Sync+Sync: A Covert Channel Built on fsync with Storage

Scientists have built a variety of covert channels for secretive information transmission with CPU cache and main memory. In this paper, we turn to a lower level in the memory hierarchy, i.e., persistent storage. Most programs store intermediate or eventual results in the form of files and some of them call fsync to synchronously persist a file with storage device for orderly persistence. Our quantitative study shows that one program would undergo significantly longer response time for fsync call if the other program is concurrently calling fsync, although they do not share any data. We further find that, concurrent fsync calls contend at multiple levels of storage stack due to sharing software structures (e.g., Ext4's journal) and hardware resources (e.g., disk's I/O dispatch queue). We accordingly build a covert channel named Sync+Sync. Sync+Sync delivers a transmission bandwidth of 20,000 bits per second at an error rate of about 0.40% with an ordinary solid-state drive. Sync+Sync can be conducted in cross-disk partition, cross-file system, cross-container, cross-virtual machine, and even cross-disk drive fashions, without sharing data between programs. Next, we launch side-channel attacks with Sync+Sync and manage to precisely detect operations of a victim database (e.g., insert/update and B-Tree node split). We also leverage Sync+Sync to distinguish applications and websites with high accuracy by detecting and analyzing their fsync frequencies and flushed data volumes. These attacks are useful to support further fine-grained information leakage.Comment: A full version for the paper with the same title accepted by the 33rd USENIX Security Symposium (USENIX Security 2024

I/O Transit Caching for PMem-based Block Device

Byte-addressable non-volatile memory (NVM) sitting on the memory bus is employed to make persistent memory (PMem) in general-purpose computing systems and embedded systems for data storage. Researchers develop software drivers such as the block translation table (BTT) to build block devices on PMem, so programmers can keep using mature and reliable conventional storage stack while expecting high performance by exploiting fast PMem. However, our quantitative study shows that BTT underutilizes PMem and yields inferior performance, due to the absence of the imperative in-device cache. We add a conventional I/O staging cache made of DRAM space to BTT. As DRAM and PMem have comparable access latency, I/O staging cache is likely to be fully filled over time. Continual cache evictions and fsyncs thus cause on-demand flushes with severe stalls, such that the I/O staging cache is concretely unappealing for PMem-based block devices. We accordingly propose an algorithm named Caiti with novel I/O transit caching. Caiti eagerly evicts buffered data to PMem through CPU's multi-cores. It also conditionally bypasses a full cache and directly writes data into PMem to further alleviate I/O stalls. Experiments confirm that Caiti significantly boosts the performance with BTT by up to 3.6x, without loss of block-level write atomicity.Comment: Accepted by the Journal of Systems Architecture: Embedded Software Design (JSA

Dynamics characteristics of a rotary table motorized spindle with externally pressurized air bearings

The face grinding process depends on high-precision rotary table spindle with a large axial load capacity. This paper develops an ultra-precision rotary table spindle with externally pressurized air bearings consisting of a double-pad thrust bearing and a journal bearing; a vacuum clamp system is designed to locate and hold the workpiece. The dynamic model for the rotor-bearing system has been established by using the Reynolds equation and the rigid-body dynamic theory considering five degrees of freedom (DOF). The effects of static and dynamic behaviors of the spindle with the bearing’s key parameters are analyzed systematically. Finally, an experiment study is conducted to verify the theoretical model

Genomic structure of human lysosomal glycosylasparaginase

AbstractThe gene structure of the human lysosomal enzyme glycosylasparaginase was determined. The gene spans 13 kb and consists of 9 exons. Both 5′ and 3′ untranslated regions of the gene are uninterrupted by introns. A number of transcriptional elements were identified in the 5′ upstream sequence that includes two putative CAAT boxes followed by TATA-like sequences together with two AP-2 binding sites and one for Sp1. A 100 bp CpG island and several ETF binding sites were also found. Additional AP-2 and Sp1 binding sites are present in the first intron. Two polyadenylation sites are present and appear to be functional. The major known glycosylasparaginase gene defect G488→C, which causes the lysosomal storage disease aspartylglycosaminuria (AGU) in Finland, is located in exon 4. Exon 5 encodes the post-translational cleavage site for the formation of the mature α/β subunits of the enzyme as well as a recently proposed active site threonine, Thr206

Metastasis-associated in colon cancer-1 and aldehyde dehydrogenase 1 are metastatic and prognostic biomarker for non-small cell lung cancer

BACKGROUND: Tumor recurrence and metastasis are the most common reason for treatment failure. Metastasis-associate in colon cancer-1 (MACC1) has been identified as a metastatic and prognostic biomarker for colorectal cancer and other solid tumors. Aldehyde dehydrogenase 1 (ALDH1), a marker of cancer stem cells, is also associated with metastasis and poor prognosis in many tumors. However, the prognostic value of either MACC1 or ALDH1 in non-small cell lung cancer (NSCLC) is unclear. In this study, we explored the relationship between MACC1 and ALDH1 expression, as well as their respective associations with clinicopathological features, to determine if either could be useful for improvement of survival prognosis in NSCLC. METHODS: The expression levels of both MACC1 and ALDH1 in 240 whole tissue sections of NSCLC were examined by immunohistochemistry. Clinical data were also collected. RESULTS: MACC1 and ALDH1 were significantly overexpressed in NSCLC tissues when compared to levels in normal lung tissues. Investigation of associations between MACC1 or ALDH1 protein levels with clinicopathological parameters of NSCLC revealed correlations between the expression of each with tumor grade, lymph node metastasis, and tumor node metastasis. The overall survival of patients with MACC1- or ALDH1-positive NSCLC tumors was significantly lower than that of those who were negative. Importantly, multivariate analysis suggested that positive expression of either MACC1 or ALDH1, as well as TNM stage, could be independent prognostic factors for overall survival in patients with NSCLC. CONCLUSIONS: MACC1 and ALDH1 may represent promising metastatic and prognostic biomarkers, as well as potential therapeutic targets, for NSCLC