linux-kernel - Re: [PATCH 4/9] allow killing tasks in your own or child userns

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Message-ID: <20110224004818.GA11822@mail.hallyn.com>
Date:	Thu, 24 Feb 2011 00:48:18 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	LSM <linux-security-module@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	Kees Cook <kees.cook@...onical.com>,
	containers@...ts.linux-foundation.org,
	kernel list <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Michael Kerrisk <mtk.manpages@...il.com>, xemul@...allels.com,
	dhowells@...hat.com
Subject: Re: [PATCH 4/9] allow killing tasks in your own or child userns

Quoting Andrew Morton (akpm@...ux-foundation.org):
> On Thu, 17 Feb 2011 15:03:25 +0000
> "Serge E. Hallyn" <serge@...lyn.com> wrote:
> 
> >  /*
> > + * called with RCU read lock from check_kill_permission()
> > + */
> > +static inline int kill_ok_by_cred(struct task_struct *t)
> > +{
> > +	const struct cred *cred = current_cred();
> > +	const struct cred *tcred = __task_cred(t);
> > +
> > +	if (cred->user->user_ns == tcred->user->user_ns &&
> > +	    (cred->euid == tcred->suid ||
> > +	     cred->euid == tcred->uid ||
> > +	     cred->uid  == tcred->suid ||
> > +	     cred->uid  == tcred->uid))
> > +		return 1;
> > +
> > +	if (ns_capable(tcred->user->user_ns, CAP_KILL))
> > +		return 1;
> > +
> > +	return 0;
> > +}
> 
> The compiler will inline this for us.

Is that simply true with everything (worth inlining) nowadays, or is
there a particular implicit hint to the compiler that'll make that
happen?

Not that I guess it's even particularly important in this case.

From: Serge E. Hallyn <serge.hallyn@...onical.com>
Date: Thu, 24 Feb 2011 00:26:02 +0000
Subject: [PATCH 1/2] userns: let compiler inline kill_ok_by_cred (per akpm)

Signed-off-by: Serge E. Hallyn <serge.hallyn@...onical.com>
---
 kernel/signal.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index ffe4bdf..12702b4 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -638,7 +638,7 @@ static inline bool si_fromuser(const struct siginfo *info)
 /*
  * called with RCU read lock from check_kill_permission()
  */
-static inline int kill_ok_by_cred(struct task_struct *t)
+static int kill_ok_by_cred(struct task_struct *t)
 {
 	const struct cred *cred = current_cred();
 	const struct cred *tcred = __task_cred(t);
-- 
1.7.0.4

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