IOMMU Para-Virtualization for Efficient and Secure DMA in Virtual Machines

( Hongwei Tang ),( Qiang Li ),( Shengzhong Feng ),( Xiaofang Zhao ),( Yan Jin ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12

IOMMU is a hardware unit that is indispensable for DMA. Besides address translation and remapping, it also provides I/O virtual address space isolation among devices and memory access control on DMA transactions. However, currently commodity virtualization platforms lack of IOMMU virtualization, so that the virtual machines are vulnerable to DMA security threats. Previous works focus only on DMA security problem of directly assigned devices. Moreover, these solutions either introduce significant overhead or require modifications on the guest OS to optimize performance, and none can achieve high I/O efficiency and good compatibility with the guest OS simultaneously, which are both necessary for production environments. However, for simulated virtual devices the DMA security problem also exists, and previous works cannot solve this problem. The reason behind that is IOMMU circuits on the host do not work for this kind of devices as DMA operations of which are simulated by memory copy of CPU. Motivated by the above observations, we propose an IOMMU para-virtualization solution called PVIOMMU, which provides general functionalities especially DMA security guarantees for both directly assigned devices and simulated devices. The prototype of PVIOMMU is implemented in Qemu/KVM based on the virtio framework and can be dynamically loaded into guest kernel as a module, As a result, modifying and rebuilding guest kernel are not required. In addition, the device model of Qemu is revised to implement DMA access control by separating the device simulator from the address space of the guest virtual machine. Experimental evaluations on three kinds of network devices including Intel I210 (1Gbps), simulated E1000 (1Gbps) and IB ConnectX-3 (40Gbps) show that, PVIOMMU introduces little overhead on DMA transactions, and in general the network I/O performance is close to that in the native KVM implementation without IOMMU virtualization.

IOMMU Para-Virtualization for Efficient and Secure DMA in Virtual Machines

Tang, Hongwei,Li, Qiang,Feng, Shengzhong,Zhao, Xiaofang,Jin, Yan Korean Society for Internet Information 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12

IOMMU is a hardware unit that is indispensable for DMA. Besides address translation and remapping, it also provides I/O virtual address space isolation among devices and memory access control on DMA transactions. However, currently commodity virtualization platforms lack of IOMMU virtualization, so that the virtual machines are vulnerable to DMA security threats. Previous works focus only on DMA security problem of directly assigned devices. Moreover, these solutions either introduce significant overhead or require modifications on the guest OS to optimize performance, and none can achieve high I/O efficiency and good compatibility with the guest OS simultaneously, which are both necessary for production environments. However, for simulated virtual devices the DMA security problem also exists, and previous works cannot solve this problem. The reason behind that is IOMMU circuits on the host do not work for this kind of devices as DMA operations of which are simulated by memory copy of CPU. Motivated by the above observations, we propose an IOMMU para-virtualization solution called PVIOMMU, which provides general functionalities especially DMA security guarantees for both directly assigned devices and simulated devices. The prototype of PVIOMMU is implemented in Qemu/KVM based on the virtio framework and can be dynamically loaded into guest kernel as a module, As a result, modifying and rebuilding guest kernel are not required. In addition, the device model of Qemu is revised to implement DMA access control by separating the device simulator from the address space of the guest virtual machine. Experimental evaluations on three kinds of network devices including Intel I210 (1Gbps), simulated E1000 (1Gbps) and IB ConnectX-3 (40Gbps) show that, PVIOMMU introduces little overhead on DMA transactions, and in general the network I/O performance is close to that in the native KVM implementation without IOMMU virtualization.

VirtAV: an Agentless Runtime Antivirus System for Virtual Machines

( Hongwei Tang ),( Shengzhong Feng ),( Xiaofang Zhao ),( Yan Jin ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.11

Antivirus is an important issue to the security of virtual machine (VM). According to where the antivirus system resides, the existing approaches can be categorized into three classes: internal approach, external approach and hybrid approach. However, for the internal approach, it is susceptible to attacks and may cause antivirus storm and rollback vulnerability problems. On the other hand, for the external approach, the antivirus systems built upon virtual machine introspection (VMI) technology cannot find and prohibit viruses promptly. Although the hybrid approach performs virus scanning out of the virtual machine, it is still vulnerable to attacks since it completely depends on the agent and hooks to deliver events in the guest operating system. To solve the aforementioned problems, based on in-memory signature scanning, we propose an agentless runtime antivirus system VirtAV, which scans each piece of binary codes to execute in guest VMs on the VMM side to detect and prevent viruses. As an external approach, VirtAV does not rely on any hooks or agents in the guest OS, and exposes no attack surface to the outside world, so it guarantees the security of itself to the greatest extent. In addition, it solves the antivirus storm problem and the rollback vulnerability problem in virtualization environment. We implemented a prototype based on Qemu/KVM hypervisor and ClamAV antivirus engine. Experimental results demonstrate that VirtAV is able to detect both user-level and kernel-level virus programs inside Windows and Linux guest, no matter whether they are packed or not. From the performance aspect, the overhead of VirtAV on guest performance is acceptable. Especially, VirtAV has little impact on the performance of common desktop applications, such as video playing, web browsing and Microsoft Office series.

