Prefetcher Side Channel Attack

Summary

Researchers have shared with AMD a paper titled “GhostFetch: Uncovering and Exploiting the Physical-Address-Indexed Prefetcher to Break AMD SEV-SNP” which describes a prefetcher-based hardware side channel attack.

In their paper the researchers describe a method of using shared prefetcher state to determine whether the virtual address of a load matches the expected address, or whether a load access pattern matches an expected stride.  Either check requires multiple runs but potentially results in loss of confidentiality if the targeted code has either a secret dependent branch or a load access pattern that is secret dependent.

AMD believes that the researchers have not identified any AMD prefetchers that have not already been disclosed in the Software Optimization Guide and did not identify any new security implications with AMD prefetchers.

Acknowledgement   

AMD thanks the following for reporting this issue and engaging in coordinated vulnerability disclosure:

Yu Jin, Tsinghua University
Kaiyuan Zhang, Southern University of Science and Technology
Chang Liu, Tsinghua University
Yinshuai Li, Southern University of Science and Technology
Shuwen Deng, Tsinghua University
Yinqian Zhang, Southern University of Science and Technology (SUSTech)
Yun Chen, The Hong Kong University of Science and Technology (Guangzhou)

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