CVE-2012-6647 in Linux
Summary
by MITRE
The futex_wait_requeue_pi function in kernel/futex.c in the Linux kernel before 3.5.1 does not ensure that calls have two different futex addresses, which allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact via a crafted FUTEX_WAIT_REQUEUE_PI command.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 06/19/2021
The vulnerability identified as CVE-2012-6647 resides within the Linux kernel's futex subsystem, specifically in the futex_wait_requeue_pi function located in kernel/futex.c. This flaw represents a critical security issue affecting Linux kernel versions prior to 3.5.1, where the kernel fails to properly validate the futex addresses used in the FUTEX_WAIT_REQUEUE_PI system call. The vulnerability stems from insufficient input validation that permits the function to process futex operations with identical addresses, creating a scenario where the kernel's internal state management becomes compromised. This condition violates fundamental security principles by allowing unauthorized code execution paths that can lead to system instability and potential privilege escalation.
The technical implementation of this vulnerability exploits the improper handling of futex requeue operations within the kernel's concurrent synchronization mechanisms. When a crafted FUTEX_WAIT_REQUEUE_PI command is executed with two identical futex addresses, the kernel's futex_wait_requeue_pi function fails to validate the address parameters properly. This validation failure results in a NULL pointer dereference condition that occurs during the requeue operation processing. The underlying cause aligns with CWE-476, which describes NULL pointer dereference vulnerabilities, and demonstrates how improper input validation can lead to kernel-level crashes. The function's inability to distinguish between valid and invalid futex address combinations creates a path where malicious local users can manipulate the kernel's internal data structures through crafted system calls.
Operationally, this vulnerability presents significant risks to system stability and availability. Local attackers can leverage this flaw to trigger system crashes through NULL pointer dereference conditions, effectively causing denial of service attacks against the targeted system. The impact extends beyond simple system crashes, as the vulnerability may potentially allow for unspecified other impacts that could include privilege escalation or information disclosure. The vulnerability's local nature means that any user with access to the system can exploit it, making it particularly dangerous in multi-user environments where privilege separation is crucial. The attack vector requires only local system access and the ability to make system calls, making exploitation straightforward and difficult to detect. This aligns with ATT&CK technique T1068, which covers local privilege escalation, and demonstrates how kernel-level vulnerabilities can be exploited to gain unauthorized system access.
Mitigation strategies for CVE-2012-6647 primarily focus on kernel version updates and system hardening measures. The most effective solution involves upgrading to Linux kernel version 3.5.1 or later, where the vulnerability has been patched through proper address validation in the futex_wait_requeue_pi function. System administrators should implement comprehensive patch management processes to ensure all systems receive timely kernel updates. Additional mitigations include implementing strict access controls to limit local user privileges, monitoring for suspicious system call patterns, and employing intrusion detection systems that can identify potential exploitation attempts. The patch addresses the root cause by ensuring that the futex_wait_requeue_pi function properly validates that the two futex addresses are distinct before proceeding with the requeue operation, thereby preventing the NULL pointer dereference condition that leads to system crashes. Organizations should also consider implementing kernel lockdown mechanisms and disabling unnecessary system calls to reduce the attack surface available for exploitation.