Messages in this thread | | | Date | Thu, 3 Jun 2010 16:48:10 +0200 | From | Oleg Nesterov <> | Subject | Re: [RFC] [PATCH 2/2] cgroups: make procs file writable |
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On 06/03, Ben Blum wrote: > > On Wed, Jun 02, 2010 at 10:58:55PM +0200, Oleg Nesterov wrote: > > Hmm. The usage of ->thread_group in ->can_attach() methods doesn't > > look safe to me... but currently bool threadgroup is always false. > > I recall putting a rcu_read_lock() around that part and being assured > that made it safe. But I don't remember the details. Maybe taking > tasklist_lock is necessary?
rcu_read_lock() is not enough, see another email I sent.
Once again.
rcu_read_lock() list_for_each_rcu(tsk->thread_group)
assumes that at least tsk->thread_group->next can't point to nowhere, this is not true. This memory can go away _before_ we take rcu lock.
Oleg.
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