CVE-2024-40970 is a vulnerability identified in the Linux kernel specifically related to the dw-axi-dmac (AXI DMA controller) driver. The issue arises from an overrun of the hw_desc array, which is used to manage hardware descriptors for DMA operations. In the described scenario, when the number of buffers (nr_buffers) is set to 3 and each descriptor consists of 3 segments, the total allocated DMA channel descriptors (descs_allocated) becomes 9. The function axi_desc_put() incorrectly handles the hw_desc array based on descs_allocated, leading to an out-of-bounds access and ultimately causing a kernel panic. This vulnerability is a classic buffer overrun issue within kernel memory management for DMA descriptors. The proposed fix involves adding a new member to the axi_dma_desc structure to track the exact number of allocated hw_descs and using this count in axi_desc_put() to prevent overruns. Additionally, the patch removes the call to axi_chan_start_first_queued() after transfer completion to avoid unbalanced states where started descriptors might be interrupted and transfers ignored due to the DMA channel not being enabled. This vulnerability can cause system instability and denial of service (DoS) through kernel panics triggered by malformed or unexpected DMA descriptor configurations. No known exploits are currently reported in the wild, and the vulnerability was published on July 12, 2024.

For European organizations, this vulnerability poses a risk primarily to systems running affected Linux kernel versions with the dw-axi-dmac driver enabled, which is common in embedded systems, industrial control devices, and certain server environments using AXI DMA controllers. Exploitation could lead to kernel panics causing system crashes and denial of service, impacting availability of critical infrastructure, manufacturing systems, or cloud services relying on affected Linux kernels. Confidentiality and integrity impacts are limited as the vulnerability does not directly allow code execution or privilege escalation, but repeated crashes could disrupt operations and lead to downtime. Organizations in sectors such as manufacturing, telecommunications, and cloud service providers in Europe that deploy Linux-based embedded or specialized hardware are particularly at risk. The lack of known exploits reduces immediate threat but patching is critical to prevent potential future exploitation or accidental triggering of the bug.

1. Apply the official Linux kernel patches addressing CVE-2024-40970 as soon as they become available from trusted sources or Linux distribution vendors. 2. For embedded or industrial systems using the dw-axi-dmac driver, verify kernel versions and update firmware or kernel images accordingly. 3. Conduct thorough testing of DMA-related subsystems after patching to ensure stability and correct descriptor handling. 4. Implement monitoring for kernel panics and system crashes related to DMA operations to detect potential exploitation or accidental triggers. 5. Limit access to systems running vulnerable kernels to trusted users and networks to reduce risk of malicious triggering. 6. For critical infrastructure, consider deploying redundant systems or failover mechanisms to maintain availability during patching or in case of crashes. 7. Engage with Linux distribution maintainers or vendors to confirm patch availability and backporting for long-term support kernels used in production environments.