CVE-2014-8369 in Linux
Summary
by MITRE
The kvm_iommu_map_pages function in virt/kvm/iommu.c in the Linux kernel through 3.17.2 miscalculates the number of pages during the handling of a mapping failure, which allows guest OS users to cause a denial of service (host OS page unpinning) or possibly have unspecified other impact by leveraging guest OS privileges. NOTE: this vulnerability exists because of an incorrect fix for CVE-2014-3601.
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Analysis
by VulDB Data Team • 02/23/2022
The vulnerability described in CVE-2014-8369 represents a critical flaw in the Linux kernel's KVM (Kernel-based Virtual Machine) implementation that specifically affects the iommu (input-output memory management unit) subsystem. This issue manifests in the kvm_iommu_map_pages function located within the virt/kvm/iommu.c file, where the kernel fails to properly calculate the number of pages during mapping operations. The flaw was introduced as an incorrect fix for a previously identified vulnerability CVE-2014-3601, creating a regression that undermines the security and stability of virtualized environments. The vulnerability exists in Linux kernel versions through 3.17.2, making it a widespread concern for systems running these kernel versions.
The technical nature of this vulnerability stems from a miscalculation in page count handling when a mapping failure occurs within the IOMMU subsystem. When the kvm_iommu_map_pages function encounters a mapping error, it incorrectly determines the number of pages that should be processed, leading to improper memory management operations. This miscalculation specifically affects the page unpinning process on the host OS, where the kernel may inadvertently unpin pages that should remain pinned or fail to properly manage the memory mapping state. The flaw leverages guest OS privileges, meaning that an attacker with access to a guest virtual machine can exploit this vulnerability to manipulate the host system's memory management mechanisms.
The operational impact of this vulnerability extends beyond simple denial of service conditions, though DoS is certainly a primary concern. The improper page unpinning can lead to memory corruption, system instability, and potentially more severe consequences depending on the specific memory management patterns of the host system. Attackers with guest privileges can cause the host OS to unpin pages that are still in use, potentially leading to memory access violations, system crashes, or even privilege escalation scenarios. The unspecified other impacts mentioned in the vulnerability description suggest that the memory management corruption could potentially be exploited for more advanced attacks, though the exact scope of these possibilities requires further analysis. This vulnerability directly relates to CWE-129, which addresses improper handling of length values and count variables, and aligns with ATT&CK techniques involving privilege escalation and system resource exhaustion.
The exploitation of this vulnerability demonstrates the complex interdependencies between virtualization components and the host operating system's memory management subsystem. When a guest OS triggers a mapping failure condition, the incorrect page count calculation causes the host to perform improper memory management operations that can cascade into system-wide instability. The vulnerability's existence as a regression from a previous fix indicates that the security community's initial attempt to resolve the issue was incomplete or incorrect, creating a situation where the system becomes more vulnerable than before the original vulnerability was addressed. Mitigation strategies must include kernel updates to versions that properly address this miscalculation, as well as monitoring for abnormal memory management patterns that might indicate exploitation attempts. System administrators should prioritize patching affected systems and implementing additional monitoring controls to detect potential exploitation attempts, particularly in environments where multiple virtual machines are running with varying privilege levels. The vulnerability underscores the importance of thorough testing and validation when implementing security fixes, as incomplete or incorrect fixes can create more dangerous conditions than the original vulnerabilities they were intended to address.