CVE-2021-47008: KVM: SVM: Make sure GHCB is mapped before updating
First published: Wed Feb 28 2024(Updated: )
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.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux kernel | >=5.11<5.11.22 | |
| Linux kernel | >=5.12<5.12.5 |
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Reference Links
Frequently Asked Questions
What is the severity of CVE-2021-47008?
CVE-2021-47008 is classified as a medium severity vulnerability affecting the Linux kernel.
How do I fix CVE-2021-47008?
To fix CVE-2021-47008, upgrade to the Linux kernel version 5.11.22 or later, or 5.12.6 or later.
What systems are affected by CVE-2021-47008?
CVE-2021-47008 affects versions of the Linux kernel between 5.11 and 5.11.22, and 5.12 and 5.12.5.
Is CVE-2021-47008 exploitable remotely?
CVE-2021-47008 is not considered to be remotely exploitable as it requires local access.
What does CVE-2021-47008 involve?
CVE-2021-47008 involves a flaw in proper mapping of the Guest Hypercall Page Buffer (GHCB) in the Linux kernel's KVM SVM.
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