CVE-2022-49693 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/msm/mdp4: Fix refcount leak in mdp4_modeset_init_intf
of_graph_get_remote_node() returns remote device node pointer with refcount incremented, we should use of_node_put() on it when not need anymore. Add missing of_node_put() to avoid refcount leak.
Patchwork: https://patchwork.freedesktop.org/patch/488473/
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 03/06/2025
The vulnerability identified as CVE-2022-49693 represents a memory management issue within the Linux kernel's display subsystem, specifically affecting the msm mdp4 driver component. This flaw manifests as a reference count leak in the mdp4_modeset_init_intf function where the of_graph_get_remote_node() API is utilized to retrieve remote device node pointers. The Linux kernel's device tree framework employs reference counting mechanisms to manage the lifecycle of device node objects, ensuring proper memory allocation and deallocation. When device tree nodes are accessed through various API functions, these functions typically increment reference counts to maintain object validity during use, but require corresponding decrement operations to release resources properly.
The technical implementation of this vulnerability stems from improper resource management within the display driver's initialization sequence. The of_graph_get_remote_node() function, which is part of the device tree graph API, returns a pointer to a remote device node with its reference count already incremented to reflect the caller's ownership of the reference. This pattern follows standard kernel memory management conventions where API functions that return references to objects must be paired with corresponding release functions to prevent resource leaks. However, in the mdp4_modeset_init_intf function, the code fails to call of_node_put() on the returned node pointer when the reference is no longer needed, resulting in a persistent reference count that prevents the underlying memory from being freed.
The operational impact of this reference count leak, while appearing minor in isolation, can accumulate over time and potentially lead to system resource exhaustion. In embedded systems or mobile devices that heavily utilize display drivers, such as smartphones and tablets running Linux-based operating systems, continuous memory leaks can gradually consume available system resources. The affected msm mdp4 driver is commonly found in Qualcomm Snapdragon processors and other mobile SoCs that implement the msm (Mobile Side Module) display subsystem. This vulnerability affects systems where the device tree configuration includes display graph connections that require remote node resolution, particularly in devices that support advanced display features such as multiple display outputs, dynamic refresh rates, or complex display pipeline configurations.
The fix implemented addresses this issue by adding the missing of_node_put() call to properly decrement the reference count when the remote node pointer is no longer required. This remediation follows established kernel development practices and aligns with the Linux kernel's device tree management guidelines. The fix demonstrates adherence to CWE-404, which specifically addresses improper resource management and memory leaks in software systems. From an attacker perspective, this vulnerability represents a denial of service vector that could potentially degrade system performance or cause memory exhaustion under sustained usage conditions, though it does not provide direct execution capabilities or privilege escalation paths.
Security considerations for this vulnerability extend beyond immediate resource consumption concerns to encompass broader system stability implications. The msm mdp4 driver operates within the kernel's graphics subsystem, making it a critical component for display functionality in mobile and embedded systems. Systems that rely heavily on display rendering, such as automotive infotainment systems, smart TVs, or industrial embedded devices, could experience degraded performance or instability due to the accumulating reference count leaks. The vulnerability's impact is particularly concerning in environments where display drivers are frequently initialized and reinitialized, such as during system boot processes, display mode changes, or when handling hotplug events for external displays. This issue underscores the importance of proper resource management in kernel drivers and highlights the need for comprehensive testing of device tree operations and reference counting mechanisms in graphics subsystems. The fix aligns with ATT&CK framework techniques related to system resource exhaustion and kernel memory management, representing a fundamental security practice that prevents resource leaks that could be exploited for denial of service attacks in resource-constrained environments.