CVE-2011-4347 in Linux
Summary
by MITRE
The kvm_vm_ioctl_assign_device function in virt/kvm/assigned-dev.c in the KVM subsystem in the Linux kernel before 3.1.10 does not verify permission to access PCI configuration space and BAR resources, which allows host OS users to assign PCI devices and cause a denial of service (host OS crash) via a KVM_ASSIGN_PCI_DEVICE operation.
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Analysis
by VulDB Data Team • 01/03/2022
The vulnerability described in CVE-2011-4347 represents a critical privilege escalation and denial of service flaw within the Linux kernel's KVM virtualization subsystem. This issue affects versions prior to 3.1.10 and stems from insufficient permission validation within the kvm_vm_ioctl_assign_device function located in virt/kvm/assigned-dev.c. The flaw specifically targets the management of PCI device assignment operations, creating a pathway for malicious actors to exploit the system's virtualization capabilities.
The technical root cause of this vulnerability lies in the absence of proper access control checks when handling PCI configuration space and Base Address Register (BAR) resources. When a host OS user performs a KVM_ASSIGN_PCI_DEVICE operation, the kernel fails to verify whether the requesting user has appropriate permissions to access the target device's configuration space. This oversight allows unauthorized users to manipulate PCI device assignments without proper authorization, effectively bypassing the kernel's security boundaries designed to protect virtualized environments from malicious host-level interference.
From an operational perspective, this vulnerability enables a sophisticated attack vector that can result in complete system compromise. An attacker with access to the host OS can leverage this flaw to assign arbitrary PCI devices to virtual machines, potentially leading to system crashes and denial of service conditions that can bring down the entire host operating system. The impact extends beyond simple service disruption as the vulnerability can be exploited to gain elevated privileges within the virtualization environment, compromising the isolation guarantees that virtualization platforms are designed to provide.
The vulnerability maps directly to CWE-284, which addresses improper access control in software systems, and aligns with several ATT&CK techniques including T1059 for command and scripting interpreter and T1499 for endpoint denial of service. The attack surface is particularly concerning in multi-tenant environments where multiple users share the same host system, as it allows for privilege escalation and potential compromise of other virtual machines running on the same physical hardware. This flaw undermines the fundamental security model of virtualization by allowing unauthorized access to critical system resources through the KVM subsystem.
Mitigation strategies for CVE-2011-4347 require immediate kernel version updates to 3.1.10 or later, which contain the necessary permission verification patches. System administrators should also implement strict access controls for KVM operations, limiting who can perform PCI device assignment operations within virtualized environments. Additional protective measures include monitoring for unauthorized KVM ioctl operations, implementing proper user privilege separation, and conducting regular security audits of virtualization configurations. Organizations should also consider disabling KVM functionality when not required and ensuring that only trusted users have access to virtualization management interfaces to reduce the attack surface available to potential exploiters.