[Patch net 08/13] cls_fw: 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_fw.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
index 99183b8621ec..7f45e5ab8afc 100644
--- a/net/sched/cls_fw.c
+++ b/net/sched/cls_fw.c
@@ -122,13 +122,19 @@ static int fw_init(struct tcf_proto *tp)
        return 0;
 }
 
+static void __fw_delete_filter(struct fw_filter *f)
+{
+       tcf_exts_destroy(&f->exts);
+       tcf_exts_put_net(&f->exts);
+       kfree(f);
+}
+
 static void fw_delete_filter_work(struct work_struct *work)
 {
        struct fw_filter *f = container_of(work, struct fw_filter, work);
 
        rtnl_lock();
-       tcf_exts_destroy(&f->exts);
-       kfree(f);
+       __fw_delete_filter(f);
        rtnl_unlock();
 }
 
@@ -154,7 +160,10 @@ static void fw_destroy(struct tcf_proto *tp)
                        RCU_INIT_POINTER(head->ht[h],
                                         rtnl_dereference(f->next));
                        tcf_unbind_filter(tp, &f->res);
-                       call_rcu(&f->rcu, fw_delete_filter);
+                       if (tcf_exts_get_net(&f->exts))
+                               call_rcu(&f->rcu, fw_delete_filter);
+                       else
+                               __fw_delete_filter(f);
                }
        }
        kfree_rcu(head, rcu);
@@ -179,6 +188,7 @@ static int fw_delete(struct tcf_proto *tp, void *arg, bool 
*last)
                if (pfp == f) {
                        RCU_INIT_POINTER(*fp, rtnl_dereference(f->next));
                        tcf_unbind_filter(tp, &f->res);
+                       tcf_exts_get_net(&f->exts);
                        call_rcu(&f->rcu, fw_delete_filter);
                        ret = 0;
                        break;
@@ -299,6 +309,7 @@ static int fw_change(struct net *net, struct sk_buff 
*in_skb,
                RCU_INIT_POINTER(fnew->next, rtnl_dereference(pfp->next));
                rcu_assign_pointer(*fp, fnew);
                tcf_unbind_filter(tp, &f->res);
+               tcf_exts_get_net(&f->exts);
                call_rcu(&f->rcu, fw_delete_filter);
 
                *arg = fnew;
-- 
2.13.0