From: Florian Westphal fw@strlen.de
[ Upstream commit 2c82c7e724ff51cab78e1afd5c2aaa31994fe41e ]
We can oops in nf_tables_fill_rule_info().
Its not possible to fetch previous element in rcu-protected lists when deletions are not prevented somehow: list_del_rcu poisons the ->prev pointer value.
Before rcu-conversion this was safe as dump operations did hold nfnetlink mutex.
Pass previous rule as argument, obtained by keeping a pointer to the previous rule during traversal.
Fixes: d9adf22a291883 ("netfilter: nf_tables: use call_rcu in netlink dumps") Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/netfilter/nf_tables_api.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 1606eaa5ae0d..041a81185c6a 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -2256,13 +2256,13 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, struct net *net, u32 flags, int family, const struct nft_table *table, const struct nft_chain *chain, - const struct nft_rule *rule) + const struct nft_rule *rule, + const struct nft_rule *prule) { struct nlmsghdr *nlh; struct nfgenmsg *nfmsg; const struct nft_expr *expr, *next; struct nlattr *list; - const struct nft_rule *prule; u16 type = nfnl_msg_type(NFNL_SUBSYS_NFTABLES, event);
nlh = nlmsg_put(skb, portid, seq, type, sizeof(struct nfgenmsg), flags); @@ -2282,8 +2282,7 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, struct net *net, NFTA_RULE_PAD)) goto nla_put_failure;
- if ((event != NFT_MSG_DELRULE) && (rule->list.prev != &chain->rules)) { - prule = list_prev_entry(rule, list); + if (event != NFT_MSG_DELRULE && prule) { if (nla_put_be64(skb, NFTA_RULE_POSITION, cpu_to_be64(prule->handle), NFTA_RULE_PAD)) @@ -2330,7 +2329,7 @@ static void nf_tables_rule_notify(const struct nft_ctx *ctx,
err = nf_tables_fill_rule_info(skb, ctx->net, ctx->portid, ctx->seq, event, 0, ctx->family, ctx->table, - ctx->chain, rule); + ctx->chain, rule, NULL); if (err < 0) { kfree_skb(skb); goto err; @@ -2355,12 +2354,13 @@ static int __nf_tables_dump_rules(struct sk_buff *skb, const struct nft_chain *chain) { struct net *net = sock_net(skb->sk); + const struct nft_rule *rule, *prule; unsigned int s_idx = cb->args[0]; - const struct nft_rule *rule;
+ prule = NULL; list_for_each_entry_rcu(rule, &chain->rules, list) { if (!nft_is_active(net, rule)) - goto cont; + goto cont_skip; if (*idx < s_idx) goto cont; if (*idx > s_idx) { @@ -2372,11 +2372,13 @@ static int __nf_tables_dump_rules(struct sk_buff *skb, NFT_MSG_NEWRULE, NLM_F_MULTI | NLM_F_APPEND, table->family, - table, chain, rule) < 0) + table, chain, rule, prule) < 0) return 1;
nl_dump_check_consistent(cb, nlmsg_hdr(skb)); cont: + prule = rule; +cont_skip: (*idx)++; } return 0; @@ -2532,7 +2534,7 @@ static int nf_tables_getrule(struct net *net, struct sock *nlsk,
err = nf_tables_fill_rule_info(skb2, net, NETLINK_CB(skb).portid, nlh->nlmsg_seq, NFT_MSG_NEWRULE, 0, - family, table, chain, rule); + family, table, chain, rule, NULL); if (err < 0) goto err;