nfc: fix refcount leak in llcp_sock_connect()

stable inclusion
from linux-4.19.187
commit c14b50185cd0d5ba6d7a5eb8acf9fbcc3663416d
CVE: CVE-2020-25671

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

commit 8a4cd82d upstream.

nfc_llcp_local_get() is invoked in llcp_sock_connect(),
but nfc_llcp_local_put() is not invoked in subsequent failure branches.
As a result, refcount leakage occurs.
To fix it, add calling nfc_llcp_local_put().

fix CVE-2020-25671
Fixes: c7aa1225 ("NFC: Take a reference on the LLCP local pointer when creating a socket")
Reported-by: N"kiyin(尹亮)" <kiyin@tencent.com>
Link: https://www.openwall.com/lists/oss-security/2020/11/01/1
Cc: <stable@vger.kernel.org> #v3.6
Signed-off-by: NXiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: NYue Haibing <yuehaibing@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/nfc/llcp_sock.c

@@ -716,6 +716,7 @@ static int llcp_sock_connect(struct socket *sock, struct sockaddr *_addr,
 	llcp_sock->local = nfc_llcp_local_get(local);
 	llcp_sock->ssap = nfc_llcp_get_local_ssap(local);
 	if (llcp_sock->ssap == LLCP_SAP_MAX) {
+		nfc_llcp_local_put(llcp_sock->local);
 		ret = -ENOMEM;
 		goto put_dev;
 	}
@@ -753,6 +754,7 @@ static int llcp_sock_connect(struct socket *sock, struct sockaddr *_addr,
 
 sock_unlink:
 	nfc_llcp_put_ssap(local, llcp_sock->ssap);
+	nfc_llcp_local_put(llcp_sock->local);
 
 	nfc_llcp_sock_unlink(&local->connecting_sockets, sk);