CVE-2014-5472 in Linux
Summary
by MITRE
The parse_rock_ridge_inode_internal function in fs/isofs/rock.c in the Linux kernel through 3.16.1 allows local users to cause a denial of service (unkillable mount process) via a crafted iso9660 image with a self-referential CL entry.
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Analysis
by VulDB Data Team • 02/11/2022
The vulnerability described in CVE-2014-5472 resides within the Linux kernel's iso9660 filesystem implementation, specifically in the parse_rock_ridge_inode_internal function located in fs/isofs/rock.c. This flaw represents a classic case of infinite loop exploitation that can be leveraged by local attackers to disrupt system operations. The issue manifests when processing iso9660 images that contain self-referential CL (Child Link) entries, which are part of the Rock Ridge extensions used to provide POSIX file attributes on iso9660 filesystems. The vulnerability is particularly concerning because it can render the mount process unkillable, effectively causing a denial of service condition that impacts system availability.
The technical root cause of this vulnerability stems from inadequate input validation and loop termination logic within the filesystem parsing routine. When the kernel encounters a self-referential CL entry in an iso9660 image, the parse_rock_ridge_inode_internal function enters an infinite recursive loop as it attempts to resolve the circular reference. This occurs because the function does not properly detect when it is processing a self-referential entry and continues to traverse the same path repeatedly. The CWE-835 classification applies here as this represents an infinite loop vulnerability where the loop condition cannot be satisfied, leading to resource exhaustion and system instability. The flaw exists in the kernel's filesystem layer, specifically affecting the iso9660 implementation that is commonly used for optical media and disk image files.
From an operational impact perspective, this vulnerability allows local users to trigger a denial of service condition that can severely impact system stability and availability. The mount process becomes unkillable, meaning standard process termination mechanisms fail to work, forcing administrators to resort to system reboots to restore normal operations. This type of vulnerability is particularly dangerous in multi-user environments where local users could exploit it to disrupt services, or in systems where automated mounting processes are in place. The ATT&CK technique T1499.004 (Resource Hijacking) applies here as the vulnerability enables an attacker to consume system resources indefinitely. Additionally, this vulnerability could be leveraged in conjunction with other attacks to create persistent denial of service conditions that are difficult to detect and remediate.
Mitigation strategies for CVE-2014-5472 focus on both immediate patching and operational controls. The primary solution involves applying kernel updates that contain the fix for the infinite loop condition in the parse_rock_ridge_inode_internal function. The Linux kernel version 3.16.2 and subsequent releases contain the necessary patches that properly detect and handle self-referential CL entries. Organizations should prioritize patching systems running vulnerable kernel versions, particularly those that process untrusted iso9660 images. Operational mitigations include implementing strict file validation policies for iso9660 images, disabling automatic mounting of optical media, and monitoring for unusual mount process behavior. Network segmentation and privilege separation can also reduce the attack surface, as local access is required to exploit this vulnerability. The vulnerability also highlights the importance of proper input validation in kernel space code, as similar issues could exist in other filesystem implementations and emphasizes the need for comprehensive testing of edge cases in filesystem parsing routines.