CVE-2026-89824 in Linux
Summary
by MITRE • 09/16/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/panel-edp: fix i2c adapter leak on probe failure
Make sure to drop the i2c adapter reference on probe failure (e.g. probe deferral) and on driver unbind also if a devicetree redundantly uses the 'ddc-i2c-bus' property to point to the aux ddc bus.
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Analysis
by VulDB Data Team • 09/16/2026
The Linux kernel's Direct Rendering Manager subsystem, specifically within the panel-edp component responsible for managing embedded DisplayPort panels, contained a resource management flaw that resulted in an i2c adapter reference leak during specific driver lifecycle events. This vulnerability stems from improper handling of device tree properties when initializing hardware interfaces. The code path involved relies on retrieving references to i2c adapters associated with display data channels, commonly referred to as ddc-i2c-bus nodes within the system's device tree configuration. Under normal operational conditions where probe operations succeed immediately and without interruption, these resources are managed correctly. However, when a probe operation fails due to deferral or other transient errors, or during subsequent driver unbind procedures, the kernel failed to release the acquired reference count for the i2c adapter object.
This oversight constitutes an improper resource cleanup issue that aligns with CWE-401, which describes memory leaks and resource exhaustion resulting from failure to free allocated resources. In the context of Linux kernel development, every time a driver acquires a reference to a device or bus interface using functions such as i2c_get_adapter, it increments a refcount that must be decremented via i2c_put_adapter when the operation is complete or if an error occurs before successful initialization. The defect in panel-edp meant that on probe failure scenarios, particularly those involving probe deferral where the driver temporarily yields control to wait for dependencies, and during explicit unbind operations, this decrement step was omitted. This omission leaves the reference count artificially elevated, preventing the kernel from freeing or reusing the underlying i2c adapter structure even after it is no longer needed by the display subsystem.
The operational impact of this vulnerability manifests primarily as a gradual resource leak within the system's memory and device management structures. While a single instance might seem negligible in terms of immediate performance degradation, repeated occurrences can lead to significant consequences over time. As more probe failures or unbind events occur, potentially triggered by hot-plugging display devices, driver reloads, or system suspend-resume cycles that involve panel re-initialization, the accumulated leaked references consume kernel memory and hold onto hardware resources indefinitely. This behavior reduces the pool of available i2c adapters for other subsystems, potentially leading to resource exhaustion errors where new devices cannot be initialized because all adapter slots are effectively locked by unreleased references from previous failed attempts. Such conditions can degrade system stability and may eventually cause broader input-output failures across components relying on the same bus infrastructure.
From a threat modeling perspective, this issue is classified under ATT&CK technique T1074, specifically related to resource hijacking or local denial of service through exhaustion mechanisms if exploited repeatedly in an automated fashion. Although typically considered a low-severity bug due to its non-exploitable nature for remote code execution and the requirement for physical access or specific hardware interaction scenarios involving display panels, it represents a critical reliability flaw in kernel-space drivers. The vulnerability does not allow privilege escalation but undermines system integrity by depleting finite kernel resources. It highlights the importance of rigorous error handling paths in driver development, ensuring that every acquisition path has a corresponding release path regardless of success or failure outcomes during initialization sequences.
Mitigation strategies for this vulnerability involve applying the upstream Linux kernel patch that corrects the reference counting logic within the panel-edp driver code. System administrators and distribution maintainers should ensure their kernels are updated to versions containing this fix, which explicitly adds calls to drop i2c adapter references in both probe failure branches and unbind routines. For environments where immediate patching is not feasible, mitigating factors include minimizing unnecessary hot-plug events of embedded display panels during system operation and avoiding frequent driver reloads or module unbinding cycles that trigger the affected code paths repeatedly. Long-term remediation requires enforcing static analysis tools in kernel development pipelines to detect missing resource release patterns on error exit paths, thereby preventing similar CWE-401 instances across other subsystems before they reach production environments.