CVE-2025-37740 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
jfs: add sanity check for agwidth in dbMount
The width in dmapctl of the AG is zero, it trigger a divide error when calculating the control page level in dbAllocAG.
To avoid this issue, add a check for agwidth in dbAllocAG.
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Analysis
by VulDB Data Team • 03/15/2026
The vulnerability identified as CVE-2025-37740 resides within the Linux kernel's JFS (Journaled File System) implementation, specifically affecting the database mount and allocation processes. This issue manifests during the initialization of JFS filesystems where the system attempts to calculate control page levels for allocation groups. The flaw occurs when the allocation group width parameter in the dmapctl structure equals zero, creating a critical divide-by-zero condition that can lead to system instability or denial of service. The vulnerability represents a classic software error that can be exploited to disrupt normal system operations, particularly in environments where JFS is actively used for file storage management.
The technical root cause of this vulnerability stems from inadequate input validation within the dbAllocAG function, which is responsible for allocating space within allocation groups of the JFS filesystem. When the agwidth parameter in the dmapctl structure is improperly initialized or set to zero, the subsequent calculation of control page levels triggers a division operation by zero, causing the kernel to crash or become unresponsive. This type of error falls under the category of improper input validation and can be classified as CWE-369, which specifically addresses divide-by-zero conditions. The flaw demonstrates poor defensive programming practices where essential boundary checks are omitted, allowing malformed data to propagate through the system and cause critical failures.
The operational impact of this vulnerability extends beyond simple system crashes, as it can potentially lead to complete filesystem unavailability and data access disruption in affected systems. When a divide-by-zero error occurs in kernel space, it typically results in a kernel panic or system lockup, requiring manual intervention and system reboot to restore normal operations. This vulnerability affects systems running Linux kernels that include the JFS filesystem implementation, particularly those managing large storage volumes where allocation groups are actively utilized. The risk is elevated in high-availability environments where filesystem stability is paramount, as this flaw could be exploited to create denial of service conditions that impact business-critical applications relying on JFS storage.
The mitigation strategy for this vulnerability involves implementing proper input validation checks within the dbAllocAG function to ensure that agwidth parameters are never zero before performing any division operations. This fix aligns with the principle of defensive programming and follows the ATT&CK technique T1489 which addresses denial of service through system resource manipulation. The solution requires adding a sanity check that validates the agwidth parameter before proceeding with control page level calculations, ensuring that division operations are only performed when the divisor is non-zero. This approach prevents the kernel from entering an undefined state and maintains system stability even when encountering malformed allocation group parameters. System administrators should prioritize applying this patch to all affected systems, particularly those running JFS filesystems in production environments where continuous availability is required. The fix also serves as a reminder of the importance of input validation in kernel space operations and demonstrates how seemingly simple validation checks can prevent catastrophic system failures.