In the Linux kernel, the following vulnerability has been resolved:

netfilter: flowtable: publish HW DEAD after worker is done

flow offload work del() sets NF FLOW HW DEAD before the work handler clears NF FLOW HW PENDING. Once a flow is both HW DYING and HW DEAD, a concurrent garbage collection pass can remove it and schedule it for RCU freeing.

The offload worker holds neither an RCU read lock nor a reference to the flow. If it is preempted after publishing HW DEAD, the RCU callback can free the flow before the worker resumes and clears HW PENDING, resulting in a use-after-free.

Move HW DEAD publication to the common worker epilogue after the pending bit is cleared, making it the final flow access by destroy work. Order all preceding flow accesses before publishing the bit that allows garbage collection to free the object.