CVE-2016-2544 in Android
Summary
by MITRE
Race condition in the queue_delete function in sound/core/seq/seq_queue.c in the Linux kernel before 4.4.1 allows local users to cause a denial of service (use-after-free and system crash) by making an ioctl call at a certain time.
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Analysis
by VulDB Data Team • 09/12/2022
The vulnerability identified as CVE-2016-2544 represents a critical race condition flaw within the Linux kernel's sound subsystem, specifically in the queue_delete function located at sound/core/seq/seq_queue.c. This issue affects kernel versions prior to 4.4.1 and demonstrates a fundamental concurrency problem that can be exploited by local attackers to execute denial of service attacks. The vulnerability arises from improper synchronization mechanisms during the deletion of sequence queues, creating a window where concurrent operations can lead to unpredictable system behavior.
The technical implementation of this race condition occurs when the queue_delete function processes ioctl calls without adequate locking mechanisms to prevent simultaneous access from multiple execution contexts. When a local user crafts specific timing conditions during ioctl operations, the function can attempt to free memory resources while other threads may still be referencing them, resulting in use-after-free conditions. This memory corruption scenario directly translates to system crashes and potential kernel panics, as the freed memory structures become invalid for subsequent operations. The vulnerability specifically targets the ALSA (Advanced Linux Sound Architecture) subsystem's sequencer component, which handles MIDI and audio event processing, making it particularly concerning for multimedia applications and systems requiring reliable audio processing.
From an operational perspective, this vulnerability presents significant risks to system stability and availability, as local users can reliably trigger system crashes without requiring special privileges or complex exploitation techniques. The attack surface is broad since any application utilizing the ALSA sequencer interface could potentially be leveraged to execute the exploit, making it particularly dangerous in multi-user environments or systems where untrusted processes might have access to audio subsystems. The impact extends beyond simple service disruption to potentially compromising the entire system's integrity, as kernel memory corruption can lead to unpredictable behavior including privilege escalation opportunities or data loss. This vulnerability aligns with CWE-362, which specifically addresses race conditions in concurrent programming, and demonstrates how inadequate synchronization can lead to severe security implications.
Mitigation strategies for CVE-2016-2544 primarily focus on kernel version updates to 4.4.1 or later, where the race condition has been properly addressed through enhanced locking mechanisms and proper resource management. System administrators should prioritize patching affected systems immediately, particularly in production environments where audio processing is critical. Additional defensive measures include implementing proper access controls to limit user access to audio subsystems, monitoring for unusual ioctl activity patterns, and maintaining robust system monitoring to detect potential exploitation attempts. The fix implemented in the patched kernel versions demonstrates proper adherence to secure coding practices by ensuring that all resource deallocation operations are properly synchronized and that no references remain to freed memory structures. Organizations should also consider implementing intrusion detection systems that can identify suspicious ioctl call patterns and maintain comprehensive system logging to track potential exploitation attempts, aligning with ATT&CK technique T1059 for command and scripting interpreter usage in potentially malicious contexts.