Re: [Bug #15615] NULL pointer deref in task_is_waking

Liang Li
2010-04-08T08:21:45Z

On Thu, Apr 08, 2010 at 03:50:03PM +0800, Yong Zhang wrote:
> On Thu, Apr 08, 2010 at 03:16:17PM +0800, Liang Li wrote:
> > On Wed, Apr 07, 2010 at 11:13:48PM +0200, Rafael J. Wysocki wrote:
> > > This message has been generated automatically as a part of a summary report
> > > of recent regressions.
> > >
> > > The following bug entry is on the current list of known regressions
> > > from 2.6.33. Please verify if it still should be listed and let the tracking team
> > > know (either way).
> >
> > The bug still there. I just met it. And seems its quite simple to get it
> > fixed.
> >
> > diff --git a/kernel/sched.c b/kernel/sched.c
> > index a3dff1f..2df1a76 100644
> > --- a/kernel/sched.c
> > +++ b/kernel/sched.c
> > @@ -913,7 +913,7 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
> > */
> > static inline int task_is_waking(struct task_struct *p)
> > {
> > - return unlikely((p->state == TASK_WAKING) && !(p->flags & PF_STARTING));
> > + return unlikely(p && (p->state == TASK_WAKING) && !(p->flags & PF_STARTING));
> > }

Seems what I saw was different from this bug. So it is clear
that this one line change does not relate to this bug. Sorry
for confusion.

>
> Oh, NO. This is wrong. It will introduce other bugs.
> The right direction is showed in the bug entry.

Thanks,
-Liang Li
>
> Thanks,
> Yong
>
> >
> > /*
> >
> > But seems commitid 0017d735092844118bef006696a750a0e4ef6ebd in tip tree
> > also touched task_is_waking. So the patch for tip tree should be:
> >
> > diff --git a/kernel/sched.c b/kernel/sched.c
> > index 3acf694..d259641 100644
> > --- a/kernel/sched.c
> > +++ b/kernel/sched.c
> > @@ -920,7 +920,7 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
> > */
> > static inline int task_is_waking(struct task_struct *p)
> > {
> > - return unlikely(p->state == TASK_WAKING);
> > + return unlikely(p && p->state == TASK_WAKING);
> > }
> >
> > /*
> >
> > Regards,
> > -Liang Li
> >
> > >
> > >
> > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=15615
> > > Subject : NULL pointer deref in task_is_waking
> > > Submitter : Amit Shah <shahamit@gmail.com>
> > > Date : 2010-03-23 04:04 (16 days old)
> > >
> > >
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > > Please read the FAQ at http://www.tux.org/lkml/
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/