SUNRPC: Don't try to parse incomplete RPC messages

If the copy of the RPC reply into our buffers did not complete, and
we could end up with a truncated message. In that case, just resend
the call.

Fixes: a0584ee ("SUNRPC: Use struct xdr_stream when decoding...")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/clnt.c

@@ -2465,6 +2465,7 @@ call_decode(struct rpc_task *task)
 	struct rpc_clnt	*clnt = task->tk_client;
 	struct rpc_rqst	*req = task->tk_rqstp;
 	struct xdr_stream xdr;
+	int err;
 
 	dprint_status(task);
 
@@ -2487,6 +2488,15 @@ call_decode(struct rpc_task *task)
 	 * before it changed req->rq_reply_bytes_recvd.
 	 */
 	smp_rmb();
+
+	/*
+	 * Did we ever call xprt_complete_rqst()? If not, we should assume
+	 * the message is incomplete.
+	 */
+	err = -EAGAIN;
+	if (!req->rq_reply_bytes_recvd)
+		goto out;
+
 	req->rq_rcv_buf.len = req->rq_private_buf.len;
 
 	/* Check that the softirq receive buffer is valid */
@@ -2495,7 +2505,9 @@ call_decode(struct rpc_task *task)
 
 	xdr_init_decode(&xdr, &req->rq_rcv_buf,
 			req->rq_rcv_buf.head[0].iov_base, req);
-	switch (rpc_decode_header(task, &xdr)) {
+	err = rpc_decode_header(task, &xdr);
+out:
+	switch (err) {
 	case 0:
 		task->tk_action = rpc_exit_task;
 		task->tk_status = rpcauth_unwrap_resp(task, &xdr);