[Patch net 03/13] cls_basic: 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_basic.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/net/sched/cls_basic.c b/net/sched/cls_basic.c
index f177649a2419..e43c56d5b96a 100644
--- a/net/sched/cls_basic.c
+++ b/net/sched/cls_basic.c
@@ -85,16 +85,21 @@ static int basic_init(struct tcf_proto *tp)
        return 0;
 }
 
+static void __basic_delete_filter(struct basic_filter *f)
+{
+       tcf_exts_destroy(&f->exts);
+       tcf_em_tree_destroy(&f->ematches);
+       tcf_exts_put_net(&f->exts);
+       kfree(f);
+}
+
 static void basic_delete_filter_work(struct work_struct *work)
 {
        struct basic_filter *f = container_of(work, struct basic_filter, work);
 
        rtnl_lock();
-       tcf_exts_destroy(&f->exts);
-       tcf_em_tree_destroy(&f->ematches);
+       __basic_delete_filter(f);
        rtnl_unlock();
-
-       kfree(f);
 }
 
 static void basic_delete_filter(struct rcu_head *head)
@@ -113,7 +118,10 @@ static void basic_destroy(struct tcf_proto *tp)
        list_for_each_entry_safe(f, n, &head->flist, link) {
                list_del_rcu(&f->link);
                tcf_unbind_filter(tp, &f->res);
-               call_rcu(&f->rcu, basic_delete_filter);
+               if (tcf_exts_get_net(&f->exts))
+                       call_rcu(&f->rcu, basic_delete_filter);
+               else
+                       __basic_delete_filter(f);
        }
        kfree_rcu(head, rcu);
 }
@@ -125,6 +133,7 @@ static int basic_delete(struct tcf_proto *tp, void *arg, 
bool *last)
 
        list_del_rcu(&f->link);
        tcf_unbind_filter(tp, &f->res);
+       tcf_exts_get_net(&f->exts);
        call_rcu(&f->rcu, basic_delete_filter);
        *last = list_empty(&head->flist);
        return 0;
@@ -219,6 +228,7 @@ static int basic_change(struct net *net, struct sk_buff 
*in_skb,
        if (fold) {
                list_replace_rcu(&fold->link, &fnew->link);
                tcf_unbind_filter(tp, &fold->res);
+               tcf_exts_get_net(&fold->exts);
                call_rcu(&fold->rcu, basic_delete_filter);
        } else {
                list_add_rcu(&fnew->link, &head->flist);
-- 
2.13.0