xfrm: fix refcount leak in __xfrm_policy_check()

stable inclusion
from stable-v5.10.140
commit 1305d7d4f35ca6f214a2d23b075aa6a924cff3be
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I63FTT

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1305d7d4f35ca6f214a2d23b075aa6a924cff3be

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

[ Upstream commit 9c9cb23e ]

The issue happens on an error path in __xfrm_policy_check(). When the
fetching process of the object `pols[1]` fails, the function simply
returns 0, forgetting to decrement the reference count of `pols[0]`,
which is incremented earlier by either xfrm_sk_policy_lookup() or
xfrm_policy_lookup(). This may result in memory leaks.

Fix it by decreasing the reference count of `pols[0]` in that path.

Fixes: 134b0fc5 ("IPsec: propagate security module errors up from flow_cache_lookup")
Signed-off-by: NXin Xiong <xiongx18@fudan.edu.cn>
Signed-off-by: NXin Tan <tanxin.ctf@gmail.com>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>

net/xfrm/xfrm_policy.c

@@ -3631,6 +3631,7 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
 		if (pols[1]) {
 			if (IS_ERR(pols[1])) {
 				XFRM_INC_STATS(net, LINUX_MIB_XFRMINPOLERROR);
+				xfrm_pol_put(pols[0]);
 				return 0;
 			}
 			pols[1]->curlft.use_time = ktime_get_real_seconds();