CVE-2021-47161 in Linux
Summary
by MITRE • 03/25/2024
In the Linux kernel, the following vulnerability has been resolved:
spi: spi-fsl-dspi: Fix a resource leak in an error handling path
'dspi_request_dma()' should be undone by a 'dspi_release_dma()' call in the error handling path of the probe function, as already done in the remove function
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Analysis
by VulDB Data Team • 08/04/2025
The vulnerability identified as CVE-2021-47161 represents a resource leak in the Freescale DSPI (DesignWare SPI) driver within the Linux kernel. This issue specifically affects the spi-fsl-dspi driver which manages SPI communication for Freescale processors. The flaw occurs in the error handling path of the probe function where DMA (Direct Memory Access) resources are not properly released when errors occur during driver initialization. This represents a classic resource management oversight that can lead to system instability and potential denial of service conditions.
The technical flaw stems from an inconsistent approach to resource management between the probe and remove functions of the spi-fsl-dspi driver. While the remove function correctly implements the dspi_release_dma() call to free DMA resources, the probe function fails to perform this cleanup operation during error conditions. When the dspi_request_dma() function successfully allocates DMA resources but subsequent initialization steps fail, the driver does not call dspi_release_dma() to undo the allocation, resulting in leaked DMA resources. This pattern violates fundamental resource management principles and creates a persistent resource exhaustion scenario.
The operational impact of this vulnerability extends beyond simple resource waste to potentially compromise system stability and availability. When multiple driver probe operations fail due to this resource leak, accumulated unreleased DMA resources can consume significant system memory and DMA channel capacity. This can lead to system slowdowns, application failures, or complete system hangs when the system runs out of available DMA resources. The vulnerability affects embedded systems and devices that rely heavily on SPI communication, particularly those using Freescale processors where the DSPI driver is actively utilized. The resource leak becomes more pronounced in systems with frequent driver initialization attempts or high SPI activity, amplifying the potential for service disruption.
Mitigation strategies for this vulnerability involve applying the official kernel patch that ensures consistent resource management between the probe and remove functions. System administrators should prioritize updating to kernel versions that include the fix, particularly in production environments where stability is critical. The patch implementation follows established security practices by ensuring that all resource allocation operations have corresponding deallocation calls in error handling paths, preventing resource leaks as defined by CWE-404. Organizations should also implement monitoring for unusual DMA resource consumption patterns that could indicate the presence of this vulnerability. Additionally, the fix aligns with ATT&CK framework considerations for system stability and resource management, addressing a fundamental infrastructure weakness that could be exploited to degrade system performance or availability. Regular kernel updates and vulnerability assessments remain essential practices to maintain system security posture against similar resource management flaws.