CVE-2024-26691 in Linux
Summary
by MITRE • 04/03/2024
In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: Fix circular locking dependency
The rule inside kvm enforces that the vcpu->mutex is taken *inside* kvm->lock. The rule is violated by the pkvm_create_hyp_vm() which acquires the kvm->lock while already holding the vcpu->mutex lock from kvm_vcpu_ioctl(). Avoid the circular locking dependency altogether by protecting the hyp vm handle with the config_lock, much like we already do for other forms of VM-scoped data.
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Analysis
by VulDB Data Team • 08/03/2025
This vulnerability resides within the Linux kernel's KVM subsystem, specifically affecting the arm64 architecture implementation. The issue manifests as a circular locking dependency that can lead to system instability and potential denial of service conditions. The vulnerability occurs when the kernel attempts to acquire locks in an improper sequence, creating a deadlock scenario that can compromise the entire virtualization environment. Such circular dependencies are particularly dangerous in hypervisor implementations where multiple layers of locking must maintain strict ordering to prevent race conditions and ensure data consistency.
The technical flaw stems from improper lock ordering within the KVM implementation where the vcpu->mutex lock is acquired inside the kvm->lock context. This violates established locking protocols that require consistent lock acquisition order across all kernel subsystems. The specific function pkvm_create_hyp_vm() demonstrates this problematic behavior by holding the vcpu->mutex lock while attempting to acquire the kvm->lock, creating a circular dependency that can result in system hangs. This pattern directly contravenes standard lock ordering principles and can be categorized under CWE-367, which addresses time-of-check to time-of-use vulnerabilities related to improper locking mechanisms.
The operational impact of this vulnerability extends beyond simple system performance degradation to potentially catastrophic system failures. When the circular locking dependency occurs, it can cause the entire kernel to become unresponsive, effectively rendering the virtualization environment unusable. This affects systems running arm64-based virtual machines including cloud infrastructure, containerized environments, and embedded systems that rely on KVM for virtualization capabilities. The vulnerability is particularly concerning in production environments where high availability and system reliability are paramount, as it can lead to unexpected service interruptions and require system restarts to resolve.
Mitigation strategies for this vulnerability focus on implementing proper lock ordering and restructuring the locking mechanisms within the KVM subsystem. The recommended fix involves protecting the hyp vm handle with the config_lock instead of relying on the problematic kvm->lock acquisition pattern. This approach aligns with established best practices for kernel development and follows the principle of least privilege in lock management. Security teams should prioritize patching affected systems, as the vulnerability can potentially be exploited to cause denial of service attacks against virtualized environments. The fix essentially restructures the locking protocol to prevent the circular dependency while maintaining the necessary synchronization for safe concurrent access to virtual machine resources, following ATT&CK technique T1499 for system disruption prevention. Organizations running arm64-based virtualization infrastructure should implement immediate patch management procedures to address this vulnerability and maintain system integrity.