CVE-2026-89939 in Linux
Summary
by MITRE • 09/16/2026
In the Linux kernel, the following vulnerability has been resolved:
iio: chemical: atlas-sensor: fix PM reference leak in buffer postenable
atlas_buffer_postenable() acquires a runtime PM reference with pm_runtime_resume_and_get() but returns the result of atlas_set_interrupt() directly. If atlas_set_interrupt() fails, the runtime PM reference is leaked and the device can never autosuspend.
Add pm_runtime_put_autosuspend() on the error path to balance the reference.
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Analysis
by VulDB Data Team • 09/16/2026
The identified vulnerability resides within the Linux kernel's Industrial I/O subsystem, specifically affecting the Atlas chemical sensor driver. This issue manifests as a power management reference leak during the buffer post-enable operation. The core of the problem lies in the implementation of the atlas_buffer_postenable function, which is responsible for preparing the hardware device to begin collecting data via its buffer interface. To ensure the device remains active and responsive while this process occurs, the driver invokes pm_runtime_resume_and_get(). This kernel API serves a dual purpose: it resumes the device from a suspended state if necessary and increments the runtime power management reference count to prevent the system from autosuspending the hardware prematurely during critical operations.
The technical flaw arises because the function immediately returns the result of atlas_set_interrupt() without checking for errors or performing cleanup on failure paths. The atlas_set_interrupt() routine handles the configuration of interrupt lines associated with the sensor data acquisition. If this subroutine encounters an error and returns a negative value, indicating failure to configure interrupts correctly, the atlas_buffer_postenable function propagates that error code back to the caller. However, because it does not execute any cleanup logic before returning, the runtime PM reference acquired earlier by pm_runtime_resume_and_get() remains unreleased. This creates a resource leak where the device's power management reference count is incremented but never decremented in this specific failure scenario.
The operational impact of this vulnerability extends beyond simple memory or counter inefficiency; it directly affects system stability and hardware lifecycle. Since the runtime PM reference count is not balanced, the kernel perceives that there are still active users requiring the device to remain powered on. Consequently, the autosuspend mechanism is effectively disabled for this specific sensor instance. The device will never enter its low-power sleep state, leading to unnecessary power consumption. In battery-operated systems or embedded devices where energy efficiency is critical, this can result in significantly reduced battery life and increased thermal output due to continuous operation of hardware that should be idle when not actively processing data.
From a classification perspective, this vulnerability aligns with CWE-401, which describes the missing release of memory after successful allocation, although here it applies specifically to power management reference counts rather than heap memory. It also relates to improper resource handling during error conditions, often categorized under general logic errors in driver development. In terms of attack surface and exploitation potential, this is primarily a reliability issue rather than a direct security exploit vector like buffer overflow or privilege escalation. However, persistent resource leaks can contribute to denial-of-service scenarios over time by exhausting system resources or causing thermal throttling that degrades overall system performance.
To mitigate this vulnerability, the driver code must be updated to ensure proper reference counting on all execution paths. Specifically, when atlas_set_interrupt() fails and returns an error, the function should invoke pm_runtime_put_autosuspend(). This call decrements the runtime PM reference count acquired earlier and schedules the device for autosuspension after a specified delay if no other users are active. By balancing the acquire operation with a corresponding release on the error path, the driver ensures that the power management state remains consistent regardless of whether interrupt configuration succeeds or fails. This fix restores the expected behavior where the hardware can correctly transition between active and suspended states based on actual usage patterns, thereby preserving energy efficiency and system stability.