Messages in this thread | | | Date | Wed, 22 Jul 2015 15:03:42 +0300 | From | Konstantin Khlebnikov <> | Subject | Re: [PATCH v2] cgroup: net_cls: fix false-positive "suspicious RCU usage" |
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On 22.07.2015 14:56, Daniel Borkmann wrote: > On 07/22/2015 11:23 AM, Konstantin Khlebnikov wrote: >> In dev_queue_xmit() net_cls protected with rcu-bh. > ... >> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> >> --- >> net/core/netclassid_cgroup.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/net/core/netclassid_cgroup.c b/net/core/netclassid_cgroup.c >> index 1f2a126f4ffa..6441f47b1a8f 100644 >> --- a/net/core/netclassid_cgroup.c >> +++ b/net/core/netclassid_cgroup.c >> @@ -23,7 +23,8 @@ static inline struct cgroup_cls_state >> *css_cls_state(struct cgroup_subsys_state >> >> struct cgroup_cls_state *task_cls_state(struct task_struct *p) >> { >> - return css_cls_state(task_css(p, net_cls_cgrp_id)); >> + return css_cls_state(task_css_check(p, net_cls_cgrp_id, >> + rcu_read_lock_bh_held())); > > Did you also check that after your patch this doesn't trigger on ingress > either? There, this code path could be invoked under rcu_read_lock(). So, > perhaps you need to check for both.
I haven't seen warnings with this patch. rcu_read_lock_held() is checked inside rcu_dereference_check() inside task_css_check().
So, overall check expression is:
lockdep_is_held(&cgroup_mutex) || <- in task_css_set_check lockdep_is_held(&css_set_rwsem) || ((task)->flags & PF_EXITING) || rcu_read_lock_bh_held() || <- mine rcu_read_lock_held() <- in rcu_dereference_check
> >> } >> EXPORT_SYMBOL_GPL(task_cls_state);
-- Konstantin
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