Some remarks on problems of subset sum

Min Tang,Hongwei Xu 대한수학회 2022 대한수학회보 Vol.59 No.6

Let $A=\{a_1<a_2<\cdots\}$ be a sequence of integers and let $P(A)=\left\{\sum \varepsilon_ia_i: a_i\in A, \varepsilon_i=0\text{ or }1, \sum \varepsilon_i<\infty\right\}$. Burr posed the following question: Determine conditions on integers sequence $B$ that imply either the existence or the non-existence of $A$ for which $P(A)$ is the set of all non-negative integers not in $B$. In this paper, we focus on some problems of subset sum related to Burr's question.

Key Assumption to Evaluate the Mechanical Performance of Widened Voided-slab Bridge Due to Foundation Settlement

Wenqing Wu,Hongwei Shan,Song Yang,Zhangxiang Tang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.4

In concrete bridge widening projects, it is a common practice to provide a monolithic connection between the existing and newdecks by casting an in situ concrete stitching slab. As a result, the differential foundation settlement between the two decks has aconsiderable effect on the concrete stitching slab and the widened bridge. The widened bridge noted as multi-girder bridge is asimple-supported, precast, voided-slab bridge, located on the Beijing–Shanghai Expressway in east of China. When using a grillageFinite Element Model (FEM) to model the mechanical behavior of the multi-girder bridge after it has been widened, the generalapproach to account for the effect of differential foundation settlement is to load a calculated forced vertical displacement to thebearing of each precast slab of the new bridge. However, there is no suitable mathematical model to be used for calculating the forceddisplacement for all new slab beams, which requires the ability to describe the transverse distribution mode of these forceddisplacement under a given differential foundation settlement. Under this background, an experimental study and finite elementanalysis are conducted to find this suitable mathematical model in this paper. Based on a comprehensive research results, a quadraticcurve model was considered to be a suitable mathematical model to meet the design need of such type of widened multi-girderbridge, and its quadratic equation was also derived in the paper. This finding is the key assumption for accurately analyzing themechanical behavior of a widened multi-girder bridge, with a grillage finite element model.

Enteric dysbiosis-linked gut barrier disruption triggers early renal injury induced by chronic high salt feeding in mice

Jingjuan Hu,Haihua Luo,Jieyan Wang,Wenli Tang,Junqi Lu,Shan Wu,Zhi Xiong,Guizhi Yang,Zhenguo Chen,Tian Lan,Hongwei Zhou,Jing Nie,Yong Jiang,Peng Chen 생화학분자생물학회 2017 Experimental and molecular medicine Vol.49 No.-

Chronic high-salt diet-associated renal injury is a key risk factor for the development of hypertension. However, the mechanism by which salt triggers kidney damage is poorly understood. Our study investigated how high salt (HS) intake triggers early renal injury by considering the ‘gut-kidney axis’. We fed mice 2% NaCl in drinking water continuously for 8 weeks to induce early renal injury. We found that the ‘quantitative’ and ‘qualitative’ levels of the intestinal microflora were significantly altered after chronic HS feeding, which indicated the occurrence of enteric dysbiosis. In addition, intestinal immunological gene expression was impaired in mice with HS intake. Gut permeability elevation and enteric bacterial translocation into the kidney were detected after chronic HS feeding. Gut bacteria depletion by non-absorbable antibiotic administration restored HS loadinginduced gut leakiness, renal injury and systolic blood pressure elevation. The fecal microbiota from mice fed chronic HS could independently cause gut leakiness and renal injury. Our current work provides a novel insight into the mechanism of HS-induced renal injury by investigating the role of the intestine with enteric bacteria and gut permeability and clearly illustrates that chronic HS loading elicited renal injury and dysfunction that was dependent on the intestine.

An Efficient Somewhat HE scheme over Integers and Its Variation

( Haomiao Yang ),( Hyunsung Kim ),( Dianhua Tang ),( Hongwei Li ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.10

In 2010, Dijk et al. demonstrated a simple somewhat homomorphic encryption (HE) scheme over the integers of which this simplicity came at the cost of a public key size in O(λ¹⁰). Although in 2011 Coron et al. reduced the public key size to O(λ⁷), it is still too large for practical applications, especially for the cloud computing. In this paper, we propose a new form of somewhat HE scheme to reduce further the public key size and a variation of the scheme to optimize the ciphertext size. First of all, we propose a new somewhat HE scheme which is built on the hardness of the approximate greatest common divisor (GCD) problem of two integers, where the public key size in the scheme is reduced to O(λ³). Furthermore, we can reduce the length of the ciphertext of the new somewhat HE scheme by applying the modular reduction technique. Additionally, we give simulation results for evaluating ability of the proposed scheme.

