[SCSI] libfcoe: fix possible buffer overflow in fcoe_transport_show

possible buffer overflow in fcoe_transport_show when reaching the end of
buffer and crossing PAGE_SIZE boundary.
Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/fcoe/fcoe_transport.c

@@ -385,9 +385,9 @@ static int fcoe_transport_show(char *buffer, const struct kernel_param *kp)
 	i = j = sprintf(buffer, "Attached FCoE transports:");
 	mutex_lock(&ft_mutex);
 	list_for_each_entry(ft, &fcoe_transports, list) {
-		i += snprintf(&buffer[i], IFNAMSIZ, "%s ", ft->name);
-		if (i >= PAGE_SIZE)
+		if (i >= PAGE_SIZE - IFNAMSIZ)
 			break;
+		i += snprintf(&buffer[i], IFNAMSIZ, "%s ", ft->name);
 	}
 	mutex_unlock(&ft_mutex);
 	if (i == j)