CVE-2026-80678 in Linux
Summary
by MITRE • 08/28/2026
In the Linux kernel, the following vulnerability has been resolved:
i2c: imx: Fix slave registration race and error handling
In i2c_imx_reg_slave(), the slave pointer was assigned before pm_runtime_resume_and_get(). If pm_runtime_resume_and_get() failed, the error path returned without clearing i2c_imx->slave, leaving it non-NULL and causing all subsequent registration attempts to fail with -EBUSY.
Additionally, because this driver uses a shared IRQ, the interrupt handler i2c_imx_isr() can execute concurrently and, after acquiring slave_lock, dereference i2c_imx->slave. The previous fix attempt added a lockless i2c_imx->slave = NULL on the error path, but that could race with the ISR under the lock and still cause a NULL pointer dereference.
Fix both issues by deferring the assignment of i2c_imx->slave and i2c_imx->last_slave_event to after a successful resume, and by performing the assignment inside the slave_lock critical section. This guarantees that the slave pointer is never left stale on the error path and is always valid when observed by the interrupt handler.
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Analysis
by VulDB Data Team • 08/28/2026
The Linux kernel driver for i.MX I2C controllers contained two distinct concurrency-related defects within its slave mode registration logic, specifically in the function i2c_imx_reg_slave(). The first issue was a race condition involving power management and state initialization. During the execution of this function, the driver assigned the pointer to the registered I2C slave device to the internal structure member i2c_imx->slave before attempting to resume the device from a low-power state via pm_runtime_resume_and_get(). If the runtime resume operation failed due to hardware issues or power domain unavailability, the error handling path would return an error code without clearing the previously assigned slave pointer. This left the driver in an inconsistent state where i2c_imx->slave remained non-NULL despite the registration failing. Consequently, any subsequent attempt by userspace or other kernel subsystems to register a new I2C slave device would encounter this stale reference and fail with an -EBUSY error code, effectively locking out legitimate operations until the driver was unloaded and reloaded.
The second issue involved a more severe concurrency vulnerability related to interrupt handling. The i.MX I2C hardware utilizes shared interrupts, meaning that the interrupt service routine i2c_imx_isr() can execute concurrently with registration or unregistration functions. Within this interrupt handler, after acquiring slave_lock, the code dereferences the i2c_imx->slave pointer to process events. A previous attempt to mitigate a similar race condition involved setting the slave pointer to NULL on the error path without holding locks. However, because the assignment was lockless while the interrupt handler accessed it under a spinlock, a classic time-of-check-to-time-of-use scenario emerged. The interrupt could read the pointer after it had been set to NULL by the failed registration cleanup but before other synchronization mechanisms were fully established, leading to a NULL pointer dereference and subsequent kernel panic or system instability. This highlights a critical flaw in handling shared resources where asynchronous hardware events interact with synchronous driver state changes without proper atomicity guarantees.
These vulnerabilities are categorized under CWE-362 for concurrent execution using shared resources with insufficient synchronization, specifically manifesting as race conditions that lead to resource leaks and null pointer dereferences. In the context of the MITRE ATT&CK framework, these flaws relate to techniques involving exploitation of software logic errors rather than memory corruption exploits like buffer overflows, though they result in denial of service through system crashes or functional degradation. The lack of proper locking during state transitions allows external triggers such as power management events and hardware interrupts to expose internal driver inconsistencies that should be encapsulated by the kernel's synchronization primitives.
The resolution addresses both issues by restructuring the order of operations within i2c_imx_reg_slave(). The assignment of i2c_imx->slave is deferred until after pm_runtime_resume_and_get() has successfully completed, ensuring that a valid device context exists before exposing it to other parts of the driver. Furthermore, this assignment and the update of i2c_imx->last_slave_event are performed inside the slave_lock critical section. By holding the lock during these state changes, the driver ensures mutual exclusion with the interrupt handler. This guarantees that when the ISR acquires slave_lock and dereferences the pointer, it is either accessing a fully initialized valid object or sees no assignment at all if registration has not yet begun, thereby eliminating both the stale reference causing -EBUSY errors and the race condition leading to NULL pointer dereferences.
To mitigate similar issues in other drivers, developers should ensure that resource acquisition and state updates are atomic with respect to interrupt handlers. Any shared data structure accessed by an ISR must be protected by appropriate locking mechanisms during all read and write operations, including error paths. Additionally, power management calls like pm_runtime_resume_and_get() should generally precede the exposure of internal pointers to prevent leaving drivers in partially initialized states upon failure. Regular code audits focusing on lock ordering and race conditions between process context and interrupt context are essential for maintaining kernel stability, particularly in hardware abstraction layers where asynchronous events are frequent.