netfilter: nf_tables: split chain policy validation from actually setting it

Currently nf_tables_newchain() atomicity is broken because of having
validation of some netlink attributes performed after changing attributes
of the chain. The chain policy is (currently) fine, but split it up as
preparation for the following fixes and to avoid future mistakes.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 572d88dd3e5fe027bf9beb4cc61438d9e10d737e..30fad4f6322f33f868d1668029599a0224607292 100644 (file)
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -760,22 +760,6 @@ static int nf_tables_getchain(struct sock *nlsk, struct sk_buff *skb,
        return err;
 }
 
-static int
-nf_tables_chain_policy(struct nft_base_chain *chain, const struct nlattr *attr)
-{
-       switch (ntohl(nla_get_be32(attr))) {
-       case NF_DROP:
-               chain->policy = NF_DROP;
-               break;
-       case NF_ACCEPT:
-               chain->policy = NF_ACCEPT;
-               break;
-       default:
-               return -EINVAL;
-       }
-       return 0;
-}
-
 static const struct nla_policy nft_counter_policy[NFTA_COUNTER_MAX + 1] = {
        [NFTA_COUNTER_PACKETS]  = { .type = NLA_U64 },
        [NFTA_COUNTER_BYTES]    = { .type = NLA_U64 },
@@ -834,6 +818,7 @@ static int nf_tables_newchain(struct sock *nlsk, struct sk_buff *skb,
        struct nlattr *ha[NFTA_HOOK_MAX + 1];
        struct net *net = sock_net(skb->sk);
        int family = nfmsg->nfgen_family;
+       u8 policy = NF_ACCEPT;
        u64 handle = 0;
        unsigned int i;
        int err;
@@ -869,6 +854,22 @@ static int nf_tables_newchain(struct sock *nlsk, struct sk_buff *skb,
                }
        }
 
+       if (nla[NFTA_CHAIN_POLICY]) {
+               if ((chain != NULL &&
+                   !(chain->flags & NFT_BASE_CHAIN)) ||
+                   nla[NFTA_CHAIN_HOOK] == NULL)
+                       return -EOPNOTSUPP;
+
+               policy = nla_get_be32(nla[NFTA_CHAIN_POLICY]);
+               switch (policy) {
+               case NF_DROP:
+               case NF_ACCEPT:
+                       break;
+               default:
+                       return -EINVAL;
+               }
+       }
+
        if (chain != NULL) {
                if (nlh->nlmsg_flags & NLM_F_EXCL)
                        return -EEXIST;
@@ -879,15 +880,8 @@ static int nf_tables_newchain(struct sock *nlsk, struct sk_buff *skb,
                    !IS_ERR(nf_tables_chain_lookup(table, nla[NFTA_CHAIN_NAME])))
                        return -EEXIST;
 
-               if (nla[NFTA_CHAIN_POLICY]) {
-                       if (!(chain->flags & NFT_BASE_CHAIN))
-                               return -EOPNOTSUPP;
-
-                       err = nf_tables_chain_policy(nft_base_chain(chain),
-                                                    nla[NFTA_CHAIN_POLICY]);
-                       if (err < 0)
-                               return err;
-               }
+               if (nla[NFTA_CHAIN_POLICY])
+                       nft_base_chain(chain)->policy = policy;
 
                if (nla[NFTA_CHAIN_COUNTERS]) {
                        if (!(chain->flags & NFT_BASE_CHAIN))
@@ -958,17 +952,7 @@ static int nf_tables_newchain(struct sock *nlsk, struct sk_buff *skb,
                }
 
                chain->flags |= NFT_BASE_CHAIN;
-
-               if (nla[NFTA_CHAIN_POLICY]) {
-                       err = nf_tables_chain_policy(basechain,
-                                                    nla[NFTA_CHAIN_POLICY]);
-                       if (err < 0) {
-                               free_percpu(basechain->stats);
-                               kfree(basechain);
-                               return err;
-                       }
-               } else
-                       basechain->policy = NF_ACCEPT;
+               basechain->policy = policy;
 
                if (nla[NFTA_CHAIN_COUNTERS]) {
                        err = nf_tables_counters(basechain,