net/9p: Return error if we fail to encode protocol data

We need to return error in case we fail to encode data in protocol buffer.
This patch also return error in case of a failed copy_from_user.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

net/9p/client.c

@@ -579,6 +579,8 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
 	va_start(ap, fmt);
 	err = p9pdu_vwritef(req->tc, c->proto_version, fmt, ap);
 	va_end(ap);
+	if (err)
+		goto reterr;
 	p9pdu_finalize(req->tc);
 
 	err = c->trans_mod->request(c, req);

net/9p/protocol.c

@@ -122,9 +122,8 @@ static size_t
 pdu_write_u(struct p9_fcall *pdu, const char __user *udata, size_t size)
 {
 	size_t len = MIN(pdu->capacity - pdu->size, size);
-	int err = copy_from_user(&pdu->sdata[pdu->size], udata, len);
-	if (err)
-		printk(KERN_WARNING "pdu_write_u returning: %d\n", err);
+	if (copy_from_user(&pdu->sdata[pdu->size], udata, len))
+		len = 0;
 
 	pdu->size += len;
 	return size - len;