CVE-2023-52760 in Linux
Summary
by MITRE • 05/21/2024
In the Linux kernel, the following vulnerability has been resolved:
gfs2: Fix slab-use-after-free in gfs2_qd_dealloc
In gfs2_put_super(), whether withdrawn or not, the quota should be cleaned up by gfs2_quota_cleanup().
Otherwise, struct gfs2_sbd will be freed before gfs2_qd_dealloc (rcu callback) has run for all gfs2_quota_data objects, resulting in use-after-free.
Also, gfs2_destroy_threads() and gfs2_quota_cleanup() is already called by gfs2_make_fs_ro(), so in gfs2_put_super(), after calling gfs2_make_fs_ro(), there is no need to call them again.
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Analysis
by VulDB Data Team • 08/07/2026
The vulnerability CVE-2023-52760 represents a critical use-after-free condition within the Linux kernel's GFS2 (Global File System 2) implementation that stems from improper resource cleanup during filesystem unmount operations. This flaw exists in the gfs2_put_super() function where the quota cleanup process fails to properly handle the lifecycle of quota data structures, creating a scenario where memory objects are accessed after being freed. The issue manifests when the gfs2_sbd structure is deallocated before all associated gfs2_quota_data objects have completed their RCU (Read-Copy-Update) callback processing through gfs2_qd_dealloc, leading to potential memory corruption and system instability.
The technical root cause of this vulnerability lies in the improper sequencing of cleanup operations within the GFS2 filesystem driver. When gfs2_put_super() is invoked during filesystem unmount, the function fails to ensure that gfs2_quota_cleanup() is called consistently regardless of whether quotas have been withdrawn. This oversight results in a race condition where the gfs2_sbd structure containing references to quota data objects gets freed prematurely, while the RCU callbacks for gfs2_qd_dealloc are still pending execution. The flaw specifically affects the memory management of quota data structures, where the kernel's reference counting mechanism fails to prevent access to freed memory regions. According to CWE-416, this represents a classic use-after-free vulnerability that can lead to arbitrary code execution or system crashes, while the ATT&CK technique T1059.008 covers the potential for command execution through memory corruption.
The operational impact of this vulnerability extends beyond simple system instability to potentially enable privilege escalation and denial-of-service conditions within systems utilizing GFS2 filesystems. When exploited, the use-after-free condition could allow malicious actors to manipulate memory contents, potentially leading to kernel memory corruption that might be leveraged for privilege escalation attacks. Systems running GFS2 filesystems, particularly those in enterprise environments where shared storage is common, face elevated risk as the vulnerability can be triggered through normal filesystem unmount operations. The vulnerability affects kernel versions where the GFS2 filesystem implementation lacks proper synchronization between the main superblock cleanup and the quota data cleanup processes. The improper cleanup sequence creates a window where freed memory structures remain accessible to subsequent operations, making this vulnerability particularly dangerous in multi-threaded environments where memory corruption can propagate through the kernel's memory management subsystem.
Mitigation strategies for CVE-2023-52760 focus on ensuring proper resource cleanup ordering and implementing defensive programming practices within the kernel's GFS2 implementation. The recommended fix involves modifying gfs2_put_super() to always invoke gfs2_quota_cleanup() regardless of quota withdrawal status, ensuring that all quota data objects are properly cleaned up before the gfs2_sbd structure is freed. Additionally, the function should avoid redundant calls to gfs2_destroy_threads() and gfs2_quota_cleanup() by checking if gfs2_make_fs_ro() has already been executed, as these cleanup functions are already invoked during the read-only transition process. System administrators should prioritize applying kernel updates that contain the patched GFS2 implementation, while monitoring for any unusual system behavior that might indicate memory corruption. The fix aligns with security best practices for kernel memory management and follows the principle of least privilege by ensuring proper resource lifecycle management. Organizations using GFS2 filesystems should also implement monitoring for filesystem unmount operations and consider implementing additional security controls to prevent unauthorized access to systems where this vulnerability might be exploited.