CVE-2011-0463 in Linux
Summary
by MITRE
The ocfs2_prepare_page_for_write function in fs/ocfs2/aops.c in the Oracle Cluster File System 2 (OCFS2) subsystem in the Linux kernel before 2.6.39-rc1 does not properly handle holes that cross page boundaries, which allows local users to obtain potentially sensitive information from uninitialized disk locations by reading a file.
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Analysis
by VulDB Data Team • 10/21/2021
The vulnerability described in CVE-2011-0463 represents a critical information disclosure flaw within the Oracle Cluster File System 2 implementation in the Linux kernel. This issue specifically affects the ocfs2_prepare_page_for_write function located in fs/ocfs2/aops.c, which is responsible for preparing pages for write operations within the OCFS2 subsystem. The flaw manifests when dealing with file holes that span across multiple page boundaries, creating a scenario where uninitialized memory contents can be inadvertently exposed to local users. The vulnerability exists in kernel versions prior to 2.6.39-rc1, indicating a long-standing issue that affected numerous production systems running older kernel versions. This type of information disclosure vulnerability is particularly concerning because it can expose sensitive data that may include system memory contents, cryptographic keys, or other confidential information stored in uninitialized disk sectors.
The technical root cause of this vulnerability stems from improper handling of file hole boundaries during page preparation operations. When the ocfs2_prepare_page_for_write function encounters a file hole that crosses page boundaries, it fails to properly initialize or clear memory regions that should remain uninitialized. This occurs because the function does not adequately account for the boundary conditions when processing file operations, leading to memory that was previously used for other purposes remaining in the file data when it should have been cleared or properly handled. The issue is classified under CWE-200, which deals with the exposure of sensitive information to an unauthorized actor, and represents a classic case of information leakage through improper memory management. The flaw allows local attackers to read uninitialized disk locations, which can contain remnants of previous file contents, system memory, or other sensitive data that was previously stored in those memory regions.
From an operational impact perspective, this vulnerability poses significant security risks to systems running affected kernel versions, particularly in enterprise environments where OCFS2 is commonly deployed for high-availability file storage solutions. Local users with access to the system can exploit this vulnerability to gain access to potentially sensitive information that may include remnants of other files, system credentials, cryptographic material, or other confidential data stored in the uninitialized memory regions. The attack vector is relatively straightforward as it requires only local access to the system, making it particularly dangerous in multi-tenant environments or systems where local privilege escalation is possible. The vulnerability can be exploited to perform information gathering attacks that may reveal system internals, user data, or other sensitive information that could be leveraged for further attacks. This type of vulnerability aligns with ATT&CK technique T1005, which involves data from local system sources, and demonstrates how seemingly benign file system operations can expose critical information.
The recommended mitigation strategy involves upgrading to a kernel version that is not affected by this vulnerability, specifically kernel version 2.6.39-rc1 or later where the fix has been implemented. System administrators should prioritize patching affected systems, particularly in environments where OCFS2 is actively used for cluster file system operations. Additionally, organizations should implement monitoring to detect unusual file access patterns that might indicate exploitation attempts. The fix in the patched kernel versions properly handles file hole boundaries and ensures that uninitialized memory regions are appropriately cleared or managed during page preparation operations. Security teams should also consider implementing additional access controls and monitoring for systems running older kernel versions while patches are being deployed. Regular kernel updates and vulnerability assessments are essential to maintain system security posture and prevent exploitation of similar memory handling flaws that may exist in other kernel subsystems.