Linux Kernel VC4 DRM IRQ Handling Vulnerability

A vulnerability exists in the Linux kernel's VC4 Direct Rendering Manager (DRM) module related to improper handling of interrupt requests. The issue arises in the HDMI hotplug initialization function, where the platform_get_irq_byname() function is used to retrieve IRQ numbers for hotplug events. If this function encounters an error, it returns a negative value, which should be checked before proceeding. However, the current implementation directly passes the IRQ number to devm_request_threaded_irq() without verifying if the retrieval was successful. This oversight could lead to unhandled errors and potential instability.

Impact

The vulnerability could cause issues in interrupt handling, particularly for HDMI hotplug events, which may lead to improper management of connected displays.

Reproduction

The vulnerability can be reproduced by loading a Linux kernel with the VC4 DRM module active, particularly on Raspberry Pi devices. The HDMI hotplug initialization will incorrectly assume that IRQs have been successfully retrieved, potentially leading to missed hotplug events or improper handling of connected displays.

Remediation

Users can apply the latest patches from the Linux kernel stable tree, which include the necessary checks for IRQ retrieval errors before requesting threaded IRQs. These patches are available in the Linux Git repository.