nfc: fix refcount leak in llcp_sock_bind()

stable inclusion
from linux-4.19.187
commit adbb1d218c5f56dbae052765da83c0f57fce2a31
CVE: CVE-2020-25670

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

commit c33b1cc6 upstream.

nfc_llcp_local_get() is invoked in llcp_sock_bind(),
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-2020-25670
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

@@ -120,11 +120,13 @@ static int llcp_sock_bind(struct socket *sock, struct sockaddr *addr, int alen)
 					  llcp_sock->service_name_len,
 					  GFP_KERNEL);
 	if (!llcp_sock->service_name) {
+		nfc_llcp_local_put(llcp_sock->local);
 		ret = -ENOMEM;
 		goto put_dev;
 	}
 	llcp_sock->ssap = nfc_llcp_get_sdp_ssap(local, llcp_sock);
 	if (llcp_sock->ssap == LLCP_SAP_MAX) {
+		nfc_llcp_local_put(llcp_sock->local);
 		kfree(llcp_sock->service_name);
 		llcp_sock->service_name = NULL;
 		ret = -EADDRINUSE;