Currently, if you add a base chain whose name clashes with an existing
non-base chain, nf_tables doesn't complain about this. Similarly, if you
update the chain type, the hook number and priority.
With this patch, nf_tables bails out in case any of this unsupported
operations occur by returning EBUSY.
# nft add table x
# nft add chain x y
# nft add chain x y { type nat hook input priority 0\; }
<cmdline>:1:1-49: Error: Could not process rule: Device or resource busy
add chain x y { type nat hook input priority 0; }
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
net/netfilter/nf_tables_api.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 463fcad..221d27f 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1348,6 +1348,37 @@ static int nf_tables_newchain(struct net *net, struct sock *nlsk,
if (nlh->nlmsg_flags & NLM_F_REPLACE)
return -EOPNOTSUPP;
+ if (nla[NFTA_CHAIN_HOOK]) {
+ struct nft_base_chain *basechain;
+ struct nft_chain_hook hook;
+ struct nf_hook_ops *ops;
+
+ if (!(chain->flags & NFT_BASE_CHAIN))
+ return -EBUSY;
+
+ err = nft_chain_parse_hook(net, nla, afi, &hook,
+ create);
+ if (err < 0)
+ return err;
+
+ basechain = nft_base_chain(chain);
+ if (basechain->type != hook.type) {
+ nft_chain_release_hook(&hook);
+ return -EBUSY;
+ }
+
+ for (i = 0; i < afi->nops; i++) {
+ ops = &basechain->ops[i];
+ if (ops->hooknum != hook.num ||
+ ops->priority != hook.priority ||
+ ops->dev != hook.dev) {
+ nft_chain_release_hook(&hook);
+ return -EBUSY;
+ }
+ }
+ nft_chain_release_hook(&hook);
+ }
+
if (nla[NFTA_CHAIN_HANDLE] && name) {
struct nft_chain *chain2;
--
2.1.4
--
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