CVE-2021-47424

What it actually does

Driver attempts to free an IRQ vector that was never allocated when VSI setup fails during probe, triggering a kernel warning and oops in __free_irq.

Why it matters to the business

Systems using the affected network hardware may experience unexpected crashes during driver initialization, leading to downtime and potential loss of network connectivity until the system is restarted or the driver is fixed.

How an attack unfolds

An attacker with the ability to trigger repeated VSI setup failures (for example via malformed configuration or hardware manipulation) can cause the driver to enter the error path in i40e_probe that calls i40e_clear_interrupt_scheme without the misc IRQ having been requested, resulting in the oops.

How to fix it

Update to a kernel containing the fix that adds a check for the __I40E_MISC_IRQ_REQUESTED state before freeing the misc vector; for the listed opcua-asyncio package apply commit 2be7ce80df05de8d6c6ae1ebce6fa2bb7147844a or later.

How to confirm the fix worked

Confirm the presence of the state check in i40e_clear_interrupt_scheme in the running kernel source or binary; attempt to reproduce the original failure path in a test environment and verify no oops occurs.

Typical attack path

1. Load or reload the i40e driver on a system with the vulnerable code.
2. Induce a failure in VSI or PF switch setup during probe.
3. Allow the error path to invoke i40e_clear_interrupt_scheme.
4. Trigger the unconditional call to i40e_free_misc_vector on an uninitialized vector.

How to detect it

Review kernel logs for the exact warning 'Trying to free already-free IRQ' combined with the call trace containing i40e_clear_interrupt_scheme and i40e_probe; inspect dmesg or syslog around driver load times for the workqueue and IRQ free sequence.

What your security team should do

• Apply the referenced kernel or package update immediately on all affected systems.
• Monitor for kernel oops reports related to i40e IRQ handling during driver load.
• Test driver initialization under failure conditions in staging environments before production rollout.