CVE-2022-49291 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
ALSA: pcm: Fix races among concurrent hw_params and hw_free calls
Currently we have neither proper check nor protection against the concurrent calls of PCM hw_params and hw_free ioctls, which may result in a UAF. Since the existing PCM stream lock can't be used for protecting the whole ioctl operations, we need a new mutex to protect those racy calls.
This patch introduced a new mutex, runtime->buffer_mutex, and applies it to both hw_params and hw_free ioctl code paths. Along with it, the both functions are slightly modified (the mmap_count check is moved into the state-check block) for code simplicity.
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Analysis
by VulDB Data Team • 02/26/2025
The vulnerability identified as CVE-2022-49291 represents a critical race condition within the Linux kernel's Advanced Linux Sound Architecture (ALSA) subsystem, specifically affecting PCM (Pulse Code Modulation) device drivers. This flaw exists in the kernel's handling of concurrent hardware parameter and hardware free ioctl operations, creating a potential use-after-free (UAF) condition that could be exploited by malicious actors. The vulnerability impacts the core audio subsystem functionality and demonstrates a fundamental flaw in the synchronization mechanisms protecting shared resources during critical audio device operations.
The technical root cause of this vulnerability stems from the absence of proper synchronization mechanisms between concurrent calls to PCM hw_params and hw_free ioctls. These ioctl operations are used to configure hardware parameters and free hardware resources respectively, but the existing PCM stream lock proves insufficient for protecting the entire ioctl operation sequence. The race condition occurs when multiple threads or processes attempt to simultaneously execute these operations on the same PCM device, leading to unpredictable memory access patterns and potential memory corruption. This type of vulnerability maps directly to CWE-362, which describes a race condition where multiple threads access shared resources without proper synchronization, and aligns with ATT&CK technique T1059.003 for process injection and T1068 for privilege escalation through kernel exploits.
The operational impact of this vulnerability extends beyond simple audio functionality degradation, as it creates potential pathways for privilege escalation and system compromise. When a UAF condition occurs in kernel space, attackers can manipulate memory layouts to execute arbitrary code with kernel privileges, potentially leading to complete system takeover. The vulnerability affects systems running Linux kernels with ALSA support, particularly those handling concurrent audio operations from multiple processes or applications. The introduced fix addresses this by implementing a new mutex called runtime->buffer_mutex that specifically protects the critical sections of both hw_params and hw_free ioctl code paths, ensuring proper serialization of these operations.
The mitigation strategy involves applying the kernel patch that introduces the new runtime->buffer_mutex synchronization mechanism, which properly protects the hw_params and hw_free ioctl operations from concurrent access. This solution modifies both functions by moving the mmap_count check into the state-check block, simplifying the code structure while ensuring proper synchronization. Organizations should prioritize updating their Linux kernel versions to include this fix, particularly those running systems with intensive audio processing requirements or multi-user environments where concurrent audio operations are common. The fix demonstrates proper adherence to kernel security principles by implementing targeted synchronization rather than broad system-wide changes, minimizing performance impact while effectively addressing the race condition vulnerability.