[Patch net 06/13] cls_flow: use tcf_exts_get_net() before call_rcu()

[Cong Wang]

Hold netns refcnt before call_rcu() and release it after
the tcf_exts_destroy() is done.

Note, on ->destroy() path we have to respect the return value
of tcf_exts_get_net(), on other paths it should always return
true, so we don't need to care.

Cc: Lucas Bates <luc...@mojatatu.com>
Cc: Jamal Hadi Salim <j...@mojatatu.com>
Cc: Jiri Pirko <j...@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
 net/sched/cls_flow.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/net/sched/cls_flow.c b/net/sched/cls_flow.c
index 67f3a2af6aab..85f765cff697 100644
--- a/net/sched/cls_flow.c
+++ b/net/sched/cls_flow.c
@@ -372,15 +372,21 @@ static const struct nla_policy flow_policy[TCA_FLOW_MAX + 
1] = {
        [TCA_FLOW_PERTURB]      = { .type = NLA_U32 },
 };
 
-static void flow_destroy_filter_work(struct work_struct *work)
+static void __flow_destroy_filter(struct flow_filter *f)
 {
-       struct flow_filter *f = container_of(work, struct flow_filter, work);
-
-       rtnl_lock();
        del_timer_sync(&f->perturb_timer);
        tcf_exts_destroy(&f->exts);
        tcf_em_tree_destroy(&f->ematches);
+       tcf_exts_put_net(&f->exts);
        kfree(f);
+}
+
+static void flow_destroy_filter_work(struct work_struct *work)
+{
+       struct flow_filter *f = container_of(work, struct flow_filter, work);
+
+       rtnl_lock();
+       __flow_destroy_filter(f);
        rtnl_unlock();
 }
 
@@ -552,8 +558,10 @@ static int flow_change(struct net *net, struct sk_buff 
*in_skb,
 
        *arg = fnew;
 
-       if (fold)
+       if (fold) {
+               tcf_exts_get_net(&fold->exts);
                call_rcu(&fold->rcu, flow_destroy_filter);
+       }
        return 0;
 
 err2:
@@ -570,6 +578,7 @@ static int flow_delete(struct tcf_proto *tp, void *arg, 
bool *last)
        struct flow_filter *f = arg;
 
        list_del_rcu(&f->list);
+       tcf_exts_get_net(&f->exts);
        call_rcu(&f->rcu, flow_destroy_filter);
        *last = list_empty(&head->filters);
        return 0;
@@ -594,7 +603,10 @@ static void flow_destroy(struct tcf_proto *tp)
 
        list_for_each_entry_safe(f, next, &head->filters, list) {
                list_del_rcu(&f->list);
-               call_rcu(&f->rcu, flow_destroy_filter);
+               if (tcf_exts_get_net(&f->exts))
+                       call_rcu(&f->rcu, flow_destroy_filter);
+               else
+                       __flow_destroy_filter(f);
        }
        kfree_rcu(head, rcu);
 }
-- 
2.13.0