CVE-2026-98386 in Linux
Summary
by MITRE • 10/14/2026
In the Linux kernel, the following vulnerability has been resolved:
scsi: qla2xxx: Use memset_io() to clear QLAFX00 request ring slot
For QLAFX00 the request ring is ioremapped device I/O memory (ha->iobase + req_que_off), not DMA-coherent RAM, which is why the rest of the FX00 path accesses it through memcpy_toio() and the wrt_reg_* helpers. __qla2x00_alloc_iocbs() however zeroed the producer slot with a plain memset(). On architectures such as ARM64 a regular memset() may emit unaligned or block-zeroing instructions (e.g. DC ZVA) that are invalid on Device memory, leading to a synchronous external abort.
Use memset_io() to clear the slot for QLAFX00, matching the I/O accessors used elsewhere on this ring. Other adapters keep the plain memset() on their DMA-coherent rings. The zero-fill is retained for FX00 because its IOCB builders (e.g. qlafx00_fxdisc_iocb()) copy only part of the entry and rely on the unused tail being pre-zeroed.
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Analysis
by VulDB Data Team • 10/14/2026
The Linux kernel driver for QLogic QLAFX00 Fibre Channel adapters contained a critical memory access flaw within its request ring management logic, specifically in the __qla2x00_alloc_iocbs function. This vulnerability stems from an incorrect assumption regarding the nature of the hardware memory interface used by this specific adapter family. The request ring for the QLAFX00 is mapped as device I/O memory rather than standard system RAM or DMA-coherent memory. In Linux kernel development, accessing device registers and I/O ports requires specialized accessors that ensure proper ordering, alignment, and instruction selection appropriate for hardware interfaces. While other parts of the FX00 driver correctly utilized ioremapped access functions such as memcpy_toio() and specific write register helpers to interact with this ring, the allocation routine erroneously employed a standard memset() call to zero out producer slots. This inconsistency created a divergence in how memory was accessed depending on which code path executed first or concurrently, leading to potential instability under certain conditions.
The technical severity of this flaw is most pronounced on architectures like ARM64, where the implementation of plain memset() often optimizes for performance by emitting block-zeroing instructions such as Data Cache Zero Asynchronous (DC ZVA) or similar bulk operations designed for coherent RAM. These instructions are fundamentally invalid when applied to device memory regions because they bypass the necessary bus transactions and barriers required to communicate with hardware peripherals. When a DC ZVA instruction is executed against an ioremapped address, it does not perform the intended write operation but instead triggers a synchronous external abort at the processor level. This results in a kernel panic or system crash, effectively denying service to any host relying on this storage adapter for I/O operations. The vulnerability represents a classic case of improper abstraction layer usage where software assumes memory properties that do not exist in hardware-specific contexts.
From a classification perspective, this issue aligns with CWE-681, which covers Incorrect Conversion between Numeric and Non-Numeric Types, specifically regarding the misuse of generic memory manipulation functions on specialized I/O regions. It also relates to CWE-457, Use of Uninitialized Variable, insofar as relying on memset for zeroing is a defensive programming practice that fails when the underlying mechanism does not function as expected due to architectural constraints. In terms of attack vectors and operational impact, this vulnerability primarily affects system stability rather than providing an avenue for privilege escalation or data exfiltration by external attackers. However, it can be triggered locally through normal driver operation, making it a reliability issue that could lead to Denial of Service conditions in production environments running ARM64-based servers with QLogic FX00 adapters. The ATT&CK framework does not have a direct mapping for this type of kernel bug as it is not an exploit technique but rather a defect; however, the resulting system crash would fall under T1529 System Shutdown or Reboot if exploited in a scenario where timing allows triggering the abort during critical operations.
The resolution involves replacing the standard memset() call with memset_io(), which is the correct accessor for writing to device memory mapped via ioremap. This function ensures that the zeroing operation uses instructions compatible with the hardware interface, preventing the generation of invalid bus cycles or cache maintenance commands on non-coherent regions. It is important to note that this fix is specific to the QLAFX00 path; other adapters utilizing DMA-coherent RAM continue to use plain memset() because it operates correctly and efficiently in those contexts. The zero-fill remains necessary for FX00 devices because their IOCB builders, such as qlafx00_fxdisc_iocb(), only copy a portion of the entry structure into hardware registers. They rely on the remaining unused tail bytes being pre-zeroed to ensure that undefined or stale data does not interfere with subsequent operations or cause misinterpretation by the firmware.
Mitigation for this vulnerability requires updating the Linux kernel to a version where the qla2xxx driver patch is applied. For systems unable to update immediately, disabling the use of QLAFX00 adapters in ARM64 environments may prevent triggering the abort condition until an upgrade can be scheduled. Administrators should monitor system logs for synchronous external aborts associated with scsi or qla2xxx modules as indicators that this code path has been executed on affected hardware configurations. Long-term, developers must adhere to strict adherence to I/O accessor APIs when dealing with ioremapped memory regions across all architectures to prevent similar architectural mismatches in future kernel versions.