CVE-2011-1012 in Linux
Summary
by MITRE
The ldm_parse_vmdb function in fs/partitions/ldm.c in the Linux kernel before 2.6.38-rc6-git6 does not validate the VBLK size value in the VMDB structure in an LDM partition table, which allows local users to cause a denial of service (divide-by-zero error and OOPS) via a crafted partition table.
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Analysis
by VulDB Data Team • 10/18/2021
The vulnerability described in CVE-2011-1012 resides within the Linux kernel's Logical Disk Manager partition handling code, specifically in the ldm_parse_vmdb function located in fs/partitions/ldm.c. This flaw represents a classic input validation issue that affects the kernel's ability to properly parse and process Logical Disk Manager partition tables. The vulnerability manifests when the kernel encounters a crafted partition table that contains malformed VBLK (Virtual Block) size values within the VMDB (Virtual Machine Database) structure. The absence of proper validation for this critical parameter creates an exploitable condition that can be leveraged by local attackers to disrupt system operations.
The technical root cause of this vulnerability stems from the function's failure to validate the VBLK size value before proceeding with calculations and data processing. When the ldm_parse_vmdb function processes the VMDB structure, it directly uses the VBLK size value without verifying its legitimacy or ensuring it meets expected constraints. This lack of validation creates a scenario where a maliciously crafted partition table can contain a zero or invalid VBLK size value that, when processed, leads to a divide-by-zero error. Such errors in kernel space typically result in system crashes or kernel oops conditions, which are unrecoverable faults that force the operating system to terminate or reboot.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a potential vector for more sophisticated attacks within kernel space. Local attackers who can manipulate partition table data or gain access to systems with vulnerable kernel versions can trigger system instability through carefully constructed partition layouts. The divide-by-zero error and subsequent OOPS condition create a predictable crash scenario that can be exploited to either cause system unavailability or potentially pave the way for more advanced exploitation techniques. This vulnerability particularly affects systems running Linux kernel versions prior to 2.6.38-rc6-git6, making it a significant concern for organizations maintaining older kernel versions.
The vulnerability aligns with CWE-129, which addresses insufficient validation of length of input buffers, and represents a specific instance of improper input validation in kernel space code. From an ATT&CK perspective, this vulnerability falls under the T1068 technique of Exploitation for Privilege Escalation, as local users can leverage this flaw to gain control over system resources through kernel-level manipulation. The issue also demonstrates characteristics of T1499, which involves the exploitation of system resource exhaustion or manipulation, as the divide-by-zero condition effectively consumes system resources and causes operational disruption.
Mitigation strategies for this vulnerability primarily involve updating to kernel versions 2.6.38-rc6-git6 or later, where the validation logic has been corrected to properly validate the VBLK size value before processing. System administrators should also implement partition table validation measures and monitor for unauthorized modifications to disk partition structures. Additional protective measures include disabling unnecessary partition table parsing capabilities where possible and implementing kernel security modules that can detect and prevent malformed partition table processing. The vulnerability highlights the critical importance of input validation in kernel space code and demonstrates how seemingly minor validation gaps can create significant operational risks for system stability and availability.