net: sched: fix possible refcount leak in tc_chain_tmplt_add()

stable inclusion
from stable-v4.19.286
commit 3cc54473badeb4cdb3798a079480114f0738432f
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7J5UF
CVE: NA

--------------------------------

[ Upstream commit 44f8baaf ]

try_module_get will be called in tcf_proto_lookup_ops. So module_put needs
to be called to drop the refcount if ops don't implement the required
function.

Fixes: 9f407f17 ("net: sched: introduce chain templates")
Signed-off-by: NHangyu Hua <hbh25y@gmail.com>
Reviewed-by: NLarysa Zaremba <larysa.zaremba@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

net/sched/cls_api.c

@@ -1840,6 +1840,7 @@ static int tc_chain_tmplt_add(struct tcf_chain *chain, struct net *net,
 		return PTR_ERR(ops);
 	if (!ops->tmplt_create || !ops->tmplt_destroy || !ops->tmplt_dump) {
 		NL_SET_ERR_MSG(extack, "Chain templates are not supported with specified classifier");
+		module_put(ops->owner);
 		return -EOPNOTSUPP;
 	}