Re: [PATCH v1 1/1] waitid: Add support for waiting for the current process group

[Christian Brauner]

On Wed, Aug 14, 2019 at 02:50:12PM +0200, Oleg Nesterov wrote:
> On 08/14, Christian Brauner wrote:
> >
> > On Wed, Aug 14, 2019 at 02:29:10PM +0200, Oleg Nesterov wrote:
> > > On 08/14, christian.brauner@xxxxxxxxxx wrote:
> > > >
> > > >  	case P_PGID:
> > > >  		type = PIDTYPE_PGID;
> > > > -		if (upid <= 0)
> > > > +		if (upid < 0)
> > > >  			return -EINVAL;
> > > > +
> > > > +		if (upid == 0)
> > > > +			pid = get_pid(task_pgrp(current));
> > >
> > > this needs rcu lock or tasklist_lock, this can race with another thread
> > > doing sys_setpgid/setsid (see change_pid(PIDTYPE_PGID)).
> >
> > Oh, I naively assumed task_pgrp() would take an rcu lock...
> 
> but it would not help ;)

Yeah, it doesn't do a get. :)