CVE-2013-2146 in Linux
Summary
by MITRE
arch/x86/kernel/cpu/perf_event_intel.c in the Linux kernel before 3.8.9, when the Performance Events Subsystem is enabled, specifies an incorrect bitmask, which allows local users to cause a denial of service (general protection fault and system crash) by attempting to set a reserved bit.
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Analysis
by VulDB Data Team • 05/14/2021
The vulnerability described in CVE-2013-2146 resides within the Linux kernel's performance events subsystem, specifically in the intel.c file located in the x86 kernel architecture. This flaw represents a classic case of improper bit manipulation that can lead to system instability and denial of service conditions. The issue affects Linux kernel versions prior to 3.8.9, making it a significant concern for systems running older kernel versions that have not been properly updated.
The technical root cause of this vulnerability stems from an incorrect bitmask specification within the Performance Events Subsystem's Intel implementation. When performance monitoring units are enabled, the kernel attempts to configure specific hardware registers that control performance event sampling and monitoring capabilities. The flaw occurs during the process of setting up these registers where the kernel incorrectly handles reserved bits within the bitmask structure. These reserved bits are designated by hardware specifications to remain unchanged or to have specific meanings, but the kernel implementation fails to properly mask or validate these bits before applying them to the hardware registers.
When a local user attempts to configure performance events through the subsystem, the kernel processes the requested configuration parameters and applies them to the hardware registers. However, due to the incorrect bitmask handling, reserved bits are inadvertently set to non-zero values, causing the hardware to interpret these configurations as invalid or malformed. This misconfiguration triggers a general protection fault within the kernel's performance event handling code, which results in an immediate system crash and subsequent denial of service condition.
The operational impact of this vulnerability extends beyond simple system crashes as it provides a mechanism for local users to deliberately destabilize systems running affected kernel versions. Since the vulnerability is exploitable by local users, it represents a privilege escalation risk within the context of system security, as any user with access to the system can potentially trigger the condition. The implications are particularly concerning in multi-tenant environments or systems where untrusted users might have access to perform performance monitoring operations, as this could be leveraged to systematically disrupt system availability.
This vulnerability aligns with CWE-129, which addresses improper validation of input ranges, and more specifically relates to CWE-755, indicating improper handling of exceptional conditions. The flaw demonstrates a common pattern in kernel development where bitwise operations are not properly validated against hardware specifications, leading to undefined behavior when hardware registers receive invalid configurations. From an ATT&CK perspective, this vulnerability corresponds to T1499.004, which covers network denial of service attacks, though in this case the attack vector is local rather than network-based.
The recommended mitigations for CVE-2013-2146 involve applying the appropriate kernel updates to versions 3.8.9 or later, where the bitmask handling has been corrected. System administrators should also consider implementing additional security measures such as restricting access to performance monitoring interfaces for untrusted users, monitoring for unusual performance event configuration attempts, and ensuring that all systems are maintained with current security patches. Organizations should also consider implementing kernel lockdown mechanisms or other security frameworks that can prevent unauthorized modification of kernel parameters that could lead to similar vulnerabilities. The fix in the updated kernel versions ensures proper bitmask validation and prevents the setting of reserved bits, thereby eliminating the conditions that lead to the general protection fault and system crash.