CVE-2024-57892 in Linux
Summary
by MITRE • 01/15/2025
In the Linux kernel, the following vulnerability has been resolved:
ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv
When mounting ocfs2 and then remounting it as read-only, a slab-use-after-free occurs after the user uses a syscall to quota_getnextquota. Specifically, sb_dqinfo(sb, type)->dqi_priv is the dangling pointer.
During the remounting process, the pointer dqi_priv is freed but is never set as null leaving it to be accessed. Additionally, the read-only option for remounting sets the DQUOT_SUSPENDED flag instead of setting the DQUOT_USAGE_ENABLED flags. Moreover, later in the process of getting the next quota, the function ocfs2_get_next_id is called and only checks the quota usage flags and not the quota suspended flags.
To fix this, I set dqi_priv to null when it is freed after remounting with read-only and put a check for DQUOT_SUSPENDED in ocfs2_get_next_id.
[[email protected]: coding-style cleanups]
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 03/09/2026
The vulnerability described in CVE-2024-57892 represents a critical use-after-free condition within the Oracle Cluster File System 2 (OCFS2) implementation in the Linux kernel. This flaw manifests specifically during the mount and remount operations of OCFS2 filesystems, creating a scenario where memory corruption can occur through improper pointer management. The issue stems from a fundamental failure in the quota subsystem's memory lifecycle management, where a dangling pointer reference persists after memory deallocation, leading to unpredictable behavior and potential security exploits.
The technical root cause involves the improper handling of the dqi_priv pointer within the quota information structure during remount operations. When an OCFS2 filesystem is remounted as read-only, the system frees the memory associated with dqi_priv but fails to nullify the pointer reference, leaving it in a dangling state. This pointer continues to reference freed memory locations, creating a classic use-after-free vulnerability that can be exploited by malicious actors to gain unauthorized access or cause system instability. The flaw is particularly insidious because it only manifests during specific operational sequences involving quota operations and remounting, making detection challenging in production environments.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially compromise the integrity of the entire filesystem quota management system. When the quota_getnextquota syscall is invoked after the problematic remount operation, the ocfs2_get_next_id function attempts to access the freed dqi_priv pointer without proper validation. The function's insufficient flag checking logic fails to account for the DQUOT_SUSPENDED state, which should prevent quota operations during certain filesystem states. This creates a dangerous race condition where memory access occurs before proper state validation, potentially allowing attackers to execute arbitrary code or cause denial of service conditions that could affect cluster-wide filesystem operations.
The fix implemented addresses both the immediate pointer management issue and the broader validation logic gap in the quota subsystem. Setting dqi_priv to null after freeing it ensures that subsequent accesses will either fail gracefully or trigger proper error handling rather than causing memory corruption. Additionally, adding the DQUOT_SUSPENDED flag check in ocfs2_get_next_id provides proper state validation before allowing quota operations, aligning with security best practices for resource management. This remediation follows established patterns for preventing use-after-free vulnerabilities and demonstrates adherence to secure coding principles that prevent dangling pointer access. The solution effectively closes the security gap while maintaining the intended functionality of the OCFS2 filesystem's quota management capabilities.
This vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software implementations, and represents a clear violation of proper memory management practices. From an ATT&CK perspective, this flaw could enable privilege escalation and persistence mechanisms through filesystem manipulation, making it particularly concerning for enterprise environments that rely on clustered storage solutions. The vulnerability's impact is amplified in high-availability systems where OCFS2 is commonly deployed, as it could potentially compromise entire cluster operations. The fix demonstrates proper defensive programming techniques that should be applied across similar filesystem implementations to prevent similar issues in the broader Linux kernel ecosystem.