CVE-2014-4653 in Linux
Summary
by MITRE
sound/core/control.c in the ALSA control implementation in the Linux kernel before 3.15.2 does not ensure possession of a read/write lock, which allows local users to cause a denial of service (use-after-free) and obtain sensitive information from kernel memory by leveraging /dev/snd/controlCX access.
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Analysis
by VulDB Data Team • 01/18/2022
The vulnerability identified as CVE-2014-4653 represents a critical flaw in the Advanced Linux Sound Architecture (ALSA) subsystem of the Linux kernel, specifically within the sound/core/control.c file. This issue affects kernel versions prior to 3.15.2 and stems from improper handling of read/write locks during ALSA control operations. The flaw manifests when local attackers exploit access to /dev/snd/controlCX device files, which are part of the Linux sound subsystem interface that provides control over audio hardware components.
The technical root cause of this vulnerability lies in the absence of proper lock validation within the ALSA control implementation. When multiple processes or threads attempt to access the same control device simultaneously, the kernel fails to properly enforce exclusive access rights. This race condition allows malicious actors to manipulate the timing of read and write operations in such a way that they can trigger a use-after-free condition. The vulnerability specifically targets the control interface that manages audio device parameters, where the kernel does not verify that the calling process actually holds the necessary locks before proceeding with memory operations.
The operational impact of this vulnerability extends beyond simple denial of service to include potential information disclosure from kernel memory space. Local attackers can leverage this flaw to read sensitive data that should remain protected within kernel memory, potentially exposing system configuration details, cryptographic keys, or other confidential information. The use-after-free condition creates an exploitable state where freed memory blocks can be reallocated and accessed by malicious code, leading to unpredictable behavior including system crashes or privilege escalation opportunities. This type of vulnerability aligns with CWE-416, which addresses use-after-free conditions, and represents a classic example of improper lock management in concurrent systems.
Attackers exploiting this vulnerability typically require local access to the system since the flaw resides in kernel-level code that is not exposed to network interfaces. The attack vector involves opening and manipulating the /dev/snd/controlCX device files while carefully orchestrating concurrent access patterns to trigger the race condition. The vulnerability's classification under the ATT&CK framework would fall under privilege escalation and defense evasion techniques, as successful exploitation could potentially lead to elevated privileges and system compromise. Organizations should prioritize patching affected systems to kernel versions 3.15.2 or later, as this vulnerability has been widely documented and exploited in various security assessments. The fix implemented in the patched kernel versions addresses the missing lock validation and ensures proper synchronization mechanisms are in place to prevent concurrent access violations that lead to the use-after-free condition and information disclosure risks.
This vulnerability demonstrates the importance of proper synchronization primitives in kernel code and highlights how seemingly minor oversights in lock management can lead to significant security implications. The ALSA subsystem's design requires careful attention to concurrent access patterns, as audio device controls often need to be manipulated in real-time while maintaining system stability and security boundaries. System administrators should consider implementing additional monitoring for unusual access patterns to audio control devices, as this vulnerability could potentially be used as a stepping stone for more sophisticated attacks. The security community has classified this as a medium to high severity issue due to its potential for both service disruption and information disclosure, making it a priority for immediate remediation across affected Linux installations.