CVE-2026-80559 in Linux
Summary
by MITRE • 08/26/2026
In the Linux kernel, the following vulnerability has been resolved:
Input: sur40 - fix input device registration ordering
In sur40_probe(), input_register_device() was previously called early before the V4L2 video device and vb2_queue components were fully initialized. If userspace opened the input device immediately upon registration, sur40_open() would trigger and start the sur40_poll() worker thread. This worker thread invokes sur40_process_video() and accesses the uninitialized vb2_queue structure, leading to a data race and potential system crash.
Furthermore, if V4L2 or video registration failed after input_register_device() succeeded, the error path fell through to calling input_free_device() on a successfully registered device instead of input_unregister_device(), corrupting input core state.
Move input_register_device() to the very end of sur40_probe(). This ensures the V4L2 and video queue structures are fully initialized before polling can start, and naturally resolves the error path bug since input_free_device() is now only called when input registration has not yet occurred.
To maintain strict LIFO (Last-In, First-Out) teardown ordering, also move input_unregister_device() to the very beginning of sur40_disconnect(). This guarantees that the input polling worker thread is stopped before V4L2 video components or control handlers are unregistered.
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Analysis
by VulDB Data Team • 08/26/2026
The vulnerability in the Linux kernel's sur40 driver stems from an incorrect ordering of device initialization and cleanup operations within the probe and disconnect functions, leading to both race conditions and state corruption issues. The core technical flaw lies in the fact that input_register_device was invoked before the V4L2 video device and vb2_queue components were fully initialized. This premature registration allows userspace applications to open the input device immediately after it is registered by the kernel. When such an opening occurs, the sur40_open function triggers the start of the sur40_poll worker thread. This polling mechanism subsequently invokes sur40_process_video, which attempts to access the vb2_queue structure that has not yet been properly initialized due to the earlier execution order error.
This sequence of events creates a critical data race condition where kernel code accesses uninitialized memory structures. The consequence of this race is unpredictable behavior ranging from corrupted video processing logic to complete system crashes or kernel panics, as the driver attempts to operate on invalid pointers or empty queues. This represents a significant stability risk for systems relying on the sur40 fingerprint sensor hardware, particularly in environments where automated scripts or services might rapidly open and close device nodes upon detection of new hardware.
Beyond the race condition during normal operation, there is also a severe error handling defect within the probe function's failure path. If the registration of the V4L2 video device or other dependent components fails after input_register_device has already succeeded, the existing code incorrectly calls input_free_device instead of input_unregister_device. This misuse corrupts the internal state of the Linux input core subsystem because free operations are intended for devices that were never registered with the system, whereas unregister operations are required to properly detach and clean up active registrations. Such corruption can lead to memory leaks or further instability in subsequent device interactions.
The resolution involves reordering these critical initialization steps by moving input_register_device to the very end of the sur40_probe function. This ensures that all dependent structures, including V4L2 video devices and vb2 queues, are fully initialized before any userspace interaction becomes possible through the registered input node. Additionally, this change naturally resolves the error path bug because if initialization fails later in the probe sequence, the input device has not yet been registered with the core, meaning it is safe to simply free its resources without invoking unregister routines that expect an active registration state.
To maintain strict Last-In First-Out teardown ordering during driver removal or hardware disconnection, input_unregister_device was moved to the very beginning of the sur40_disconnect function. This ensures that the input polling worker thread is stopped and cleaned up before any V4L2 video components or control handlers are unregistered. Proper LIFO ordering in kernel subsystems is essential to prevent use-after-free scenarios where a lower-level component might still be accessed by an upper-layer handler during shutdown, thereby preserving system integrity during device removal events.
From a classification perspective, this vulnerability aligns with CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization due to the data race on uninitialized structures and CWE-459 Incomplete Cleanup which relates to the improper error handling path that corrupts input core state. The exploitation vector falls under ATT&CK technique T1059 Command Scripting if an attacker leverages rapid device opening for denial of service, or potentially T1078 Valid Accounts if local access is required to trigger the race condition effectively against privileged kernel memory spaces.
Mitigation strategies primarily involve applying the upstream Linux kernel patch that corrects this initialization and teardown ordering. For systems unable to update immediately, restricting userspace access to sur40 input devices until system updates are applied can reduce exposure. Administrators should monitor for unexpected kernel panics or log entries related to V4L2 or input subsystem errors following hardware insertion events as indicators of potential exploitation attempts targeting this race condition.