sunrpc: handle ENOMEM in rpcb_getport_async

BugLink: https://bugs.launchpad.net/bugs/1818797

commit 81c88b18 upstream.

If we ignore the error we'll hit a null dereference a little later.

Reported-by: syzbot+4b98281f2401ab849f4b@syzkaller.appspotmail.com
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

net/sunrpc/rpcb_clnt.c

@@ -772,6 +772,12 @@ void rpcb_getport_async(struct rpc_task *task)
 	case RPCBVERS_3:
 		map->r_netid = xprt->address_strings[RPC_DISPLAY_NETID];
 		map->r_addr = rpc_sockaddr2uaddr(sap, GFP_ATOMIC);
+		if (!map->r_addr) {
+			status = -ENOMEM;
+			dprintk("RPC: %5u %s: no memory available\n",
+				task->tk_pid, __func__);
+			goto bailout_free_args;
+		}
 		map->r_owner = "";
 		break;
 	case RPCBVERS_2:
@@ -794,6 +800,8 @@ void rpcb_getport_async(struct rpc_task *task)
 	rpc_put_task(child);
 	return;
 
+bailout_free_args:
+	kfree(map);
 bailout_release_client:
 	rpc_release_client(rpcb_clnt);
 bailout_nofree: