linux-kernel - Re: [PATCH] pidns: Limit kill -1 and cap_set

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Message-Id: <1193673738.24087.176.camel@localhost>
Date:	Mon, 29 Oct 2007 09:02:18 -0700
From:	Dave Hansen <haveblue@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Linux Containers <containers@...ts.osdl.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...sign.ru>,
	Pavel Emelyanov <xemul@...nvz.org>,
	"Sukadev Bhattiprolu [imap]" <sukadev@...ibm.com>
Subject: Re: [PATCH] pidns: Limit kill -1 and cap_set_all

On Fri, 2007-10-26 at 14:37 -0600, Eric W. Biederman wrote:
> 
> +static int pid_in_pid_ns(struct pid *pid, struct pid_namespace *ns)
> +{
> +       return pid && (ns->level <= pid->level) &&
> +               pid->numbers[ns->level].ns == ns;
> +}

Could we blow this out a little bit?  (I think the blown-out version
lends itself to being better commented, and easier to read.)  Also, can
we think of any better name for this?  It seems a bit funky that:

	pid_in_pid_ns(mypid, &init_pid_ns);

would _ever_ return 0.  So, it isn't truly a test for belonging *in* a
namespace, but having that namespace be the lowest level one.  I think
Suka toyed with calling it an "active" or "primary" pid namespace.  That
differentiated mere membership in a pid namespace from the one that
actually molds that pid's view of the world.

static int pid_in_pid_ns(struct pid *pid, struct pid_namespace *ns)
{
	if (!pid)
		return 0;
	if (ns->level > pid->level)
		return 0;
	if (pid->numbers[ns->level].ns != ns)
		return 0;
	return 1;
}

-- Dave

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