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Groups > linux.kernel > #1359198

Re: [BUG] sched: leaf_cfs_rq_list use after free

From Tejun Heo <tj@kernel.org>
Newsgroups linux.kernel
Subject Re: [BUG] sched: leaf_cfs_rq_list use after free
Date 2016-03-16 18:50 +0100
Message-ID <rdnK2-3Gs-13@gated-at.bofh.it> (permalink)
References (2 earlier) <rcztU-3yx-27@gated-at.bofh.it> <rdkCu-1FX-3@gated-at.bofh.it> <rdlyy-2jP-15@gated-at.bofh.it> <rdmXE-36t-3@gated-at.bofh.it> <rdn7l-3qk-25@gated-at.bofh.it>
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On Wed, Mar 16, 2016 at 06:04:56PM +0100, Peter Zijlstra wrote:
> > Hmmm... I don't think it'd be safe to merge the two ops.  Nothing
> > guarantees that the RCU callback of cpu controller is called after the
> > cgroup core one and cgroup core one would do use-after-free.  Just
> > changing offline to released should do.
> 
> I'm confused, the code looks like:
> 
> static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
> {
> 	struct task_group *tg = css_tg(css);
> 
> 	sched_offline_group(tg);
> }
> 
> static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
> {
> 	struct task_group *tg = css_tg(css);
> 
> 	/*
> 	 * Relies on the RCU grace period between css_release() and this.
> 	 */
> 	sched_free_group(tg);
> }

Oops, misread the two functions swapping positions as getting merged.
Yes, that is correct.  Sorry about the confusion.  Please feel free to
add

 Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

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Thread

Re: [BUG] sched: leaf_cfs_rq_list use after free Kazuki Yamaguchi <k@rhe.jp> - 2016-03-12 11:00 +0100
  Re: [BUG] sched: leaf_cfs_rq_list use after free Peter Zijlstra <peterz@infradead.org> - 2016-03-12 15:00 +0100
  Re: [BUG] sched: leaf_cfs_rq_list use after free Peter Zijlstra <peterz@infradead.org> - 2016-03-14 12:30 +0100
    Re: [BUG] sched: leaf_cfs_rq_list use after free Peter Zijlstra <peterz@infradead.org> - 2016-03-14 13:10 +0100
      Re: [BUG] sched: leaf_cfs_rq_list use after free Tejun Heo <tj@kernel.org> - 2016-03-16 15:30 +0100
        Re: [BUG] sched: leaf_cfs_rq_list use after free Tejun Heo <tj@kernel.org> - 2016-03-16 15:50 +0100
        Re: [BUG] sched: leaf_cfs_rq_list use after free Peter Zijlstra <peterz@infradead.org> - 2016-03-16 16:30 +0100
          Re: [BUG] sched: leaf_cfs_rq_list use after free Tejun Heo <tj@kernel.org> - 2016-03-16 18:00 +0100
            Re: [BUG] sched: leaf_cfs_rq_list use after free Peter Zijlstra <peterz@infradead.org> - 2016-03-16 18:10 +0100
              Re: [BUG] sched: leaf_cfs_rq_list use after free Tejun Heo <tj@kernel.org> - 2016-03-16 18:50 +0100
          Re: [BUG] sched: leaf_cfs_rq_list use after free Niklas Cassel <niklas.cassel@axis.com> - 2016-03-17 09:30 +0100

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