CVE-2009-2287 in Linux
Summary
by MITRE
The kvm_arch_vcpu_ioctl_set_sregs function in the KVM in Linux kernel 2.6 before 2.6.30, when running on x86 systems, does not validate the page table root in a KVM_SET_SREGS call, which allows local users to cause a denial of service (crash or hang) via a crafted cr3 value, which triggers a NULL pointer dereference in the gfn_to_rmap function.
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Analysis
by VulDB Data Team • 08/12/2021
The vulnerability described in CVE-2009-2287 represents a critical flaw in the Kernel-based Virtual Machine (KVM) implementation within the Linux kernel version 2.6.0 through 2.6.29. This issue specifically affects x86 systems that utilize KVM for virtualization capabilities. The vulnerability resides in the kvm_arch_vcpu_ioctl_set_sregs function which handles the setting of segment registers for virtual cpu instances. When a local user executes a KVM_SET_SREGS ioctl call with a crafted cr3 value, the kernel fails to properly validate the page table root, creating an exploitable condition that can be leveraged for denial of service attacks. The flaw manifests as a NULL pointer dereference within the gfn_to_rmap function, which occurs when the kernel attempts to translate guest physical frame numbers to reverse mapping structures without proper validation of the input parameters. This vulnerability directly impacts the stability and reliability of virtualized environments where KVM is utilized, potentially allowing malicious users to crash the entire system or cause it to hang indefinitely.
The technical nature of this vulnerability can be categorized under CWE-125 as an out-of-bounds read, though more specifically it represents a NULL pointer dereference that occurs due to insufficient input validation. The flaw operates at the kernel level within the virtualization subsystem, making it particularly dangerous as it can be exploited by local users who have access to the system. The cr3 register contains the page table base address for the current process, and when an attacker supplies an invalid or crafted cr3 value, the KVM subsystem fails to validate this critical piece of information before proceeding with memory management operations. The gfn_to_rmap function serves as a crucial translation layer between guest physical addresses and host kernel mappings, and its failure due to improper input validation creates a cascading effect that leads to system instability. This vulnerability demonstrates a classic example of inadequate input sanitization within kernel space, where user-supplied data is not properly validated before being used in critical system operations.
From an operational perspective, this vulnerability poses significant risks to systems running KVM virtualization environments, particularly in multi-tenant hosting scenarios or environments where local user access cannot be fully trusted. The denial of service impact can result in complete system crashes or indefinite hangs that require manual intervention to resolve, potentially leading to service disruption and data loss. Attackers can exploit this vulnerability to disrupt virtualized services, causing cascading failures in cloud computing environments where multiple virtual machines share the same physical host. The local nature of the exploit means that any user with access to the system can potentially trigger the vulnerability, making it particularly concerning for shared hosting environments or systems where privilege escalation is possible. This vulnerability essentially allows a low-privilege user to compromise the stability of the entire virtualization infrastructure, making it a critical security concern for organizations relying on KVM-based virtualization technologies.
The mitigation strategy for CVE-2009-2287 primarily involves upgrading to Linux kernel version 2.6.30 or later, where the vulnerability has been patched by implementing proper validation of the page table root in the KVM subsystem. The fix introduced in the patched kernel versions ensures that the cr3 value is properly validated before being used in memory management operations, preventing the NULL pointer dereference that led to system crashes. System administrators should also implement proper access controls to limit local user privileges and monitor for unusual system behavior that might indicate exploitation attempts. Additionally, organizations should consider implementing intrusion detection systems that can monitor for suspicious KVM ioctl calls and other virtualization-related activities that might indicate attempts to exploit this vulnerability. The vulnerability highlights the importance of input validation in kernel space and serves as a reminder that even seemingly benign operations like setting segment registers can have catastrophic consequences if not properly validated. This issue aligns with ATT&CK technique T1059.003 for executing commands through virtualization and emphasizes the need for robust kernel security measures in virtualized environments. Organizations should also perform regular security assessments of their virtualization infrastructure and ensure that all kernel components are kept up to date with the latest security patches to prevent exploitation of similar vulnerabilities in the future.