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netfilter: nf_tables: can't fail after linking rule into active rule list

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rules in nftables a free'd using kfree, but protected by rcu, i.e. we
must wait for a grace period to elapse.

Normal removal patch does this, but nf_tables_newrule() doesn't obey
this rule during error handling.

It calls nft_trans_rule_add() *after* linking rule, and, if that
fails to allocate memory, it unlinks the rule and then kfree() it --
this is unsafe.

Switch order -- first add rule to transaction list, THEN link it
to public list.

Note: nft_trans_rule_add() uses GFP_KERNEL; it will not fail so this
is not a problem in practice (spotted only during code review).

Fixes: 0628b123c9 ("netfilter: nfnetlink: add batch support and use it from nf_tables")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2018-04-10 09:30:27 +02:00 committed by Pablo Neira Ayuso
parent a661574370
commit 569ccae68b
1 changed files with 32 additions and 27 deletions
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29
net/netfilter/nf_tables_api.c
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@ -2361,7 +2361,10 @@ static int nf_tables_newrule(struct net *net, struct sock *nlsk,
}
if (nlh->nlmsg_flags & NLM_F_REPLACE) {
if (nft_is_active_next(net, old_rule)) {
if (!nft_is_active_next(net, old_rule)) {
err = -ENOENT;
goto err2;
}
trans = nft_trans_rule_add(&ctx, NFT_MSG_DELRULE,
old_rule);
if (trans == NULL) {
@ -2370,32 +2373,34 @@ static int nf_tables_newrule(struct net *net, struct sock *nlsk,
}
nft_deactivate_next(net, old_rule);
chain->use--;
list_add_tail_rcu(&rule->list, &old_rule->list);
} else {
err = -ENOENT;
if (nft_trans_rule_add(&ctx, NFT_MSG_NEWRULE, rule) == NULL) {
err = -ENOMEM;
goto err2;
}
} else if (nlh->nlmsg_flags & NLM_F_APPEND)
list_add_tail_rcu(&rule->list, &old_rule->list);
} else {
if (nft_trans_rule_add(&ctx, NFT_MSG_NEWRULE, rule) == NULL) {
err = -ENOMEM;
goto err2;
}
if (nlh->nlmsg_flags & NLM_F_APPEND) {
if (old_rule)
list_add_rcu(&rule->list, &old_rule->list);
else
list_add_tail_rcu(&rule->list, &chain->rules);
else {
} else {
if (old_rule)
list_add_tail_rcu(&rule->list, &old_rule->list);
else
list_add_rcu(&rule->list, &chain->rules);
}
if (nft_trans_rule_add(&ctx, NFT_MSG_NEWRULE, rule) == NULL) {
err = -ENOMEM;
goto err3;
}
chain->use++;
return 0;
err3:
list_del_rcu(&rule->list);
err2:
nf_tables_rule_destroy(&ctx, rule);
err1: