CVE-2026-99049 in Linux
Summary
by MITRE • 10/23/2026
In the Linux kernel, the following vulnerability has been resolved:
gpio: xilinx: fix runtime PM leak on request error path
pm_runtime_get_sync() leaves the usage counter incremented even when it fails, and xgpio_request() returns the error without dropping it.
gpiolib does not call ->free() when ->request() fails, so xgpio_free(), which holds the only matching pm_runtime_put(), never runs. The reference is leaked and the controller can no longer runtime-suspend, so its clock stays enabled.
Switch to pm_runtime_resume_and_get(), which only increments the usage counter on success.
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Analysis
by VulDB Data Team • 10/23/2026
The identified vulnerability resides within the Linux kernel's GPIO subsystem, specifically affecting the Xilinx GPIO driver implementation. This issue manifests as a resource leak related to runtime power management (PM) during the initialization phase of a GPIO line request. The core technical flaw stems from an improper handling of error conditions in the xgpio_request function. When this function attempts to enable the device for operation using pm_runtime_get_sync, it expects the call to succeed before proceeding with further configuration steps. However, if subsequent operations within the same function fail and trigger a return path indicating an error, the code fails to decrement the usage counter that was incremented by the initial power management call. This oversight creates an imbalance in the reference counting mechanism used by the kernel's runtime PM framework.
The operational impact of this flaw is significant for system stability and power efficiency. Because gpiolib does not invoke the driver-specific free callback when a request fails, the corresponding cleanup function xgpio_free never executes during error paths. Since xgpio_free contains the only call to pm_runtime_put that would normally balance out the earlier get operation, its absence means the usage counter remains artificially elevated. Consequently, the kernel's power management subsystem believes the device is still in active use and prevents it from entering a low-power suspended state. This results in the hardware controller remaining permanently awake with its clock enabled, leading to unnecessary power consumption which can be particularly detrimental in battery-powered or energy-sensitive embedded systems utilizing Xilinx FPGA technology.
From a standards perspective, this vulnerability aligns with CWE-401, which describes a missing release of memory after effective usage, although here the resource is specifically a runtime PM reference count rather than traditional heap memory. The failure to properly manage lifecycle resources on error paths also reflects patterns associated with improper cleanup procedures often seen in system-level software defects. In terms of attack surface and exploitation potential, while this issue does not directly allow for remote code execution or privilege escalation, it contributes to resource exhaustion vectors similar to CWE-400 (Resource Exhaustion). An attacker could potentially exploit repeated allocation failures to keep devices awake indefinitely, contributing to thermal issues or battery drain in constrained environments.
The mitigation strategy implemented involves replacing the pm_runtime_get_sync call with pm_runtime_resume_and_get within the request logic. This newer API function is designed specifically to address this class of bugs by ensuring that the usage counter is only incremented if the resume operation succeeds. If the power management operations fail, the reference count remains unchanged, thereby preserving the balance required for correct runtime PM behavior. Developers and system integrators relying on older kernel versions should apply patches that incorporate this API change or manually implement equivalent error handling logic to decrement the usage counter upon failure. Regular auditing of driver code for proper resource cleanup in all exit paths is recommended to prevent similar leaks across other subsystems within the Linux kernel ecosystem.