Hello LinuxPatch readers! Today, we're delving into a significant but manageable security concern that has emerged in the Linux ecosystem. Identified as CVE-2024-40970, this vulnerability affects the Linux kernel's handling of DMA (Direct Memory Access) transfers, specifically within the dw-axi-dmac driver component. With a CVSS (Common Vulnerability Scoring System) score of 5.5, it's classified with medium severity.
The specific function in question is how the hardware descriptor array (hw_desc) is managed. An array overrun issue was discovered, potentially leading to undesirable outcomes like kernel panic, where the system becomes unresponsive or crashes entirely. Let’s unpack the details of this vulnerability, how it affects your systems, and what measures have been proposed to mitigate the risk.
Before diving into the technicalities of the vulnerability, let’s understand the broader context. Direct Memory Access (DMA) is a capability in computing that allows hardware subsystems to access main system memory independently of the central processing unit (CPU). This process is crucial for high-speed data transfer in various applications, from network communications to video streaming.
The dw-axi-dmac driver, a component of the Linux kernel, facilitates these DMA operations. It manages data transfers by coordinating directly with hardware to push or pull data without overburdening the CPU. Therefore, any malfunction or bug in this driver could potentially compromise the transfer integrity or, worse, the stability of the entire system.
In instances where a certain number of buffer segments are configured - specifically, a scenario described in the vulnerability report where three buffers are each composed of three segments - the system may allocate a total of nine descriptors. This setup leads to the dw-axi-dmac driver's mechanism to exceed the configured limits of the hardware descriptor array, resulting in an array overrun. The overflow is not merely a benign error but critical enough to cause a kernel panic, compromising system stability and security.
To address CVE-2024-40970, a workaround involving structural changes to the axi_dma_desc structure has been suggested. The proposal consists of adding a new member to track the number of allocated hardware descriptors more accurately, thus preventing the hw_desc array from being overrun during operations. This architectural adjustment not only aims to solve the current overflow issue but also enhances the robustness of the descriptor management process.
Additionally, it has been proposed to eliminate the call to axi_chan_start_first_queued() following a transfer completion. This change is intended to prevent potential imbalances that can disrupt the DMA operations, thereby improving the overall reliability of the dw-axi-dmac driver during high-load conditions.
The impact of CVE-2024-40970, though medium in severity, underscores the critical nature of accurate hardware interaction within the kernel. For Linux users, especially those running systems with high data throughput requirements, it's essential to apply patches and updates that include these fixes. Keeping your system's kernel up-to-date ensures that such vulnerabilities are addressed promptly, maintaining system integrity and security.
As always, stay vigilant and ensure your systems are protected by regularly applying the latest patches and updates from trusted sources. If you’re using LinuxPatch services, rest assured that we’re on top of these updates, helping to safeguard your infrastructure against threats like CVE-2024-40970.
Until next time, stay secure and keep your systems patched!