NVIDIA GPUs with GDDR memories have been shown susceptible to Rowhammer-based bit-flips, similar to CPUs. However, Rowhammer exploits on GPUs have been limited to injecting untargeted bit-flips in victim data like weights of machine learning models, to degrade model accuracy, unlike CPU exploits shown capable of privilege escalation. In this paper, we demonstrate that GPU Rowhammer exploits can be as potent as CPU Rowhammer attacks. By exploiting the GPU page table management to identify when and where new page tables are allocated, we enable an unprivileged user CUDA kernel of one process to use RowHammer bit-flips to gain access to the GPU memory of other processes or co-tenants via targeted tampering of such page-tables resident on the GPU memory. Using this newly found primitive, we demonstrate the first GPU-side privilege escalation attacks, leaking secret data such as cryptographic keys from cuPQC libraries, and even tampering with the model's GPU assembly code to degrade models more stealthily than previous attacks. We further demonstrate that GPU-side privilege escalation can lead to CPU-side privilege escalation, defeating the protections provided by the IOMMU, enabling a malicious user-level program with GPU access to gain root shell and system-wide control, even in a non-multi-tenant setting.

JEDEC has introduced the Per Row Activation Counting (PRAC) framework for DDR5 and future DRAMs to enable precise counting of DRAM row activations. PRAC enables a holistic mitigation of Rowhammer attacks even at ultra-low Rowhammer thresholds. PRAC uses an Alert Back-Off (ABO) protocol to request the memory controller to issue Rowhammer mitigation requests. However, recent PRAC implementations are either insecure or impractical. For example, Panopticon, the inspiration for PRAC, is rendered insecure if implemented per JEDEC’s PRAC specification. On the other hand, the recent UPRAC proposal is impractical since it needs oracular knowledge of the ‘top- N ‘ activated DRAM rows that require mitigation.This paper provides the first secure, scalable, and practical RowHammer solution using the PRAC framework. The crux of our proposal is the design of a priority-based service queue (PSQ) for mitigations that prioritizes pending mitigations based on activation counts to avoid the security risks of prior solutions. This provides principled security using the reactive ABO protocol. Furthermore, we co-design our PSQ, with opportunistic mitigation on Refresh Management (RFM) operations and proactive mitigation during refresh (REF), to limit the performance impact of ABO-based mitigations. QPRAC provides secure and practical RowHammer mitigation that scales to Rowhammer thresholds as low as 71 while incurring a $0.8 \%$ slowdown for benign workloads, which further reduces to $0 \%$ with proactive mitigations.

Super-resolution (SR) problem still faces a challenge of wisely utilizing diverse learned priors to recover the lost details in low resolution images. In this work, we propose a novel method using low rank decomposition which integrates diverse priors learned from external and internal learning to construct SR image. The proposed method first applies an external dictionary learning to get the meta-detail that is commonly shared among images, and then introduces an internal prior learning to learn the local self-similarity (local structure) that is shared in the image. Both are essential but different priors for SR image construction. With these priors, a bank of preliminary HR images are obtained but with estimation errors and noise. To restrain the errors and noise, we consider these HR images as a high dimension data in dimension reduction problem, and solve it using a low rank decomposition. Experimental results show the proposed method preserves image details effectively, also outperforms state-of-the-arts in both visual and quantitative assessments, especially in dealing with the noise.

Features are important for polarimetric synthetic aperture radar (PolSAR) image classification. Various methods focus on extracting feature artificially. Compared with them, we have developed a method to learn feature automatically. The method is based on deep learning which can learn multilayer features. In this paper, stacked sparse autoencoder (SAE) as one of the deep learning models is applied as a useful strategy to achieve the goal. For improving the classification result, we use a small amount of labels to fine-tuning the parameters of the proposed method. Finally, a real PolSAR dataset is used to verify the effectiveness. Experiment result confirms that the proposed method provides noteworthy improvements in classification accuracy and visual effect.