CVE-2007-4571 in Linux
Summary
by MITRE
The snd_mem_proc_read function in sound/core/memalloc.c in the Advanced Linux Sound Architecture (ALSA) in the Linux kernel before 2.6.22.8 does not return the correct write size, which allows local users to obtain sensitive information (kernel memory contents) via a small count argument, as demonstrated by multiple reads of /proc/driver/snd-page-alloc.
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Analysis
by VulDB Data Team • 12/31/2024
The vulnerability described in CVE-2007-4571 represents a critical information disclosure flaw within the Advanced Linux Sound Architecture implementation in the Linux kernel. This issue affects versions prior to 2.6.22.8 and specifically targets the snd_mem_proc_read function located in sound/core/memalloc.c. The flaw manifests when the function fails to properly handle the write size parameter, creating a condition where local attackers can exploit the system to access kernel memory contents through carefully crafted read operations against the /proc/driver/snd-page-alloc interface.
The technical mechanism behind this vulnerability stems from improper boundary checking and size calculation within the kernel's sound subsystem. When a user-space application attempts to read from the /proc/driver/snd-page-alloc file descriptor with a small count argument, the snd_mem_proc_read function does not correctly account for the actual amount of data that should be written to the user buffer. This discrepancy allows attackers to perform multiple read operations that gradually expose kernel memory contents, effectively creating a memory disclosure attack vector. The vulnerability is classified under CWE-200, which deals with the exposure of sensitive information to an unauthorized actor, and aligns with ATT&CK technique T1005 for data from local system.
The operational impact of this vulnerability is significant for systems running affected kernel versions, as it provides local users with access to potentially sensitive kernel memory regions. This information disclosure can lead to various downstream security implications including the potential exposure of cryptographic keys, credentials, or other confidential data stored within kernel memory. Attackers could leverage this vulnerability to gain insights into the kernel's internal state, memory layout, and potentially identify other vulnerabilities through pattern analysis of the leaked information. The attack requires local system access but does not need elevated privileges, making it particularly concerning for multi-user environments where privilege separation is expected.
Mitigation strategies for CVE-2007-4571 primarily focus on kernel version updates, with the most effective solution being the upgrade to Linux kernel version 2.6.22.8 or later where the vulnerability has been patched. System administrators should prioritize patching affected systems, especially in environments where local access is possible or where the systems handle sensitive data. Additionally, implementing proper access controls and monitoring for unusual read operations against /proc filesystem entries can help detect potential exploitation attempts. The fix implemented in the patched kernel versions corrects the size calculation logic in the snd_mem_proc_read function to properly handle the write size parameter, preventing the information disclosure that occurred due to the incorrect boundary handling. Organizations should also consider implementing kernel hardening measures such as stack canaries and address space layout randomization to further reduce the attack surface and potential impact of similar vulnerabilities.