CVE-2026-98833 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
mtd: core: call _get_device() with the master MTD
__get_mtd_device() calls the master's _get_device() callback with mtd, which may be a partition. __put_mtd_device() passes the master.
This breaks gluebi partitions because gluebi_get_device() uses container_of() and therefore requires the master MTD. Pass the master to _get_device(), matching _put_device().
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Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel's Memory Technology Device subsystem contains a logical inconsistency in how device reference counting is handled for partitioned flash devices, specifically affecting gluebi partitions. The core issue stems from an asymmetry between the functions responsible for acquiring and releasing references to MTD devices. When __get_mtd_device() is invoked, it passes the specific mtd structure, which may represent a logical partition rather than the underlying physical device, to the master's _get_device callback. Conversely, when __put_mtd_device() is called during cleanup or release operations, it correctly passes the master MTD structure to the corresponding _put_device callback. This discrepancy creates a critical flaw in systems utilizing gluebi partitions, which rely on container_of macros to map from an mtd instance back to its parent device context.
Gluebi partitions are designed to present block devices over raw flash memory by leveraging this mapping mechanism. The container_of macro requires the pointer passed to it to be of the correct type and offset within the containing structure. Because __get_mtd_device() passes a partition-specific mtd object instead of the master MTD, gluebi_get_device receives an incorrect context. This leads to invalid memory access or logic errors when attempting to retrieve device information, potentially causing kernel panics, data corruption, or failure to initialize block devices properly. The vulnerability is classified as CWE-682 Incorrect Calculation and CWE-754 Improper Check for Unusual or Exceptional Conditions, reflecting the fundamental error in handling object references within a hierarchical device model.
From an operational perspective, this flaw impacts systems that depend on stable access to flash memory through block interfaces, such as embedded Linux devices using NAND or NOR flash storage. Attackers with local access could potentially trigger these code paths during partition enumeration or unmounting operations to induce denial of service conditions by crashing the kernel. While remote exploitation is unlikely due to the nature of MTD subsystem interactions typically requiring privileged access, the stability impact on critical infrastructure components remains significant. The vulnerability aligns with MITRE ATT&CK technique T1053 Scheduled Task/Job, as it involves system-level resource management routines that can be manipulated through legitimate administrative actions if triggered repeatedly or under specific timing conditions during device state transitions.
The resolution addresses this by ensuring consistency in the MTD reference counting mechanism. The fix modifies __get_mtd_device() to pass the master MTD structure to the _get_device callback, mirroring the behavior of __put_mtd_device(). This alignment guarantees that gluebi_get_device receives the expected context for container_of operations, thereby restoring correct device mapping and preventing invalid memory accesses. Administrators should apply kernel updates containing this patch immediately in environments relying on gluebi partitions or similar MTD partitioning schemes. Additionally, developers implementing custom MTD drivers must verify their _get_device implementations handle master versus partition contexts appropriately to maintain compatibility with the corrected core logic. Regular auditing of device driver reference counting patterns can prevent similar asymmetries in other subsystems where hierarchical object relationships are managed through callback interfaces.