net: sched: don't release reference on action overwrite

Return from action init function with reference to action taken,
even when overwriting existing action.

Action init API initializes its fourth argument (pointer to pointer to tc
action) to either existing action with same index or newly created action.
In case of existing index(and bind argument is zero), init function returns
without incrementing action reference counter. Caller of action init then
proceeds working with action, without actually holding reference to it.
This means that action could be deleted concurrently.

Change action init behavior to always take reference to action before
returning successfully, in order to protect from concurrent deletion.

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 7 deletions

diff --git a/net/sched/act_tunnel_key.c b/net/sched/act_tunnel_key.c
index 655ed0b3fc67..ab5bf5c13f87 100644
--- a/net/sched/act_tunnel_key.c
+++ b/net/sched/act_tunnel_key.c
@@ -329,12 +329,10 @@ static int tunnel_key_init(struct net *net, struct nlattr *nla,
 		}
 
 		ret = ACT_P_CREATED;
-	} else {
+	} else if (!ovr) {
 		tcf_idr_release(*a, bind);
-		if (!ovr) {
-			NL_SET_ERR_MSG(extack, "TC IDR already exists");
-			return -EEXIST;
-		}
+		NL_SET_ERR_MSG(extack, "TC IDR already exists");
+		return -EEXIST;
 	}
 
 	t = to_tunnel_key(*a);
@@ -342,8 +340,7 @@ static int tunnel_key_init(struct net *net, struct nlattr *nla,
 	ASSERT_RTNL();
 	params_new = kzalloc(sizeof(*params_new), GFP_KERNEL);
 	if (unlikely(!params_new)) {
-		if (ret == ACT_P_CREATED)
-			tcf_idr_release(*a, bind);
+		tcf_idr_release(*a, bind);
 		NL_SET_ERR_MSG(extack, "Cannot allocate tunnel key parameters");
 		return -ENOMEM;
 	}