Executive brief
In the Linux kernel, the following vulnerability has been resolved:
net: ibm: emac: mal: fix potential system hang in mal_remove()
napi_disable() is not idempotent and calling it on an already-disabled or unenabled NAPI context will cause the kernel to spin indefinitely waiting for the NAPI_STATE_SCHED bit to clear.
In mal_remove(), napi_disable() is called unconditionally. If no MACs were registered, NAPI was never enabled. Also, if they were registered but subsequently unregistered, NAPI was already disabled in mal_unregister_commac(). In either case, calling napi_disable() causes the kernel to hang upon module removal.
Fix this by only calling napi_disable() in mal_remove() if the commac list is not empty (which implies NAPI is enabled).