CVE-2024-42127 in Linux
Summary
by MITRE • 07/30/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/lima: fix shared irq handling on driver remove
lima uses a shared interrupt, so the interrupt handlers must be prepared to be called at any time. At driver removal time, the clocks are disabled early and the interrupts stay registered until the very end of the remove process due to the devm usage. This is potentially a bug as the interrupts access device registers which assumes clocks are enabled. A crash can be triggered by removing the driver in a kernel with CONFIG_DEBUG_SHIRQ enabled. This patch frees the interrupts at each lima device finishing callback so that the handlers are already unregistered by the time we fully disable clocks.
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Analysis
by VulDB Data Team • 10/06/2025
The vulnerability CVE-2024-42127 resides within the Linux kernel's direct rendering manager lima driver component which manages graphics processing units for certain embedded systems. This issue specifically affects the handling of shared interrupt requests during driver removal operations, creating a potential race condition that could lead to system instability. The lima driver utilizes shared interrupts, meaning multiple hardware components can trigger the same interrupt line, requiring careful management of interrupt handler registration and unregistration to prevent conflicts and ensure proper system operation. The flaw manifests when the driver is being unloaded from the kernel, particularly in configurations where CONFIG_DEBUG_SHIRQ is enabled, which provides additional debugging capabilities for shared interrupt handling but also exposes underlying race conditions.
The technical root cause stems from the improper sequencing of interrupt handler cleanup during the driver removal process. When the lima driver is removed, the system disables device clocks early in the process to conserve power and prevent further hardware activity. However, the interrupt handlers remain registered due to the use of devm (device managed) resources, which automatically handle cleanup but do not account for the timing requirements of shared interrupt handling. This creates a scenario where interrupt handlers might be invoked after clocks have been disabled, causing them to attempt access to device registers that are no longer functional. The interrupt handlers access hardware registers that require active clocks to be accessible, creating a direct dependency between interrupt processing and hardware state that is not properly managed during driver removal.
The operational impact of this vulnerability extends beyond simple system crashes, potentially affecting system stability and reliability in embedded graphics environments where the lima driver is utilized. When the driver removal process encounters this condition, particularly with debugging enabled, the system may experience kernel oops, memory corruption, or complete system lockups. This vulnerability is particularly concerning in production embedded systems where driver reloads or updates might occur, as the timing of interrupt handling during these operations could trigger the problematic code path. The issue demonstrates poor resource management practices in the driver's cleanup sequence, where the temporal dependency between hardware clock states and interrupt handler execution was not properly considered.
Mitigation strategies for this vulnerability involve implementing proper interrupt handler cleanup at the appropriate stage of the driver removal process. The fix addresses the issue by ensuring interrupts are freed at each lima device finishing callback rather than relying solely on the devm cleanup mechanism. This approach ensures that interrupt handlers are unregistered before clocks are fully disabled, eliminating the race condition that could cause handlers to access disabled hardware registers. This solution aligns with best practices for shared interrupt handling as outlined in the linux kernel documentation and follows the principle of proper resource ordering during system shutdown. The fix also demonstrates adherence to security principles that require proper resource management to prevent unintended system behavior, particularly in kernel space where improper handling can lead to system compromise. This vulnerability would typically be classified under CWE-691 as insufficient control flow management and could be mapped to ATT&CK technique T1059.001 for kernel-level code execution and system stability compromise.