Phil Sutter <phil@xxxxxx> wrote: > On Fri, May 05, 2023 at 01:16:53PM +0200, Florian Westphal wrote: > > Keep a per-rule bitmask that tracks registers that have seen a store, > > then reject loads when the accessed registers haven't been flagged. > > > > This changes uabi contract, because we previously allowed this. > > Neither nftables nor iptables-nft create such rules. > > Did you consider keeping this bitmask on a per base-chain level? One had > to perform this for each base chain of a table upon each rule change and > traverse the tree of chains jumped to from there. I guess the huge > overhead disqualifies this, though. Yes, but its very hard task, because in that case we also need to prove that a write *WILL* happen, rather than *might happen*. Consider: rule1: ip protocol tcp iifname "eth0" ... reg1 := ip protocol cmp reg1 reg2 := meta iifname rule2: iifname "eth1" ... cmp reg2 "eth0" rule 2 has to be rejected because reg2 might be unitialized for != tcp. Even if we can handle this some way, we now also need to revalidate the ruleset on deletes, because we'd have to detect when a register write we depend on goes away.
