Safe RET Interrupt Vulnerability

Summary

An external researcher has reported a potential vulnerability affecting AMD "Zen" architecture processors. The report claims that an attacker executing code on an affected system could inject an interrupt at a precise moment to disrupt “Safe RET,” the default Linux mitigation for Speculative Return Stack Overflow (SRSO), which could potentially weaken that protection and  may result in information disclosure. The researcher states that this behavior was demonstrated on "Zen 1" and "Zen 2" processors and suggests that "Zen 3" and "Zen 4" could also be affected, although this has not been demonstrated.

Based on AMD’s current assessment, the reported issue appears to be associated with the Linux implementation of the Safe RET mitigation.

Affected Products and Mitigation

AMD "Zen 1" - "Zen 4" processors

Acknowledgement 

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

• External Researcher: Daniël Trujillo of MIT CSAIL

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