linux-kernel - Re: [patch 28/28] posix clocks: Introduce dynamic clocks

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Date:	Thu, 3 Mar 2011 18:07:59 +0100
From:	torbenh <torbenh@....de>
To:	Richard Cochran <richardcochran@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	John Stultz <john.stultz@...aro.org>,
	Richard Cochran <richard.cochran@...cron.at>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [patch 28/28] posix clocks: Introduce dynamic clocks

On Thu, Mar 03, 2011 at 05:01:14PM +0100, Richard Cochran wrote:
> On Thu, Mar 03, 2011 at 03:50:08PM +0100, torbenh wrote:
> > On Tue, Feb 01, 2011 at 01:52:35PM -0000, Thomas Gleixner wrote:
> > > +static int pc_clock_adjtime(clockid_t id, struct timex *tx)
> > > +{
> > > +	struct posix_clock_desc cd;
> > > +	int err;
> > > +
> > > +	err = get_clock_desc(id, &cd);
> > > +	if (err)
> > > +		return err;
> > 
> > there is no permission check here.
> > if i get the clock fd in READ mode, i can still adjtime.
> > same for settime.
> 
> You are right, but I think the check should be for the capability
> instead. Checking the file mode for RDWR seems a bit pedantic to me.

i dont see, why an fd based clock, which already has associated permissions,
should check against the capability.
why should the ptpd be running as root ?
changing the permissions of /dev/ptp0 to allow ptpd to set the
clock should be enough. 

> 
> For the normal system timer, clock_settime calls security_settime, but
> adjtimex calls capable(CAP_SYS_TIME) directly. Perhaps adjtimex should
> also use the security call, too.

probably yes.

> 
> Thanks,
> 
> Richard
> 
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-- 
torben Hohn
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