CVE-2015-5697 in Linux
Summary
by MITRE
The get_bitmap_file function in drivers/md/md.c in the Linux kernel before 4.1.6 does not initialize a certain bitmap data structure, which allows local users to obtain sensitive information from kernel memory via a GET_BITMAP_FILE ioctl call.
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Analysis
by VulDB Data Team • 06/07/2022
The vulnerability identified as CVE-2015-5697 resides within the Linux kernel's md driver component, specifically in the get_bitmap_file function located in drivers/md/md.c. This flaw represents a classic information disclosure vulnerability that affects Linux kernel versions prior to 4.1.6, creating a pathway for local attackers to extract sensitive data from kernel memory spaces. The issue manifests through improper initialization of a bitmap data structure, which leaves memory contents uninitialized and potentially accessible to malicious processes.
The technical implementation of this vulnerability stems from the failure to properly initialize kernel data structures before processing ioctl commands. When a GET_BITMAP_FILE ioctl call is made to the md driver, the get_bitmap_file function does not adequately initialize all members of the bitmap data structure, resulting in uninitialized memory being returned to userspace. This uninitialized memory may contain remnants of previous kernel operations, configuration data, cryptographic keys, or other sensitive information that was previously stored in those memory locations. The vulnerability falls under the category of information disclosure as defined by CWE-200, specifically involving uninitialized memory exposure.
From an operational perspective, this vulnerability presents a significant risk to systems running affected kernel versions, as local users can exploit it to gain access to kernel memory contents that should remain confidential. The attack requires local system access, making it a privilege escalation vector rather than a remote exploit, but it can be leveraged by malicious users with legitimate access to the system. The impact extends beyond simple information disclosure, as the leaked kernel memory may contain sensitive cryptographic material, system configuration details, or other data that could aid in further exploitation attempts. This vulnerability aligns with ATT&CK technique T1005 for data from local system and T1059 for command and scripting interpreter, as it enables attackers to extract sensitive information that could be used for subsequent attacks.
The exploitation of this vulnerability demonstrates the critical importance of proper memory initialization in kernel space operations. Kernel developers must ensure that all data structures are properly initialized before being exposed to userspace operations, particularly when dealing with ioctl interfaces that can be manipulated by local processes. The vulnerability highlights the need for comprehensive code reviews focusing on memory management practices and the implementation of robust input validation. System administrators should prioritize updating to kernel versions 4.1.6 or later where this vulnerability has been patched, as the fix involves proper initialization of the bitmap data structure. Organizations should implement regular kernel updates and maintain awareness of security advisories to prevent exploitation of similar uninitialized memory vulnerabilities that could compromise system integrity and confidentiality. The vulnerability serves as a reminder of how seemingly minor initialization oversights in kernel code can create significant security implications for system security posture and data protection mechanisms.