CVE-2023-54255 in Linux
Summary
by MITRE • 12/30/2025
In the Linux kernel, the following vulnerability has been resolved:
sh: dma: Fix DMA channel offset calculation
Various SoCs of the SH3, SH4 and SH4A family, which use this driver, feature a differing number of DMA channels, which can be distributed between up to two DMAC modules. The existing implementation fails to correctly accommodate for all those variations, resulting in wrong channel offset calculations and leading to kernel panics.
Rewrite dma_base_addr() in order to properly calculate channel offsets in a DMAC module. Fix dmaor_read_reg() and dmaor_write_reg(), so that the correct DMAC module base is selected for the DMAOR register.
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Analysis
by VulDB Data Team • 04/27/2026
The vulnerability identified as CVE-2023-54255 represents a critical flaw in the Linux kernel's SH (SuperH) architecture DMA driver implementation. This issue affects embedded systems utilizing SH3, SH4, and SH4A processor families that employ DMA controllers with varying channel configurations across different device models. The fundamental problem stems from incorrect channel offset calculations within the Direct Memory Access controller driver, which directly impacts system stability and reliability. The vulnerability manifests when the kernel attempts to manage DMA operations on hardware platforms where the number of available DMA channels differs between DMAC modules, creating a mismatch between expected and actual memory addressing.
The technical root cause lies in the improper implementation of the dma_base_addr() function and related register access methods within the SH DMA driver subsystem. Specifically, the existing code fails to correctly account for the variable number of DMA channels distributed across up to two DMAC modules present in different SoC implementations. This miscalculation affects the dmaor_read_reg() and dmaor_write_reg() functions which are responsible for accessing the DMAOR (DMA Operation Register) that controls DMA channel operations. The incorrect base address calculation leads to memory access violations when the kernel attempts to program DMA channels, particularly when operating across multiple DMAC modules with different channel counts.
The operational impact of this vulnerability is severe, as it can result in immediate system crashes and kernel panics during DMA operations. When the kernel encounters a DMA channel that falls outside the calculated offset range, the system becomes unstable and typically requires a complete reboot to recover. This affects embedded systems running Linux that utilize the SH architecture, particularly those in industrial control systems, automotive applications, and networking equipment where reliable DMA operations are essential for proper system function. The vulnerability is particularly concerning in real-time embedded environments where system reliability and deterministic behavior are paramount for safety and operational requirements.
The fix implemented addresses the core calculation errors by rewriting the dma_base_addr() function to properly handle the channel offset calculations within DMAC modules. This correction ensures that each DMA channel is correctly mapped to its respective base address regardless of the number of channels available in each DMAC module. Additionally, the dmaor_read_reg() and dmaor_write_reg() functions have been modified to select the correct DMAC module base address when accessing the DMAOR register, preventing cross-module memory access errors. This remediation aligns with the CWE-129 principle of ensuring proper input validation and bounds checking in memory operations, while also addressing potential ATT&CK techniques related to privilege escalation through kernel exploitation. The fix maintains backward compatibility while extending support for the full range of SH architecture SoC variations, ensuring that DMA operations function correctly across all supported hardware platforms without causing system instability.