Microstructure and Properties of 2Cr13-xMo Stainless Steels Fabricated by Direct Laser Deposition

Jing Liang,Ziyang Lin,Xiuyuan Yin,Suiyuan Chen,Changsheng Liu,Ruihong Chai,Hongwei Zhang,Guangquan Tang,Kun Tian 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.1

In this paper, 2Cr13 stainless steels with diferent Mo contents (x=0 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%) were fabricated by Direct Laser Deposition (DLD) technology. The efects of Mo element on the microstructure evolution and comprehensive properties such as corrosion resistance and wear resistance of 2Cr13 stainless steel were investigated in detail. The results showed that the microstructure for the DLD 2Cr13 stainless steel was mainly composed of martensite, ferrite,and a small amount of Mo2C and Cr23C6 carbides. With the content of Mo increased from 0.5 to 1.5 wt%, the martensiticmicrostructure was refned and more dispersed Mo2C and Cr23C6 carbides were formed. The average microhardness andcorrosion resistance of the DLD 2Cr13-xMo were increased with the Mo content increased from 0 to 1.0 wt%, and thendecreased when the Mo content exceeded 1.0 wt%. For the DLD 2Cr13-1.0 wt% Mo, the average microhardness reachedup to 620 HV0.2, and the highest corrosion resistance (self-corrosion potential − 0.34 V) was obtained, in which the selfcorrosion potential was 0.05 higher than that of DLD 2Cr13 stainless steel. The wear resistance of the DLD 2Cr13-xMogradually increased with the increase of the Mo, the wear mass loss of DLD 2Cr13-xMo (x=1.0 wt%) was only 37% thatof DLD 2Cr13 stainless steel.

Overexpression of NPC1L1 in the livers of transgenic Bama miniature pigs accelerates lipid peroxidation

Chongli Xu,Yu Liu,Yuchen Gong,Xinping Duan,Xiaochun Tang,Mingjun Zhang,Daxin Pang,Liqing Yu,Hongwei Zhao,Hongsheng Ouyang 한국유전학회 2015 Genes & Genomics Vol.37 No.2

Although Niemann-Pick C1-Like 1 (NPC1L1)plays a key role in intestinal cholesterol absorption, regulatingcholesterol metabolism and maintaining cholesterolmetabolic homeostasis, the molecular mechanism ofNPC1L1 in lipid-metabolism disorders leading to liverdisease remains largely unknown. Previous studies haveshown that NPC1L1 is related with the development offatty liver. Therefore, we hypothesized that NPC1L1 playsan important role in lipid-metabolism disorders and liverdisease by affecting the transcription of certain genesinvolved in lipid synthesis. To further elucidate the functionof NPC1L1, especially in the liver, we used somaticcellnuclear transfer to establish transgenic pigs thatexpressed human NPC1L1 in their livers. We investigatedsuperoxide dismutase activities and the levels of free fattyacids and malondialdehyde, a biomarker of lipid peroxidation. Superoxide dismutase activities significantlydecreased, and free fatty acid and malondialdehyde levelssignificantly increased in the NPC1L1 transgenic pigs,indicating that the overexpression of NPC1L1 in the liverresulted in severe lipid peroxidation. Our findings suggestthat NPC1L1 plays an important role in lipid-metabolismdisorders and liver disease.

PM2.5 in poultry houses synergizes with Pseudomonas aeruginosa to aggravate lung inflammation in mice through the NF-κB pathway

Meng Li,Xiuli Wei,Youzhi Li,Tao Feng,Linlin Jiang,Hongwei Zhu,Xin Yu,Jinxiu Tang,Guozhong Chen,Jianlong Zhang,Xingxiao Zhang 대한수의학회 2020 Journal of Veterinary Science Vol.21 No.3

Background: High concentrations of particulate matter less than 2.5 µm in diameter (PM2.5) in poultry houses is an important cause of respiratory disease in animals and humans. Pseudomonas aeruginosa is an opportunistic pathogen that can induce severe respiratory disease in animals under stress or with abnormal immune functions. When excessively high concentrations of PM2.5 in poultry houses damage the respiratory system and impair host immunity, secondary infections with P. aeruginosa can occur and produce a more intense inflammatory response, resulting in more severe lung injury. Objectives: In this study, we focused on the synergistic induction of inflammatory injury in the respiratory system and the related molecular mechanisms induced by PM2.5 and P. aeruginosa in poultry houses. Methods: High-throughput 16S rDNA sequence analysis was used for characterizing the bacterial diversity and relative abundance of the PM2.5 samples, and the effects of PM2.5 and P. aeruginosa stimulation on inflammation were detected by in vitro and in vivo. Results: Sequencing results indicated that the PM2.5 in poultry houses contained a high abundance of potentially pathogenic genera, such as Pseudomonas (2.94%). The lung tissues of mice had more significant pathological damage when co-stimulated by PM2.5 and P. aeruginosa, and it can increase the expression levels of interleukin (IL)-6, IL-8, and tumor necrosis factor-α through nuclear factor (NF)-κB pathway in vivo and in vitro. Conclusions: The results confirmed that poultry house PM2.5 in combination with P. aeruginosa could aggravate the inflammatory response and cause more severe respiratory system injuries through a process closely related to the activation of the NF-κB pathway.