[SRU Jammy, OEM-6.1, Lunar 2/2] netfilter: nf_tables: disallow rule removal from chain binding

[Thadeu Lima de Souza Cascardo]

From: Pablo Neira Ayuso <pablo at netfilter.org>

Chain binding only requires the rule addition/insertion command within
the same transaction. Removal of rules from chain bindings within the
same transaction makes no sense, userspace does not utilize this
feature. Replace nft_chain_is_bound() check to nft_chain_binding() in
rule deletion commands. Replace command implies a rule deletion, reject
this command too.

Rule flush command can also safely rely on this nft_chain_binding()
check because unbound chains are not allowed since 62e1e94b246e
("netfilter: nf_tables: reject unbound chain set before commit phase").

Fixes: d0e2c7de92c7 ("netfilter: nf_tables: add NFT_CHAIN_BINDING")
Reported-by: Kevin Rich <kevinrich1337 at gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
(backported from commit f15f29fd4779be8a418b66e9d52979bb6d6c2325)
[cascardo: context conflict fixup due to missing 7d937b107108f918906fc867ea070cc3d0cbcd32]
CVE-2023-5197
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
---
 net/netfilter/nf_tables_api.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index aeca514d54df..4f472f73ea75 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1420,7 +1420,7 @@ static int nft_flush_table(struct nft_ctx *ctx)
 		if (!nft_is_active_next(ctx->net, chain))
 			continue;
 
-		if (nft_chain_is_bound(chain))
+		if (nft_chain_binding(chain))
 			continue;
 
 		ctx->chain = chain;
@@ -1465,7 +1465,7 @@ static int nft_flush_table(struct nft_ctx *ctx)
 		if (!nft_is_active_next(ctx->net, chain))
 			continue;
 
-		if (nft_chain_is_bound(chain))
+		if (nft_chain_binding(chain))
 			continue;
 
 		ctx->chain = chain;
@@ -2793,6 +2793,9 @@ static int nf_tables_delchain(struct sk_buff *skb, const struct nfnl_info *info,
 		return PTR_ERR(chain);
 	}
 
+	if (nft_chain_binding(chain))
+		return -EOPNOTSUPP;
+
 	if (info->nlh->nlmsg_flags & NLM_F_NONREC &&
 	    chain->use > 0)
 		return -EBUSY;
@@ -3818,6 +3821,11 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
 	}
 
 	if (info->nlh->nlmsg_flags & NLM_F_REPLACE) {
+		if (nft_chain_binding(chain)) {
+			err = -EOPNOTSUPP;
+			goto err_destroy_flow_rule;
+		}
+
 		err = nft_delrule(&ctx, old_rule);
 		if (err < 0)
 			goto err_destroy_flow_rule;
@@ -3921,7 +3929,7 @@ static int nf_tables_delrule(struct sk_buff *skb, const struct nfnl_info *info,
 			NL_SET_BAD_ATTR(extack, nla[NFTA_RULE_CHAIN]);
 			return PTR_ERR(chain);
 		}
-		if (nft_chain_is_bound(chain))
+		if (nft_chain_binding(chain))
 			return -EOPNOTSUPP;
 	}
 
@@ -3951,7 +3959,7 @@ static int nf_tables_delrule(struct sk_buff *skb, const struct nfnl_info *info,
 		list_for_each_entry(chain, &table->chains, list) {
 			if (!nft_is_active_next(net, chain))
 				continue;
-			if (nft_chain_is_bound(chain))
+			if (nft_chain_binding(chain))
 				continue;
 
 			ctx.chain = chain;
@@ -10470,7 +10478,7 @@ static void __nft_release_table(struct net *net, struct nft_table *table)
 	ctx.family = table->family;
 	ctx.table = table;
 	list_for_each_entry(chain, &table->chains, list) {
-		if (nft_chain_is_bound(chain))
+		if (nft_chain_binding(chain))
 			continue;
 
 		ctx.chain = chain;
-- 
2.34.1