Description

In the Linux kernel, the following vulnerability has been resolved: x86/MCE: Always save CS register on AMD Zen IF Poison errors The Instruction Fetch (IF) units on current AMD Zen-based systems do not guarantee a synchronous #MC is delivered for poison consumption errors. Therefore, MCG_STATUS[EIPV|RIPV] will not be set. However, the microarchitecture does guarantee that the exception is delivered within the same context. In other words, the exact rIP is not known, but the context is known to not have changed. There is no architecturally-defined method to determine this behavior. The Code Segment (CS) register is always valid on such IF unit poison errors regardless of the value of MCG_STATUS[EIPV|RIPV]. Add a quirk to save the CS register for poison consumption from the IF unit banks. This is needed to properly determine the context of the error. Otherwise, the severity grading function will assume the context is IN_KERNEL due to the m->cs value being 0 (the initialized value). This leads to unnecessary kernel panics on data poison errors due to the kernel believing the poison consumption occurred in kernel context.

Affected Products 3

References 4

• git.kernel.org https://git.kernel.org/stable/c/2e01bdf7203c383e9d8489d9f963c52d6c81e4db
  Patch
• git.kernel.org https://git.kernel.org/stable/c/4240e2ebe67941ce2c4f5c866c3af4b5ac7a0c67
  Patch
• git.kernel.org https://git.kernel.org/stable/c/6eac3965901489ae114a664a78cd2d1415d1af5c
  Patch
• git.kernel.org https://git.kernel.org/stable/c/e6e6a5f50f58fadec397b23064b7e4830292863d
  Patch

Remediation

• git.kernel.org https://git.kernel.org/stable/c/2e01bdf7203c383e9d8489d9f963c52d6c81e4db
  Patch
• git.kernel.org https://git.kernel.org/stable/c/4240e2ebe67941ce2c4f5c866c3af4b5ac7a0c67
  Patch
• git.kernel.org https://git.kernel.org/stable/c/6eac3965901489ae114a664a78cd2d1415d1af5c
  Patch
• git.kernel.org https://git.kernel.org/stable/c/e6e6a5f50f58fadec397b23064b7e4830292863d
  Patch