CVE-2023-0179: Linux kernel stack buffer overflow in nftables: PoC and writeup

> ## Patch

> Since the vulnerable operation in nft_payload_copy_vlan should account for the encapsulated VLAN tag, I suspect that the last plus sign should have been a minus since it prevents any wrapping.

> ## Mitigating the bug

> If you are unable to patch this bug, disabling unprivileged user namespaces will prevent exploitation:

    sysctl -w kernel.unprivileged_userns_clone = 0