CVE-2012-5517 in Linux
Summary
by MITRE
The online_pages function in mm/memory_hotplug.c in the Linux kernel before 3.6 allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact in opportunistic circumstances by using memory that was hot-added by an administrator.
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Analysis
by VulDB Data Team • 12/21/2021
The vulnerability identified as CVE-2012-5517 resides within the Linux kernel's memory management subsystem, specifically in the online_pages function located in mm/memory_hotplug.c. This flaw affects Linux kernel versions prior to 3.6 and represents a critical security issue that can be exploited by local attackers to disrupt system operations. The vulnerability is classified under CWE-476 which deals with NULL pointer dereferences, making it a fundamental memory safety issue that can lead to system instability and potential privilege escalation.
The technical implementation of this vulnerability stems from improper handling of memory hot-plug operations within the kernel. When administrators add memory to a running system through hot-add functionality, the online_pages function processes this new memory allocation. However, the function fails to properly validate or initialize memory regions that have been hot-added, creating opportunities for NULL pointer dereference conditions. This occurs because the kernel does not adequately check whether the memory pages being processed have been properly allocated or initialized before attempting to access them. The flaw specifically manifests when local users can manipulate the memory hot-plug interface to trigger the problematic code path, leading to system crashes or potential privilege escalation in opportunistic scenarios.
The operational impact of CVE-2012-5517 extends beyond simple denial of service conditions, as it can potentially enable more sophisticated attacks depending on system configuration and attacker privileges. Local users who can access the memory hot-plug interface or manipulate memory management operations can cause system crashes that may be exploited for privilege escalation or persistent denial of service attacks. The vulnerability's exploitation requires local access but can be particularly dangerous in multi-user environments where unprivileged users might gain access to memory management interfaces. The system crash resulting from NULL pointer dereference can lead to complete system instability, requiring manual intervention for recovery and potentially exposing the system to further compromise.
Mitigation strategies for CVE-2012-5517 primarily focus on kernel version updates and access control measures. Organizations should immediately upgrade to Linux kernel version 3.6 or later where this vulnerability has been addressed through proper memory validation and initialization procedures. System administrators should also implement strict access controls to memory hot-plug interfaces and monitor for unauthorized memory management activities. The fix implemented in kernel 3.6 involves enhanced validation of memory regions before processing and proper initialization of hot-added memory pages, preventing the NULL pointer dereference conditions that led to system crashes. Additionally, security monitoring tools should be configured to detect unusual memory management activities that might indicate exploitation attempts, aligning with attack techniques documented in the MITRE ATT&CK framework under system reconnaissance and privilege escalation tactics.