Improper Locking of NBIO Devices Could Allow Privileged Remapping Attacks

Summary

A security issue was identified in certain platforms where multiple devices within the Northbridge I/O (NBIO) subsystem may not have their associated lock mechanisms properly enforced. These devices include configuration interfaces that are intended to be restricted after initialization through dedicated lock register controls provided by the platform.

If these lock registers are not correctly set, a privileged attacker could modify device configuration settings that are expected to remain immutable during normal operation. Such conditions may enable the use of these devices in remapping-based attacks, potentially allowing unauthorized access to or manipulation of system memory.

Exploitation of this issue could impact data confidentiality, integrity, or availability, depending on the specific system configuration and usage context.

Acknowledgement 

AMD thanks the reporter, who has asked to remain anonymous, for reporting this issue and engaging in coordinated vulnerability disclosure.

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