Re: hit a KASan bug related to Perf during stress test

Oleg Nesterov
2016-10-24T12:04:07Z

On 10/24, Peter Zijlstra wrote:
>
> On Mon, Oct 24, 2016 at 01:15:27PM +0200, Oleg Nesterov wrote:
> >
> > --- x/kernel/events/core.c
> > +++ x/kernel/events/core.c
> > @@ -1257,7 +1257,7 @@ static u32 perf_event_pid(struct perf_ev
> > if (event->parent)
> > event = event->parent;
> >
> > - return task_tgid_nr_ns(p, event->ns);
> > + return pid_alive(p) ? task_tgid_nr_ns(p, event->ns) : 0;
> > }
>
> Hurm.. should we not push this into task_tgid_nr_ns() ? I mean, now the
> user needs to be aware of this dinky detail.

Perhaps. Or into task_tgid(). Or even the patch below, __task_pid_nr_ns()
is always safe. This certainly needs some cleanups.

Oleg.

--- x/include/linux/pid.h
+++ x/include/linux/pid.h
@@ -8,7 +8,8 @@ enum pid_type
PIDTYPE_PID,
PIDTYPE_PGID,
PIDTYPE_SID,
- PIDTYPE_MAX
+ PIDTYPE_MAX,
+ PIDTYPE_TGID /* do not use */
};

/*
--- x/kernel/pid.c
+++ x/kernel/pid.c
@@ -538,7 +538,7 @@ EXPORT_SYMBOL(__task_pid_nr_ns);

pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
{
- return pid_nr_ns(task_tgid(tsk), ns);
+ return __task_pid_nr_ns(tsk, PIDTYPE_TGID, ns);
}
EXPORT_SYMBOL(task_tgid_nr_ns);