Message-ID: <alpine.DEB.2.00.1102042301420.8162@asgard.lang.hm>
Date:	Fri, 4 Feb 2011 23:05:55 -0800 (PST)
From:	david@...g.hm
To:	"Serge E. Hallyn" <serge@...lyn.com>
cc:	Gergely Nagy <algernon@...abit.hu>,
	James Morris <jmorris@...ei.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: CAP_SYSLOG, 2.6.38 and user space

On Fri, 4 Feb 2011, Serge E. Hallyn wrote:

> Quoting Gergely Nagy (algernon@...abit.hu):
>> On Fri, 2011-02-04 at 16:05 +0000, Serge E. Hallyn wrote:
>>> Quoting Serge E. Hallyn (serge@...lyn.com):
>>>>> From 2d7408541dd3a6e19a4265b028233789be6a40f4 Mon Sep 17 00:00:00 2001
>>>> From: Serge Hallyn <serge@....(none)>
>>>>
>>>> At 2.6.39 or 2.6.40, let's add a sysctl which defaults to 0.  When
>>>> 0, refuse if cap_sys_admin, if 1, then allow.  This will allow
>>>> users to acknowledge (permanently, if they must, using /etc/sysctl.conf)
>>>> that they've seen the syslog message about cap_sys_admin being
>>>> deprecated for syslog.
>>>>
>>>> Signed-off-by: Serge Hallyn <serge@...lyn.com>
> -			goto warn; /* switch to return -EPERM after 2.6.39 */
> +		     !capable(CAP_SYSLOG)) {
> +			/* remove after 2.6.39 */
> +			if (capable(CAP_SYS_ADMIN))
> +				WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
> +				  "but no CAP_SYSLOG (deprecated).\n");
> +			else
> +				return -EPERM;
> +		}
> 	}

why does this need to be removed after 2.6.39?

whenever you go to remove it you will break userspace, what's the benifit 
of breaking userspace?

I can understand that it's better to have a syslog daemon with CAP_SYSLOG 
instead of CAP_SYS_ADMIN, but does "it would be better to have userspace 
changed" really translate into "it's so important to have userspace 
changed that we need to break any userspace that hasn't changed"?

I really don't think so.

David Lang
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