CVE-2021-47008

Summary

In the Linux kernel, the following vulnerability has been resolved:

KVM: SVM: Make sure GHCB is mapped before updating

Access to the GHCB is mainly in the VMGEXIT path and it is known that the GHCB will be mapped. But there are two paths where it is possible the GHCB might not be mapped.

The sev_vcpu_deliver_sipi_vector() routine will update the GHCB to inform the caller of the AP Reset Hold NAE event that a SIPI has been delivered. However, if a SIPI is performed without a corresponding AP Reset Hold, then the GHCB might not be mapped (depending on the previous VMEXIT), which will result in a NULL pointer dereference.

The svm_complete_emulated_msr() routine will update the GHCB to inform the caller of a RDMSR/WRMSR operation about any errors. While it is likely that the GHCB will be mapped in this situation, add a safe guard in this path to be certain a NULL pointer dereference is not encountered.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxf1c6366e304328de301be362eca905a3503ff33b < fb9e14f4f8217a0980f8da2c8ff70dee058cbe47affected
LinuxLinuxf1c6366e304328de301be362eca905a3503ff33b < fd722a57fe0b80133dacae4e1c852ee4212f9b2eaffected
LinuxLinuxf1c6366e304328de301be362eca905a3503ff33b < a3ba26ecfb569f4aa3f867e80c02aa65f20aadadaffected
LinuxLinux5.11affected
LinuxLinux0 < 5.11unaffected
LinuxLinux5.11.22 <= 5.11.*unaffected
LinuxLinux5.12.5 <= 5.12.*unaffected
LinuxLinux5.13 <= *unaffected

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References