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@xxxxxxxxx>
---
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 aa5e7b00a581..0969f9647927 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2261,13 +2261,13 @@ 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);
@@ -2287,8 +2287,7 @@ 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))
@@ -2335,7 +2334,7 @@ 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;
@@ -2360,12 +2359,13 @@ 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) {
@@ -2377,11 +2377,13 @@ 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;
@@ -2537,7 +2539,7 @@ 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;
--
2.21.0
