CVE-2026-68303 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/vc4: hvs/v3d: Fix null dereference in unbind
The hvs and v3d drivers use dev_get_drvdata(master) in their unbind functions. Since the vc4-drm gets removed before its dependent drivers (vc4_hvs/vc4_v3d) the vc4_hvs_unbind/vc4_v3d_unbind functions try to get drvdata of its master and fails with a null dereference error.
Use the data pointer passed to the unbind functions directly instead of dev_get_drvdata(master). This avoids using potentially freed memory.
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Analysis
by VulDB Data Team • 08/10/2026
This vulnerability exists within the Linux kernel's graphics subsystem, specifically affecting the vc4 display and video core drivers. The issue manifests as a null pointer dereference during driver unbinding operations when the vc4-drm device is removed before its dependent vc4_hvs and vc4_v3d drivers. The root cause lies in the improper use of dev_get_drvdata(master) within the unbind functions of these drivers, which attempts to access driver data that may have already been freed or invalidated during the device removal process.
The technical flaw occurs because the vc4_hvs_unbind and vc4_v3d_unbind functions rely on dev_get_drvdata(master) to retrieve driver-specific data associated with their master device. However, when the vc4-drm device undergoes removal, its dependent drivers are still in the process of being unbound, creating a race condition where the master device's driver data pointer becomes invalid or null. This scenario represents a classic use-after-free vulnerability pattern that can lead to system crashes or potentially exploitable conditions. The flaw directly maps to CWE-416, which addresses use after free conditions, and demonstrates poor resource management practices in kernel driver code.
The operational impact of this vulnerability extends beyond simple system instability, as it can result in complete system crashes or hangs during driver unbinding operations. When the graphics subsystem attempts to clean up resources during system shutdown or driver reload scenarios, the null pointer dereference causes immediate kernel oops or panic conditions. This affects any system running Linux kernels with vc4 graphics support, particularly those using Raspberry Pi or other embedded systems that rely on this graphics architecture. The vulnerability is especially concerning in embedded environments where system reliability is paramount and unexpected crashes can lead to complete system failures.
The recommended mitigation involves modifying the unbind functions to utilize the data pointer that is directly passed to these functions rather than attempting to retrieve driver data through dev_get_drvdata(master). This approach eliminates the dependency on potentially freed memory structures and ensures that valid driver state information remains accessible during cleanup operations. The fix aligns with established kernel development best practices for driver unbinding operations, where function parameters should be preferred over indirect data retrieval mechanisms that may access invalidated memory. This solution prevents the use of freed memory while maintaining proper driver state management throughout the unbinding process and demonstrates adherence to secure coding principles outlined in various kernel security guidelines and ATT&CK framework considerations for kernel-level vulnerabilities.