SUNRPC: Fix a re-entrancy bug in xs_tcp_read_calldir()

If the attempt to read the calldir fails, then instead of storing the read
bytes, we currently discard them. This leads to a garbage final result when
upon re-entry to the same routine, we read the remaining bytes.

Fixes the regression in bugzilla number 16213. Please see
    https://bugzilla.kernel.org/show_bug.cgi?id=16213

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org

net/sunrpc/xprtsock.c

@@ -210,7 +210,8 @@ struct sock_xprt {
 	 * State of TCP reply receive
 	 */
 	__be32			tcp_fraghdr,
-				tcp_xid;
+				tcp_xid,
+				tcp_calldir;
 
 	u32			tcp_offset,
 				tcp_reclen;
@@ -927,7 +928,7 @@ static inline void xs_tcp_read_calldir(struct sock_xprt *transport,
 {
 	size_t len, used;
 	u32 offset;
-	__be32	calldir;
+	char *p;
 
 	/*
 	 * We want transport->tcp_offset to be 8 at the end of this routine
@@ -936,26 +937,33 @@ static inline void xs_tcp_read_calldir(struct sock_xprt *transport,
 	 * transport->tcp_offset is 4 (after having already read the xid).
 	 */
 	offset = transport->tcp_offset - sizeof(transport->tcp_xid);
-	len = sizeof(calldir) - offset;
+	len = sizeof(transport->tcp_calldir) - offset;
 	dprintk("RPC:       reading CALL/REPLY flag (%Zu bytes)\n", len);
-	used = xdr_skb_read_bits(desc, &calldir, len);
+	p = ((char *) &transport->tcp_calldir) + offset;
+	used = xdr_skb_read_bits(desc, p, len);
 	transport->tcp_offset += used;
 	if (used != len)
 		return;
 	transport->tcp_flags &= ~TCP_RCV_READ_CALLDIR;
-	transport->tcp_flags |= TCP_RCV_COPY_CALLDIR;
-	transport->tcp_flags |= TCP_RCV_COPY_DATA;
 	/*
 	 * We don't yet have the XDR buffer, so we will write the calldir
 	 * out after we get the buffer from the 'struct rpc_rqst'
 	 */
-	if (ntohl(calldir) == RPC_REPLY)
+	switch (ntohl(transport->tcp_calldir)) {
+	case RPC_REPLY:
+		transport->tcp_flags |= TCP_RCV_COPY_CALLDIR;
+		transport->tcp_flags |= TCP_RCV_COPY_DATA;
 		transport->tcp_flags |= TCP_RPC_REPLY;
-	else
+		break;
+	case RPC_CALL:
+		transport->tcp_flags |= TCP_RCV_COPY_CALLDIR;
+		transport->tcp_flags |= TCP_RCV_COPY_DATA;
 		transport->tcp_flags &= ~TCP_RPC_REPLY;
-	dprintk("RPC:       reading %s CALL/REPLY flag %08x\n",
-			(transport->tcp_flags & TCP_RPC_REPLY) ?
-				"reply for" : "request with", calldir);
+		break;
+	default:
+		dprintk("RPC:       invalid request message type\n");
+		xprt_force_disconnect(&transport->xprt);
+	}
 	xs_tcp_check_fraghdr(transport);
 }
 
@@ -975,12 +983,10 @@ static inline void xs_tcp_read_common(struct rpc_xprt *xprt,
 		/*
 		 * Save the RPC direction in the XDR buffer
 		 */
-		__be32	calldir = transport->tcp_flags & TCP_RPC_REPLY ?
-					htonl(RPC_REPLY) : 0;
-
 		memcpy(rcvbuf->head[0].iov_base + transport->tcp_copied,
-			&calldir, sizeof(calldir));
-		transport->tcp_copied += sizeof(calldir);
+			&transport->tcp_calldir,
+			sizeof(transport->tcp_calldir));
+		transport->tcp_copied += sizeof(transport->tcp_calldir);
 		transport->tcp_flags &= ~TCP_RCV_COPY_CALLDIR;
 	}