Messages in this thread | | | Subject | Re: [PATCH RFC] sched: Revert delayed_put_task_struct() and fix use after free | From | Kirill Tkhai <> | Date | Thu, 16 Oct 2014 14:04:53 +0400 |
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В Чт, 16/10/2014 в 13:51 +0400, Kirill Tkhai пишет: > В Чт, 16/10/2014 в 13:50 +0400, Kirill Tkhai пишет: > > В Чт, 16/10/2014 в 11:43 +0200, Peter Zijlstra пишет: > > > On Thu, Oct 16, 2014 at 12:16:44PM +0400, Kirill Tkhai wrote: > > > > В Чт, 16/10/2014 в 09:59 +0200, Peter Zijlstra пишет: > > > > > On Thu, Oct 16, 2014 at 01:46:07AM +0400, Kirill Tkhai wrote: > > > > > > > --- x/kernel/sched/fair.c > > > > > > > +++ x/kernel/sched/fair.c > > > > > > > @@ -1165,7 +1165,7 @@ static void task_numa_compare(struct tas > > > > > > > > > > > > > > rcu_read_lock(); > > > > > > > cur = ACCESS_ONCE(dst_rq->curr); > > > > > > > - if (cur->pid == 0) /* idle */ > > > > > > > + if (is_idle_task(cur) || (curr->flags & PF_EXITING)) > > > > > > > cur = NULL; > > > > > > > > > > > > > > /* > > > > > > > > > > > > > > > > > > > Looks like, we have to use the same fix for task_numa_group(). > > > > > > > > > > Don't think so, task_numa_group() is only called from task_numa_fault() > > > > > which is on 'current' and neither idle and PF_EXITING should be > > > > > faulting. > > > > > > > > Isn't task_numa_group() fully preemptible? > > > > > > Not seeing how that is relevant. > > > > > > > It seems cpu_rq(cpu)->curr is not always equal to p. > > > > > > It should be afaict: > > > > > > task_numa_fault() > > > p = current; > > > > > > task_numa_group(p, ..); > > > > > > And like said, idle tasks and PF_EXITING task should never get (numa) > > > faults for they should never be touching userspace. > > > > I mean p can be moved to other cpu. > > > > tsk = ACCESS_ONCE(cpu_rq(cpu)->curr); > > > > tsk is not p, (i.e current) here. > > Maybe I undestand wrong and preemption is disabled in memory fault?
Ah, I found pagefault_disable(). No questions.
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