cls_flow: use tcf_exts_get_net() before call_rcu()

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 <lucasb@mojatatu.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files 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);
 }