net/sched: cls_u32: fix possible leak in u32_init_knode()

[ Upstream commit ec5b0f605b105457f257f2870acad4a5d463984b ]

While investigating a related syzbot report,
I found that whenever call to tcf_exts_init()
from u32_init_knode() is failing, we end up
with an elevated refcount on ht->refcnt

To avoid that, only increase the refcount after
all possible errors have been evaluated.

Fixes: b9a24bb76bf6 ("net_sched: properly handle failure case of tcf_exts_init()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 81f933ebee058157e2e7a100ef69249b42f5e85f..5d30db0d71574f756ea3abbf73e81b726a66d272 100644 (file)
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -814,10 +814,6 @@ static struct tc_u_knode *u32_init_knode(struct net *net, struct tcf_proto *tp,
        new->flags = n->flags;
        RCU_INIT_POINTER(new->ht_down, ht);
 
-       /* bump reference count as long as we hold pointer to structure */
-       if (ht)
-               ht->refcnt++;
-
 #ifdef CONFIG_CLS_U32_PERF
        /* Statistics may be incremented by readers during update
         * so we must keep them in tact. When the node is later destroyed
@@ -839,6 +835,10 @@ static struct tc_u_knode *u32_init_knode(struct net *net, struct tcf_proto *tp,
                return NULL;
        }
 
+       /* bump reference count as long as we hold pointer to structure */
+       if (ht)
+               ht->refcnt++;
+
        return new;
 }