CVE-2021-46977: KVM: VMX: Disable preemption when probing user return MSRs
In the Linux kernel, the following vulnerability has been resolved:
KVM: VMX: Disable preemption when probing user return MSRs
Disable preemption when probing a user return MSR via RDSMR/WRMSR. If the MSR holds a different value per logical CPU, the WRMSR could corrupt the host's value if KVM is preempted between the RDMSR and WRMSR, and then rescheduled on a different CPU.
Opportunistically land the helper in common x86, SVM will use the helper in a future commit.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Linux kernel KVM: VMXto a version that resolves this vulnerability.Patch KVM: VMX: Disable preemption when probing user return MSRs - Configuration
Ensure KVM disables CPU preemption while probing user return MSRs (between RDMSR and WRMSR) to prevent WRMSR writing a logical-CPU-specific MSR value onto a different CPU after rescheduling.
KVM on Linux (VMX path) Disable preemption during RDMSR->WRMSR probing of user return MSRs = enabled
Event History
Frequently Asked Questions
What is the severity of CVE-2021-46977?
CVE-2021-46977 has a medium severity level due to potential privilege escalation risks.
How do I fix CVE-2021-46977?
To fix CVE-2021-46977, update the Linux kernel to a version beyond 5.13-rc1, 5.12.5, 5.11.22, or 5.10.38.
Which versions of the Linux kernel are affected by CVE-2021-46977?
CVE-2021-46977 affects Linux kernel versions 5.5 to 5.10.38, 5.11 to 5.11.22, and 5.12 to 5.12.5.
What type of vulnerability is CVE-2021-46977?
CVE-2021-46977 is a vulnerability related to KVM (Kernel-based Virtual Machine) that impacts the handling of user return MSRs.
Can CVE-2021-46977 lead to system compromise?
Yes, CVE-2021-46977 can potentially allow a local attacker to escalate privileges on the affected system.