CVE-2026-98669 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
iio: buffer: serialize buffer teardown with mode claims
Buffer-mode claims hold mlock to guarantee that the device remains in buffer mode until the claim is released. Normal buffer updates take info_exist_lock followed by mlock in iio_update_buffers().
However, iio_device_unregister() disables and deactivates all buffers without taking mlock. This can invalidate buffer state, including active_scan_mask, while a buffer-mode claim is held.
Take mlock in iio_disable_all_buffers() so that unregister honors the mode-claim lifetime guarantee. The info_exist_lock -> mlock ordering matches iio_update_buffers().
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Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel's Industrial I/O subsystem contains a synchronization flaw within its buffer management logic, specifically involving the interaction between device unregistration and active buffer-mode claims. This vulnerability arises from an inconsistent locking strategy that fails to maintain mutual exclusion during critical state transitions. The core issue lies in how the system handles the teardown of buffers when a device is being removed or disabled compared to how it manages normal operational updates. In standard operation, functions like iio_update_buffers correctly acquire both info_exist_lock and mlock in a specific order to ensure that buffer states remain consistent while claims are active. However, the function responsible for disabling all buffers during unregistration, iio_disable_all_buffers(), omits the acquisition of mlock entirely. This omission creates a race condition where the kernel can invalidate critical buffer state data structures while external entities still hold valid references or mode claims to those resources.
Buffer-mode claims are designed to guarantee that an Industrial I/O device remains in a specific operational mode until the claim is explicitly released by the consumer. To enforce this guarantee, these claims rely on holding mlock, which acts as a mutex protecting the buffer configuration from concurrent modification. When iio_device_unregister() executes, it proceeds to disable and deactivate all associated buffers without respecting this locking mechanism. Consequently, operations such as clearing or modifying the active_scan_mask can occur simultaneously with code that assumes the device is still in buffer mode due to an outstanding claim. This race condition leads to a state of inconsistency where the kernel's internal representation of the hardware configuration diverges from the expectations of userspace applications or drivers holding claims. The result is potential use-after-free scenarios, data corruption within scan masks, or undefined behavior as the system attempts to access resources that are being torn down without proper synchronization barriers.
The operational impact of this vulnerability extends beyond simple instability; it poses significant risks to system reliability and security integrity in environments relying on Industrial I/O devices for critical monitoring or control tasks. An attacker with local access who can trigger device unregistration while holding buffer-mode claims could exploit this race condition to corrupt kernel memory structures. This corruption may lead to a denial of service through kernel panics or, more severely, facilitate privilege escalation if the corrupted state allows for arbitrary code execution primitives such as writing to unintended memory locations via dangling pointers in the scan mask handling logic. The lack of proper serialization means that timing-based attacks could reliably trigger these inconsistencies, making this a persistent threat in systems where Industrial I/O devices are dynamically managed or frequently reconfigured.
To mitigate this vulnerability, the Linux kernel developers have implemented a fix by ensuring that iio_disable_all_buffers() acquires mlock before proceeding with buffer deactivation. This change aligns the locking sequence during unregistration with the established pattern used in normal buffer updates, specifically maintaining the info_exist_lock followed by mlock ordering. By enforcing this synchronization, the system guarantees that no buffer state modifications can occur while a mode claim is active, thereby preserving the integrity of data structures like active_scan_mask throughout the device lifecycle. System administrators and developers should ensure their kernels are updated to include this patch. Additionally, auditing code paths that interact with Industrial I/O buffers for similar locking inconsistencies is recommended to prevent related issues in custom drivers or extensions. Adhering strictly to established lock ordering conventions within subsystems is essential for maintaining robust concurrency control and preventing race conditions that compromise system stability.