CVE-2025-38659 in Linux
Summary
by MITRE • 08/22/2025
In the Linux kernel, the following vulnerability has been resolved:
gfs2: No more self recovery
When a node withdraws and it turns out that it is the only node that has the filesystem mounted, gfs2 currently tries to replay the local journal to bring the filesystem back into a consistent state. Not only is that a very bad idea, it has also never worked because gfs2_recover_func() will refuse to do anything during a withdraw.
However, before even getting to this point, gfs2_recover_func() dereferences sdp->sd_jdesc->jd_inode. This was a use-after-free before commit 04133b607a78 ("gfs2: Prevent double iput for journal on error") and is a NULL pointer dereference since then.
Simply get rid of self recovery to fix that.
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Analysis
by VulDB Data Team • 05/29/2026
The vulnerability described in CVE-2025-38659 affects the Linux kernel's gfs2 file system implementation, specifically addressing a critical flaw in the cluster file system's recovery mechanism. This issue manifests when a node in a gfs2 cluster withdraws from the system, creating a scenario where the node becomes the sole mount of the filesystem. The gfs2 subsystem attempts to recover the file system state by replaying the local journal, a process that fundamentally undermines the integrity and stability of the cluster environment.
The technical flaw stems from a problematic recovery procedure that attempts to execute gfs2_recover_func() during node withdrawal scenarios. This function contains a critical dereference operation that accesses sdp->sd_jdesc->jd_inode without proper validation, leading to either use-after-free conditions or null pointer dereferences depending on the kernel version. The vulnerability represents a fundamental design flaw where the system attempts to perform recovery operations that are not only logically flawed but also technically impossible to execute correctly, as the recovery function explicitly refuses to operate during withdrawal events.
The operational impact of this vulnerability is severe as it can lead to system instability, potential data corruption, and complete system crashes when gfs2 clusters encounter node withdrawal events. The recovery mechanism that was intended to maintain file system consistency actually creates a path to system failure, making the cluster environment more vulnerable than if no recovery attempt were made at all. This issue affects distributed computing environments that rely on gfs2 for shared storage access, potentially compromising the availability and reliability of critical infrastructure.
The fix for CVE-2025-38659 involves completely eliminating the self-recovery mechanism from the gfs2 implementation, which aligns with security best practices for preventing complex recovery logic that can introduce additional attack surfaces. This approach follows the principle of least privilege and reduces the attack surface by removing problematic code paths. The solution directly addresses the root cause by preventing the execution of recovery functions that cannot succeed, thereby eliminating both the use-after-free and null pointer dereference conditions. This remediation approach is consistent with the principle of fail-safe design where the system gracefully handles failure conditions rather than attempting complex recovery operations that may introduce additional vulnerabilities. The fix effectively prevents the scenario where a node withdrawal event could lead to system crashes or data corruption, ensuring that gfs2 clusters maintain stability even under adverse conditions. This vulnerability demonstrates the importance of careful design in distributed systems where recovery mechanisms must be thoroughly validated and tested under all possible failure scenarios to prevent introducing new security risks.