CVE-2023-3390: Use-after-free in Linux kernel's netfilter subsystem

A flaw in the Linux Kernel found in the Netfilter nf_tables (net/netfilter/nf_tables_api.c). It can lead to use after free vulnerability in nftables when handling sets that are both named and anonymous in batch requests. Nftables allows creating a named set that can be also marked as anonymous by setting the NFT_SET_ANONYMOUS flag. When a rule referencing this malformed set is destroyed, the set gets destroyed as well, as the set is marked anonymous. It is possible to get nftables to destroy the rule, by mangling certain bytes within the rule's bytecode. As this is a named set, the set can be referenced in a different rule at which point it triggers a use after free. The caveat is that all of this needs to be performed in a batch transaction. This is because the reference of any set created in a batch transaction remains in the transactions list even after the set is destroyed. Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1240eb93f0616b21c675416516ff3d74798fdc97