On Wed, Sep 06, 2023 at 01:47:34PM +0200, Pablo Neira Ayuso wrote: > On Wed, Sep 06, 2023 at 01:32:50PM +0200, Phil Sutter wrote: > > On Wed, Sep 06, 2023 at 11:42:02AM +0200, Pablo Neira Ayuso wrote: > > > Deliver audit log from __nf_tables_dump_rules(), table dereference at > > > the end of the table list loop might point to the list head, leading to > > > this crash. > > > > Ah, of course. Sorry for the mess. I missed the fact that one may just > > call 'reset rules' and have it apply to all existing tables. > > > > [...] > > > Deliver audit log only once at the end of the rule dump+reset for > > > consistency with the set dump+reset. > > > > This may seem like number of audit logs is reduced, when it is actually > > increased: With your patch, there will be at least one notification for > > each chain, multiple with large chains (due to skb exhaustion). > > With your patch, this is called for each netlink_recvmsg() invocation, > which is more audit logs. > > @@ -3540,9 +3544,6 @@ static int nf_tables_dump_rules(struct sk_buff *skb, > done: > rcu_read_unlock(); > > - if (reset && idx > cb->args[0]) > - audit_log_rule_reset(table, cb->seq, idx - cb->args[0]); > - > cb->args[0] = idx; > return skb->len; > } > > netlink dump is composed of a series of recvmsg() from userspace to > fetch the multiple chunks that represent the rules in this table. > If I read fine above, as the netlink dump makes progress, idx will > always go over cb->args[0], which evaluates true for each recvmsg() > call. With my patch this is less audit logs because audit log is only > delivered once for each chain, not for each recvmsg() call. Here's a simple example: | for table in t1 t2; do | echo "add table $table" | for chain in c1 c2 c3; do | echo "add chain $table $chain" | echo "add rule $table $chain counter accept" | echo "add rule $table $chain counter accept" | echo "add rule $table $chain counter accept" | done | done | nft -f - | nft reset rules | nft reset rules table t1 Before your patch, audit NETFILTER_CFG messages are: | type=NETFILTER_CFG msg=audit(1694018800.149:1917): table=(null):5 family=0 entries=18 op=nft_reset_rule pid=6558 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694018848.399:1918): table=t1:5 family=2 entries=9 op=nft_reset_rule pid=6565 subj=kernel comm="nft" (Note the NULL table name pointer in the first one.) With your patch applied, these are the respective audit messages: | type=NETFILTER_CFG msg=audit(1694020131.459:3): table=t1:2 family=2 entries=3 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.459:3): table=t1:2 family=2 entries=6 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.459:3): table=t1:2 family=2 entries=9 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.459:3): table=t2:2 family=2 entries=12 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.459:3): table=t2:2 family=2 entries=15 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.459:3): table=t2:2 family=2 entries=18 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.489:4): table=t1:2 family=2 entries=3 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.489:4): table=t1:2 family=2 entries=6 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.489:4): table=t1:2 family=2 entries=9 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.489:4): table=t2:2 family=2 entries=12 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.489:4): table=t2:2 family=2 entries=15 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020131.489:4): table=t2:2 family=2 entries=18 op=nft_reset_rule pid=3119 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020206.579:5): table=t1:2 family=2 entries=3 op=nft_reset_rule pid=3126 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020206.579:5): table=t1:2 family=2 entries=6 op=nft_reset_rule pid=3126 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020206.579:5): table=t1:2 family=2 entries=9 op=nft_reset_rule pid=3126 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020206.609:6): table=t1:2 family=2 entries=3 op=nft_reset_rule pid=3126 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020206.609:6): table=t1:2 family=2 entries=6 op=nft_reset_rule pid=3126 subj=kernel comm="nft" | type=NETFILTER_CFG msg=audit(1694020206.609:6): table=t1:2 family=2 entries=9 op=nft_reset_rule pid=3126 subj=kernel comm="nft" The last six come from the 'reset rules table t1' command. While on one hand it looks like nftables fits only three rules into a single skb, your fix seems to have a problem in that it doesn't subtract s_idx from *idx. Cheers, Phil
