CVE-2024-49956 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
gfs2: fix double destroy_workqueue error
When gfs2_fill_super() fails, destroy_workqueue() is called within gfs2_gl_hash_clear(), and the subsequent code path calls destroy_workqueue() on the same work queue again.
This issue can be fixed by setting the work queue pointer to NULL after the first destroy_workqueue() call and checking for a NULL pointer before attempting to destroy the work queue again.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 03/21/2026
The vulnerability identified as CVE-2024-49956 represents a critical double free error in the Linux kernel's gfs2 file system implementation that stems from improper work queue management during superblock initialization failures. This flaw occurs within the gfs2_fill_super() function where the system attempts to initialize the gfs2 file system but encounters an error condition that triggers the destruction of a work queue. The issue manifests when gfs2_gl_hash_clear() is invoked as part of the error handling path, leading to the first call to destroy_workqueue() on a work queue that has already been partially deallocated or is in an inconsistent state.
The technical implementation flaw arises from a lack of proper pointer validation and state management within the kernel's file system subsystem. When the gfs2_fill_super() function fails to complete initialization successfully, the code path continues through gfs2_gl_hash_clear() which calls destroy_workqueue() on a work queue that may not be in a valid state for a second destruction attempt. This pattern violates fundamental kernel safety principles and creates an opportunity for undefined behavior that can lead to system instability or potential privilege escalation.
The operational impact of this vulnerability extends beyond simple system crashes to potentially enable more sophisticated attack vectors. When a work queue is destroyed twice, the kernel's memory management subsystem may experience memory corruption, double-free conditions, or other heap-related issues that could be exploited by malicious actors to gain elevated privileges. The vulnerability specifically affects systems running the gfs2 file system where concurrent access to shared resources through work queues is common, making it particularly dangerous in enterprise environments where gfs2 is used for clustered file systems. This type of error commonly maps to CWE-459, which describes incomplete cleanup issues in software, and can be correlated with ATT&CK technique T1068, which involves exploiting vulnerabilities to execute code with elevated privileges.
The fix for this vulnerability requires implementing proper pointer management and defensive programming practices within the kernel code. The recommended solution involves setting the work queue pointer to NULL immediately after the first destroy_workqueue() call, followed by a NULL pointer check before any subsequent destruction attempts. This approach ensures that the work queue is only destroyed once, preventing the double-free condition that leads to memory corruption and system instability. The mitigation strategy aligns with best practices for kernel memory management and follows established patterns for handling resource cleanup in concurrent systems. This fix addresses the root cause by ensuring proper state tracking and preventing the reuse of already-destroyed kernel objects, which is essential for maintaining the integrity of the kernel's memory management subsystem and preventing potential exploitation scenarios that could compromise system security.