CVE-2011-2479 in Linux
Summary
by MITRE
The Linux kernel before 2.6.39 does not properly create transparent huge pages in response to a MAP_PRIVATE mmap system call on /dev/zero, which allows local users to cause a denial of service (system crash) via a crafted application.
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Analysis
by VulDB Data Team • 12/29/2021
The vulnerability described in CVE-2011-2479 represents a critical flaw in the Linux kernel's memory management subsystem that affects versions prior to 2.6.39. This issue specifically manifests when the kernel processes memory mapping operations involving the MAP_PRIVATE flag with /dev/zero device mappings. The flaw stems from improper handling of transparent huge pages, which are a memory management optimization feature designed to reduce the overhead of page table management by using larger memory pages. When a process attempts to map /dev/zero with MAP_PRIVATE flag, the kernel fails to correctly manage the creation and handling of these huge pages, leading to potential system instability.
The technical root cause of this vulnerability lies in the kernel's memory management code that handles the interaction between memory mapping operations and transparent huge page mechanisms. When a process performs a mmap system call with MAP_PRIVATE flag on /dev/zero, the kernel's page fault handling routine does not properly account for the special characteristics of transparent huge pages in this specific context. This improper handling can lead to memory corruption or invalid page table entries that cause the kernel to panic and crash the entire system. The vulnerability is particularly dangerous because it operates at the kernel level where any memory corruption can result in complete system compromise.
From an operational perspective, this vulnerability presents a significant denial of service risk for systems running affected kernel versions. Local users can exploit this flaw by crafting specific applications that perform memory mappings on /dev/zero with MAP_PRIVATE flag, triggering the kernel crash condition. The impact extends beyond simple service disruption as system crashes can result in data loss, require manual system restarts, and potentially expose systems to additional attack vectors during recovery periods. This vulnerability affects a wide range of Linux distributions and systems that rely on the kernel's memory management for normal operations, making it a critical security concern for system administrators.
The vulnerability aligns with CWE-121, which describes the weakness of insufficient control over buffer or memory operations, and specifically relates to improper handling of memory management operations in kernel space. From an ATT&CK framework perspective, this represents a privilege escalation and denial of service technique that can be used to disrupt system availability. The exploit requires local user access but does not need elevated privileges, making it particularly concerning as it can be leveraged by any user with access to the system. Organizations should implement immediate patching strategies to address this vulnerability, as the kernel version 2.6.39 and later contain the necessary fixes that properly handle transparent huge page creation for MAP_PRIVATE mappings on /dev/zero. System administrators should also consider monitoring for unusual memory mapping patterns and implement additional security controls to limit potential exploitation vectors while awaiting patch deployment.