linux-kernel - Re: [PATCH] capabilities/syslog: open code cap

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Message-ID: <20101118200838.GH13854@outflux.net>
Date:	Thu, 18 Nov 2010 12:08:38 -0800
From:	Kees Cook <kees.cook@...onical.com>
To:	"Serge E. Hallyn" <serge.hallyn@...onical.com>
Cc:	Eric Paris <eparis@...hat.com>, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	torvalds@...ux-foundation.org, joe@...ches.com,
	drosenberg@...curity.com, mingo@...e.hu, eugeneteo@...nel.org,
	akpm@...ux-foundation.org, jmorris@...ei.org, morgan@...nel.org,
	casey@...aufler-ca.com
Subject: Re: [PATCH] capabilities/syslog: open code cap_syslog logic to fix
 build failure

Hi Serge,

On Thu, Nov 18, 2010 at 08:26:24AM -0600, Serge E. Hallyn wrote:
> Quoting Eric Paris (eparis@...hat.com):
> > @@ -274,7 +274,20 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
> >  	char c;
> >  	int error = 0;
> >  
> > -	error = security_syslog(type, from_file);
> > +	/*
> > +	 * If this is from /proc/kmsg we only do the capabilities checks
> > +	 * at open time.
> > +	 */
> > +	if (type == SYSLOG_ACTION_OPEN || !from_file) {
> > +		if (dmesg_restrict && !capable(CAP_SYS_ADMIN))
> 
> Any chance we could introduce a new capability for this?

Wasn't there talk of creating CAP_SYSLOG or something? Right now most
sysklogd implementations are just starting life as root, so making this
change now shouldn't break anyone.

-Kees

-- 
Kees Cook
Ubuntu Security Team
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