CVE-2026-98671 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
iio: adc: sun4i-gpadc-iio: clean up on thermal zone registration failure
If devm_thermal_of_zone_register() fails, probe returns without unregistering the IIO map array or disabling runtime PM.
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Analysis
by VulDB Data Team • 10/19/2026
The identified vulnerability resides within the Linux kernel driver for the Allwinner sun4i General Purpose Analog-to-Digital Converter interface, specifically in the initialization sequence managed by the iio_adc_sun4i_gpadc_iio module. This component is responsible for interfacing with hardware thermal sensors and analog input channels on systems utilizing Allwinner SoCs. During the device probe phase, which occurs when the kernel loads the driver and initializes the associated hardware resources, the system attempts to register a thermal zone using the devm_thermal_of_zone_register function. This registration process links the hardware sensor data to the Linux thermal framework, enabling dynamic cooling mechanisms such as throttling or fan control based on temperature readings. The vulnerability arises from an incomplete error handling path when this specific registration step fails due to configuration errors, missing device tree nodes, or other runtime constraints.
When devm_thermal_of_zone_register returns a failure code, the current implementation of the probe function exits immediately without performing necessary cleanup operations for resources that were allocated earlier in the initialization sequence. Specifically, if thermal zone registration fails, the driver does not unregister the Industrial I/O (IIO) map array nor does it disable runtime power management references that may have been acquired during prior steps. This oversight results in a resource leak where memory associated with the IIO maps remains allocated but unreachable, and the device's power management state is left in an inconsistent condition. Over time, repeated failures or frequent driver reloads can lead to cumulative memory exhaustion and potential instability within the kernel subsystem managing these devices.
From a technical perspective, this flaw represents a classic resource leak vulnerability where cleanup logic is not uniformly applied across all exit paths of a function. The lack of proper teardown procedures violates best practices for robust system programming in the Linux kernel environment. According to common weakness enumerations, this issue aligns with CWE-401, which describes missing release of memory after successful allocation, and potentially CWE-755, relating to improper handling of unusual or exceptional input conditions during resource management. The failure to clean up IIO maps means that the system retains references to hardware interfaces that are no longer functional from a thermal monitoring perspective, creating confusion for subsequent operations attempting to access these channels.
The operational impact of this vulnerability is primarily centered around long-term system stability and resource efficiency rather than immediate security exploitation or privilege escalation. While an attacker cannot directly exploit this flaw to gain unauthorized access, the accumulated memory leaks can degrade system performance over extended uptime periods. In embedded systems where resources are constrained, such as those typically found in Allwinner-based devices like single-board computers or IoT appliances, even small per-probe leaks can contribute to eventual out-of-memory conditions. Furthermore, leaving runtime power management enabled for a device that has failed initialization may prevent the system from correctly entering low-power states, leading to increased energy consumption and potential thermal issues unrelated to actual sensor readings.
To mitigate this vulnerability, developers must ensure that all allocated resources are properly released upon any failure path within the probe function. The recommended fix involves restructuring the error handling logic so that control jumps to a dedicated cleanup label when devm_thermal_of_zone_register fails. This cleanup routine should explicitly unregister the IIO map array using appropriate kernel APIs and disable runtime power management for the device if it was previously enabled. By implementing this structured approach to resource deallocation, the driver ensures consistent state regardless of whether initialization succeeds or encounters an error during thermal zone registration.
Adhering to established security standards helps prevent such issues in future development cycles. The ATT&CK framework does not directly categorize kernel-level memory leaks as a specific tactic for initial access, but they fall under broader categories of resource exhaustion that can impact availability. Security audits and static analysis tools should be configured to detect missing cleanup calls in probe functions, particularly those involving complex subsystems like IIO and thermal management. Regular code reviews focusing on error paths are essential to maintain the integrity and reliability of kernel drivers, ensuring that partial initializations do not leave the system in a compromised or degraded state.