Subject: [PATCH net 4/6] netfilter: replace -EEXIST with -EBUSY

From: Florian Westphal <[email-masked]>
Date: Fri, 2 Jan 2026 12:41:26 +0100

From: Daniel Gomez <[email-masked]>

The -EEXIST error code is reserved by the module loading infrastructure
to indicate that a module is already loaded. When a module's init
function returns -EEXIST, userspace tools like kmod interpret this as
"module already loaded" and treat the operation as successful, returning
0 to the user even though the module initialization actually failed.

Replace -EEXIST with -EBUSY to ensure correct error reporting in the module
initialization path.

Affected modules:
  * ebtable_broute ebtable_filter ebtable_nat arptable_filter
  * ip6table_filter ip6table_mangle ip6table_nat ip6table_raw
  * ip6table_security iptable_filter iptable_mangle iptable_nat
  * iptable_raw iptable_security

Signed-off-by: Daniel Gomez <[email-masked]>
Signed-off-by: Florian Westphal <[email-masked]>
---
 net/bridge/netfilter/ebtables.c | 2 +-
 net/netfilter/nf_log.c          | 4 ++--
 net/netfilter/x_tables.c        | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 5697e3949a36..a04fc1757528 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1299,7 +1299,7 @@ int ebt_register_template(const struct ebt_table *t, int (*table_init)(struct ne
 	list_for_each_entry(tmpl, &template_tables, list) {
 		if (WARN_ON_ONCE(strcmp(t->name, tmpl->name) == 0)) {
 			mutex_unlock(&ebt_mutex);
-			return -EEXIST;
+			return -EBUSY;
 		}
 	}
 
diff --git a/net/netfilter/nf_log.c b/net/netfilter/nf_log.c
index 74cef8bf554c..62cf6a30875e 100644
--- a/net/netfilter/nf_log.c
+++ b/net/netfilter/nf_log.c
@@ -89,7 +89,7 @@ int nf_log_register(u_int8_t pf, struct nf_logger *logger)
 	if (pf == NFPROTO_UNSPEC) {
 		for (i = NFPROTO_UNSPEC; i < NFPROTO_NUMPROTO; i++) {
 			if (rcu_access_pointer(loggers[i][logger->type])) {
-				ret = -EEXIST;
+				ret = -EBUSY;
 				goto unlock;
 			}
 		}
@@ -97,7 +97,7 @@ int nf_log_register(u_int8_t pf, struct nf_logger *logger)
 			rcu_assign_pointer(loggers[i][logger->type], logger);
 	} else {
 		if (rcu_access_pointer(loggers[pf][logger->type])) {
-			ret = -EEXIST;
+			ret = -EBUSY;
 			goto unlock;
 		}
 		rcu_assign_pointer(loggers[pf][logger->type], logger);
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 90b7630421c4..48105ea3df15 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1764,7 +1764,7 @@ EXPORT_SYMBOL_GPL(xt_hook_ops_alloc);
 int xt_register_template(const struct xt_table *table,
 			 int (*table_init)(struct net *net))
 {
-	int ret = -EEXIST, af = table->af;
+	int ret = -EBUSY, af = table->af;
 	struct xt_template *t;
 
 	mutex_lock(&xt[af].mutex);
-- 
2.51.2