ALSA: pcm: oss: Limit the period size to 16MB

Kernel Updated 02 Oct 2025

Summary

19/12/2021

Disclosed on

N/A

Severity

No i

Fix available

Unrated

Severity

Not published

CVSS Score

GSD-2021-1002383: ALSA: pcm: oss: Limit the period size to 16MB. Affects Kernel versions < b02a41eebcc36d4f07196780f2e165ca2c499257. No fix is published. How to fix ↓

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Background

The ALSA (Advanced Linux Sound Architecture) is a software framework and part of the Linux kernel that provides an API for sound card drivers. It allows applications to communicate with sound devices and perform audio-related tasks. The PCM (Pulse Code Modulation) subsystem within ALSA handles digital audio data streams. The OSS (Open Sound System) is a deprecated audio interface for Unix-like operating systems, including Linux. This vulnerability affects the ALSA PCM OSS module, which provides compatibility with legacy OSS applications.

The vulnerability in the ALSA PCM OSS module allows an attacker to set an excessively large period size, leading to a potential heap overflow. By exploiting this vulnerability, an attacker may be able to execute arbitrary code with kernel privileges or cause a denial-of-service condition.

Vulnerability Detail

The vulnerability arises from a lack of proper input validation in the ALSA PCM OSS module. When an application requests a period size larger than the allowed limit of 16MB, the module fails to handle it correctly, leading to a heap overflow. This can be exploited by an attacker to execute arbitrary code with kernel privileges or cause a denial-of-service condition.

The impact of this vulnerability depends on the attacker's ability to interact with the affected system and the privileges they possess. Successful exploitation could result in a complete compromise of the system or disruption of audio functionality.

How To Fix

No fixed version is published for this vulnerability.

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Workaround

As a workaround, users can disable the ALSA PCM OSS module by removing or blacklisting the corresponding kernel module. This can be achieved by modifying the kernel configuration or using tools like modprobe or rmmod to unload the module. However, disabling the ALSA PCM OSS module may impact compatibility with legacy OSS applications that rely on it.

Conclusion

The ALSA PCM OSS module in the Linux kernel is vulnerable to a heap overflow when an excessively large period size is requested. This can be exploited by an attacker to execute arbitrary code with kernel privileges or cause a denial-of-service condition. It is recommended to update the Linux kernel to version v4.9.293 or later to fix this vulnerability. Users can also disable the ALSA PCM OSS module as a workaround, but this may affect compatibility with legacy OSS applications. For further support on vulnerability remediation, please contact DevNack.com.

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