[Patch net 04/13] cls_bpf: 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_bpf.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
index 037a3ae86829..990eb4d91d54 100644
--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -249,6 +249,7 @@ static int cls_bpf_init(struct tcf_proto *tp)
 static void __cls_bpf_delete_prog(struct cls_bpf_prog *prog)
 {
        tcf_exts_destroy(&prog->exts);
+       tcf_exts_put_net(&prog->exts);
 
        if (cls_bpf_is_ebpf(prog))
                bpf_prog_put(prog->filter);
@@ -282,7 +283,10 @@ static void __cls_bpf_delete(struct tcf_proto *tp, struct 
cls_bpf_prog *prog)
        cls_bpf_stop_offload(tp, prog);
        list_del_rcu(&prog->link);
        tcf_unbind_filter(tp, &prog->res);
-       call_rcu(&prog->rcu, cls_bpf_delete_prog_rcu);
+       if (tcf_exts_get_net(&prog->exts))
+               call_rcu(&prog->rcu, cls_bpf_delete_prog_rcu);
+       else
+               __cls_bpf_delete_prog(prog);
 }
 
 static int cls_bpf_delete(struct tcf_proto *tp, void *arg, bool *last)
@@ -516,6 +520,7 @@ static int cls_bpf_change(struct net *net, struct sk_buff 
*in_skb,
        if (oldprog) {
                list_replace_rcu(&oldprog->link, &prog->link);
                tcf_unbind_filter(tp, &oldprog->res);
+               tcf_exts_get_net(&oldprog->exts);
                call_rcu(&oldprog->rcu, cls_bpf_delete_prog_rcu);
        } else {
                list_add_rcu(&prog->link, &head->plist);
-- 
2.13.0