CVE-2014-7283 in Linux
Summary
by MITRE
The xfs_da3_fixhashpath function in fs/xfs/xfs_da_btree.c in the xfs implementation in the Linux kernel before 3.14.2 does not properly compare btree hash values, which allows local users to cause a denial of service (filesystem corruption, and OOPS or panic) via operations on directories that have hash collisions, as demonstrated by rmdir operations.
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Analysis
by VulDB Data Team • 02/21/2022
The vulnerability identified as CVE-2014-7283 represents a critical flaw in the Linux kernel's XFS filesystem implementation that stems from improper handling of hash values within the directory allocation btree structure. This issue exists specifically within the xfs_da3_fixhashpath function located in fs/xfs/xfs_da_btree.c, where the kernel fails to correctly compare btree hash values during directory operations. The flaw manifests when hash collisions occur in directory structures, creating a scenario where the filesystem's internal data structures become corrupted due to inadequate validation of hash value comparisons.
The technical nature of this vulnerability places it squarely within the domain of software quality assurance and kernel-level security, classified under CWE-129 Input Validation and CWE-125 Out-of-bounds Read. The flaw exploits a condition where the xfs_da3_fixhashpath function does not properly validate hash values during btree traversal operations, leading to potential memory corruption when processing directories with hash collisions. This improper comparison mechanism allows local attackers to manipulate directory structures in a way that triggers kernel panics or system crashes, as the btree structure becomes corrupted during hash path fixing operations.
The operational impact of this vulnerability extends beyond simple denial of service to encompass potential filesystem corruption that could result in data loss or system instability. When local users perform operations such as rmdir on directories that contain hash collisions, the flawed hash comparison logic causes the kernel to follow incorrect btree paths, ultimately leading to kernel oops messages or system panics. This vulnerability affects systems running Linux kernel versions prior to 3.14.2, making it particularly relevant for organizations maintaining older kernel versions or those that have not yet applied the necessary security patches.
The exploitation of this vulnerability demonstrates a classic case of insufficient boundary checking in kernel space operations, aligning with ATT&CK technique T1068, which involves the exploitation of legitimate credentials and system privileges to gain unauthorized access to kernel-level resources. The attack vector requires local system access but does not necessitate elevated privileges, making it particularly dangerous in multi-user environments where users might be able to leverage this flaw to disrupt system operations. The impact of such an attack could be significant for enterprise environments relying on XFS filesystems, as it could lead to unauthorized service disruption and potential data integrity issues.
Mitigation strategies for this vulnerability should focus on immediate kernel version updates to 3.14.2 or later, which contain the necessary patches to fix the hash comparison logic in the xfs_da3_fixhashpath function. Organizations should also implement monitoring systems to detect unusual directory operations that might indicate attempted exploitation of this vulnerability. Additionally, security teams should consider implementing filesystem-level controls and access restrictions to limit local user capabilities that could lead to exploitation. The patch addresses the root cause by ensuring proper hash value comparison during btree path fixing operations, thereby preventing the corruption of directory structures that leads to system crashes.