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The vulnerability CVE-2025-37968 is a race condition-induced deadlock within the `opt3001` ambient light sensor driver in the Linux kernel. The flaw resides in the threaded Interrupt Request (IRQ) handler function opt3001_irq(). This function incorrectly reads a shared driver flag (flags) at two separate points: first to decide whether to lock a mutex and again later to decide whether to unlock it.
In a normal, sequential execution, this pattern works. However, in a multi-core or preemptible kernel environment, the state of the flag can be changed by another concurrent execution path (like a sensor data read) between these two reads. A problematic sequence occurs if the first read evaluates as `true` (requiring a mutex lock), but the concurrent code path clears the flag before the second read. This causes the second read to evaluate as false, skipping the `mutex_unlock()` call. The mutex remains permanently locked.
Any subsequent kernel thread that attempts to acquire the same mutex will block indefinitely, waiting for a lock that will never be released. This creates a deadlock, freezing the part of the kernel responsible for the sensor and potentially causing a broader system hang depending on what operations are blocked. The fix involves reading the volatile flag into a local, stable variable at the beginning of the critical section and using this local copy for both the lock and unlock decisions, eliminating the race condition.
Platform: Linux Kernel
Version: With opt3001 driver
Vulnerability: Deadlock race condition
Severity: Not specified
date: 2025-05-20
Prediction: 2025-12-16
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lsmod | grep opt3001 dmesg | grep -i "deadlock|opt3001" cat /sys/bus/iio/devices/iio:device/name
// Vulnerable pattern (simplified)
if (test_flag(flag)) {
mutex_lock(&mutex);
// ... critical section ...
if (test_flag(flag)) { // Second read - RACE CONDITION HERE
mutex_unlock(&mutex);
}
}
// Fixed pattern
bool flag_state = test_flag(flag); // Single, stable read
if (flag_state) {
mutex_lock(&mutex);
}
// ... critical section ...
if (flag_state) { // Uses local variable
mutex_unlock(&mutex);
}
How Exploit
An attacker with local user access can trigger the deadlock by intentionally creating a race condition. This involves simultaneously and repeatedly reading from the `/sys/bus/iio/devices/iio:device/in_illuminance_raw` sysfs interface (or similar) while the sensor is generating interrupts, increasing the probability that the flag changes state between the IRQ handler’s two reads.
Protection from this CVE
Apply the official kernel patch that stores the flag state in a local variable. Update the Linux kernel to a version that includes the fix for this commit. As a workaround, avoid using or unload the `opt3001` kernel module if not required.
Impact
The primary impact is a local Denial-of-Service (DoS). The deadlock causes a kernel thread to hang permanently, which can freeze access to the sensor and, if the locked resource is shared or critical, may lead to a partial or complete system hang requiring a reboot.
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Reported By: nvd.nist.gov
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