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

Liang Li
2010-04-08T07:18:14Z

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));
}

/*

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/