netdev - [PATCH net-next 04/11] netfilter: cttimeout: inc/dec module refcount per object, not per use refcount

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Date:   Mon, 11 Apr 2022 12:27:37 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, kuba@...nel.org
Subject: [PATCH net-next 04/11] netfilter: cttimeout: inc/dec module refcount per object, not per use refcount

From: Florian Westphal <fw@...len.de>

There is no need to increment the module refcount again, its enough to
obtain one reference per object, i.e. take a reference on object
creation and put it on object destruction.

Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nfnetlink_cttimeout.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c
index b0d8888a539b..eea486f32971 100644
--- a/net/netfilter/nfnetlink_cttimeout.c
+++ b/net/netfilter/nfnetlink_cttimeout.c
@@ -158,6 +158,7 @@ static int cttimeout_new_timeout(struct sk_buff *skb,
 	timeout->timeout.l3num = l3num;
 	timeout->timeout.l4proto = l4proto;
 	refcount_set(&timeout->refcnt, 1);
+	__module_get(THIS_MODULE);
 	list_add_tail_rcu(&timeout->head, &pernet->nfct_timeout_list);
 
 	return 0;
@@ -506,13 +507,8 @@ static struct nf_ct_timeout *ctnl_timeout_find_get(struct net *net,
 		if (strncmp(timeout->name, name, CTNL_TIMEOUT_NAME_MAX) != 0)
 			continue;
 
-		if (!try_module_get(THIS_MODULE))
+		if (!refcount_inc_not_zero(&timeout->refcnt))
 			goto err;
-
-		if (!refcount_inc_not_zero(&timeout->refcnt)) {
-			module_put(THIS_MODULE);
-			goto err;
-		}
 		matching = timeout;
 		break;
 	}
@@ -525,10 +521,10 @@ static void ctnl_timeout_put(struct nf_ct_timeout *t)
 	struct ctnl_timeout *timeout =
 		container_of(t, struct ctnl_timeout, timeout);
 
-	if (refcount_dec_and_test(&timeout->refcnt))
+	if (refcount_dec_and_test(&timeout->refcnt)) {
 		kfree_rcu(timeout, rcu_head);
-
-	module_put(THIS_MODULE);
+		module_put(THIS_MODULE);
+	}
 }
 
 static const struct nfnl_callback cttimeout_cb[IPCTNL_MSG_TIMEOUT_MAX] = {
-- 
2.30.2