ALSA: pcm: oss: Fix negative period/buffer sizes in Kernel
Summary
GSD-2021-1002428: ALSA: pcm: oss: Fix negative period/buffer sizes. Affects Kernel versions < f96c0959c1ee92adc911c10d6ec209af50105049. No fix is published. How to fix ↓
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Background
The Kernel is a critical component of the Linux operating system that provides core functionalities and interfaces with hardware devices. It manages various aspects of system operation, including process management, memory management, and device drivers. The Advanced Linux Sound Architecture (ALSA) is a part of the Kernel that provides audio support for Linux-based systems. The PCM (Pulse Code Modulation) subsystem within ALSA handles audio data streaming between applications and audio devices. The OSS (Open Sound System) emulation layer in ALSA allows applications that use the legacy OSS API to work with modern sound systems. However, a vulnerability has been discovered in the PCM OSS code that can lead to negative period/buffer sizes.
Vulnerability Detail
The vulnerability in the PCM OSS code of ALSA allows for negative period/buffer sizes. This can result in various issues, including memory corruption, buffer overflows, and crashes. An attacker may be able to exploit this vulnerability to execute arbitrary code, escalate privileges, or cause a denial-of-service condition. The vulnerability has been fixed in Linux Kernel version v4.19.221 by commit f96c0959c1ee92adc911c10d6ec209af50105049.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
If updating the Kernel is not immediately feasible, a possible workaround is to disable the PCM OSS code by blacklisting the 'snd_pcm_oss' module. This can be done by adding the following line to the '/etc/modprobe.d/blacklist.conf' file:
blacklist snd_pcm_oss
After making this change, restart the system for the blacklist to take effect. However, it is strongly recommended to update the Kernel as soon as possible to ensure the latest security fixes and improvements are applied.
Conclusion
The vulnerability in the PCM OSS code of the Linux Kernel can lead to various security issues and should be addressed promptly. It is recommended to update the Kernel to version v4.19.221 or later by applying the fix commit. If immediate update is not possible, disabling the PCM OSS code can serve as a temporary workaround. For further support on vulnerability remediation, please contact DevNack.com.
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FAQ
ALSA (Advanced Linux Sound Architecture) is a part of the Linux Kernel that provides audio support. The PCM (Pulse Code Modulation) subsystem within ALSA handles audio data streaming between applications and audio devices.
The OSS (Open Sound System) emulation layer in ALSA allows applications that use the legacy OSS API to work with modern sound systems.
Negative period/buffer sizes refer to the size of audio data chunks that are processed or stored. In the context of this vulnerability, negative sizes can lead to memory corruption, buffer overflows, and crashes.
The vulnerability can be exploited by an attacker to execute arbitrary code, escalate privileges, or cause a denial-of-service condition. It is important to update the Kernel to prevent these potential consequences.
To update the Linux Kernel, you need to apply the specific commit (f96c0959c1ee92adc911c10d6ec209af50105049) that fixes the vulnerability to the Kernel source code and recompile the Kernel. Detailed instructions can be found in the Kernel documentation or community resources.
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