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SubjectRe: [PATCH] cgroup: missing rcu read lock around task_css_set
On 2014/3/5 3:47, Tejun Heo wrote:
> On Tue, Mar 04, 2014 at 12:20:45PM -0500, Sasha Levin wrote:
>>> Hrm... there is a PF_EXITING check there already:
>>>
>>> #define task_css_set_check(task, __c) \
>>> rcu_dereference_check((task)->cgroups, \
>>> lockdep_is_held(&cgroup_mutex) || \
>>> lockdep_is_held(&css_set_rwsem) || \
>>> ((task)->flags & PF_EXITING) || (__c))
>>>
>>> I see it's not happening on Linus's master so I'll run a bisection to figure out what broke it.
>>
>> Hi Tejun,
>>
>> It bisects down to your patch: "cgroup: drop task_lock() protection
>> around task->cgroups". I'll look into it later unless it's obvious
>> to you.
>
> Hmmm... maybe I'm confused and PF_EXITING is not set there and
> task_lock was what held off the lockdep warning. Confused....
>

Because this cgroup_exit() is called in a failure path in copy_process().



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