CVE-2022-48663 in Linux
Summary
by MITRE • 04/28/2024
In the Linux kernel, the following vulnerability has been resolved:
gpio: mockup: fix NULL pointer dereference when removing debugfs
We now remove the device's debugfs entries when unbinding the driver. This now causes a NULL-pointer dereference on module exit because the platform devices are unregistered *after* the global debugfs directory has been recursively removed. Fix it by unregistering the devices first.
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Analysis
by VulDB Data Team • 04/28/2024
The vulnerability CVE-2022-48663 represents a critical null pointer dereference issue within the Linux kernel's gpio mockup driver implementation. This flaw manifests during module cleanup operations when the kernel attempts to remove debugfs entries associated with gpio mockup platform devices. The root cause stems from an improper ordering of cleanup operations within the driver's unbinding process, creating a temporal dependency that leads to system instability. The vulnerability specifically affects systems utilizing the gpio mockup driver for testing and development purposes, where the driver creates mock gpio devices to simulate hardware behavior without actual physical gpio pins.
The technical implementation of this vulnerability occurs in the gpio mockup driver's debugfs management subsystem. When the module is unloaded or the driver is unbound from platform devices, the kernel attempts to clean up debugfs entries that were created during device initialization. However, the current implementation fails to properly sequence the cleanup operations, resulting in a situation where global debugfs directories are recursively removed before individual platform device debugfs entries are properly unregistered. This creates a scenario where subsequent dereference operations on null pointers occur, leading to kernel panic conditions and system crashes. The flaw directly violates proper resource management principles and demonstrates inadequate handling of interdependent cleanup dependencies within the kernel's device model.
The operational impact of CVE-2022-48663 extends beyond simple system crashes to encompass potential denial of service conditions in embedded systems and development environments that rely on gpio mockup drivers. Systems utilizing gpio mockup functionality for hardware abstraction testing, virtualization environments, or development workflows may experience unexpected kernel panics during module unloading or system shutdown procedures. This vulnerability particularly affects kernel versions where the gpio mockup driver is compiled as a loadable module, creating a window of opportunity for exploitation during normal system maintenance operations. The issue represents a classic case of improper resource cleanup ordering that can lead to system instability in production environments where gpio mockup functionality is actively used.
Mitigation strategies for CVE-2022-48663 focus on implementing proper cleanup sequencing within the gpio mockup driver's unbinding routine. The fix requires reordering the cleanup operations to ensure platform devices are unregistered before the global debugfs directory structure is removed recursively. This approach aligns with established kernel development practices and follows the principle of proper resource management as outlined in the Linux kernel coding guidelines. System administrators should ensure that affected kernel versions are updated to patches that implement the corrected cleanup sequence, typically found in kernel versions 5.19 and later. Organizations maintaining embedded systems or development environments should prioritize kernel updates to address this vulnerability and prevent potential system crashes during normal operational procedures.
This vulnerability demonstrates characteristics consistent with CWE-476 Null Pointer Dereference, where the absence of proper null checks leads to system crashes during cleanup operations. The issue also relates to ATT&CK technique T1489, which covers system shutdown and reboot manipulation, as the vulnerability can cause unexpected system instability during normal shutdown procedures. The fix implemented addresses the temporal dependency issue by ensuring proper ordering of cleanup operations, thereby preventing the conditions that led to the null pointer dereference. This represents a standard defensive programming approach that emphasizes proper resource management and cleanup sequence adherence in kernel drivers, particularly those handling debugfs interfaces and platform device registration.