ALSA: pcm: oss: Fix negative period/buffer sizes in Kernel
Summary
GSD-2021-1002365: ALSA: pcm: oss: Fix negative period/buffer sizes. Affects Kernel versions < be8869d388593e57223ad39297c8e54be632f2f2. No fix is published. How to fix ↓
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Background
The Kernel is a crucial component of the Linux operating system that provides core functionalities and acts as an interface between hardware and software. It manages system resources, including memory, processes, and device drivers. The Advanced Linux Sound Architecture (ALSA) is a part of the Kernel that provides audio support for Linux-based systems. ALSA's PCM (Pulse Code Modulation) subsystem handles audio data transfer between applications and sound hardware. The OSS (Open Sound System) emulation layer within ALSA allows compatibility with older applications that use the OSS API. However, a vulnerability has been identified in the OSS emulation layer that could lead to negative period/buffer sizes.
Vulnerability Detail
The vulnerability in the ALSA PCM OSS emulation layer allows for negative period/buffer sizes. This issue arises due to improper handling of period and buffer size calculations, which can result in a negative value. An attacker could potentially exploit this vulnerability to cause a denial-of-service (DoS) condition or execute arbitrary code with kernel-level privileges. The impact and attack plausibility of this vulnerability have not been proven yet. It is important to note that this vulnerability has been fixed in the Linux Kernel version v4.4.295 by commit be8869d388593e57223ad39297c8e54be632f2f2.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a workaround, users can disable the OSS emulation layer in ALSA by modifying the kernel configuration. This can be achieved by deselecting the 'Sound card support' and 'Open Sound System (DEPRECATED)' options in the kernel configuration menu. However, this workaround may impact compatibility with older applications that rely on the OSS API.
Conclusion
The ALSA PCM OSS emulation layer vulnerability, which allowed for negative period/buffer sizes, has been addressed in the Linux Kernel version v4.4.295. It is crucial to update the Kernel to the fixed version to mitigate the risk of potential exploitation. For further support and assistance in vulnerability remediation, please contact DevNack.com.
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FAQ
The ALSA PCM OSS emulation layer is a component of the Advanced Linux Sound Architecture (ALSA) that provides compatibility with applications using the Open Sound System (OSS) API. It allows older applications to interface with the modern ALSA subsystem for audio functionality.
Period and buffer sizes refer to the amount of audio data that can be processed or stored at a time. Negative sizes indicate a calculation or handling error, which can lead to unexpected behavior or vulnerabilities.
This vulnerability could potentially be exploited by an attacker to cause a denial-of-service (DoS) condition or execute arbitrary code with kernel-level privileges. However, the actual impact and attack plausibility have not been proven yet.
Yes, this vulnerability has been fixed in the Linux Kernel version v4.4.295 by commit be8869d388593e57223ad39297c8e54be632f2f2.
Yes, a workaround is to disable the OSS emulation layer in ALSA by modifying the kernel configuration. However, this may impact compatibility with older applications that rely on the OSS API.
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