Re: [RFC 4/5] user namespaces: allow killing tasks in your own or child userns

["Serge E. Hallyn" <serge@hallyn.com>]

Quoting Eric W. Biederman (ebiederm@xmission.com):
> > --- a/kernel/signal.c
> > +++ b/kernel/signal.c
> > @@ -659,11 +686,7 @@ static int check_kill_permission(int sig, struct siginfo *info,
> >  	cred = current_cred();
> >  	tcred = __task_cred(t);
> Nit pick  you don't need to compute cred and tcred here now.

Just to make sure I understand right: you mean wait until after the
same_thread_group() check to save calculation in that case, right?

> >  	if (!same_thread_group(current, t) &&
> > -	    (cred->euid ^ tcred->suid) &&
> > -	    (cred->euid ^ tcred->uid) &&
> > -	    (cred->uid  ^ tcred->suid) &&
> > -	    (cred->uid  ^ tcred->uid) &&
> > -	    !capable(CAP_KILL)) {
> > +	    !kill_ok_by_cred(t)) {
> >  		switch (sig) {
> >  		case SIGCONT:
> >  			sid = task_session(t);