netfilter: xtables: add and use xt_request_find_table_lock

currently we always return -ENOENT to userspace if we can't find
a particular table, or if the table initialization fails.

Followup patch will make nat table init fail in case nftables already
registered a nat hook so this change makes xt_find_table_lock return
an ERR_PTR to return the errno value reported from the table init
function.

Add xt_request_find_table_lock as try_then_request_module replacement
and use it where needed.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

2 files changed, 24 insertions, 28 deletions

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 0c3c944a7b72..bf8a5340f15e 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -810,9 +810,8 @@ static int get_info(struct net *net, void __user *user,
 	if (compat)
 		xt_compat_lock(NFPROTO_ARP);
 #endif
-	t = try_then_request_module(xt_find_table_lock(net, NFPROTO_ARP, name),
-				    "arptable_%s", name);
-	if (t) {
+	t = xt_request_find_table_lock(net, NFPROTO_ARP, name);
+	if (!IS_ERR(t)) {
 		struct arpt_getinfo info;
 		const struct xt_table_info *private = t->private;
 #ifdef CONFIG_COMPAT
@@ -841,7 +840,7 @@ static int get_info(struct net *net, void __user *user,
 		xt_table_unlock(t);
 		module_put(t->me);
 	} else
-		ret = -ENOENT;
+		ret = PTR_ERR(t);
 #ifdef CONFIG_COMPAT
 	if (compat)
 		xt_compat_unlock(NFPROTO_ARP);
@@ -866,7 +865,7 @@ static int get_entries(struct net *net, struct arpt_get_entries __user *uptr,
 	get.name[sizeof(get.name) - 1] = '\0';
 
 	t = xt_find_table_lock(net, NFPROTO_ARP, get.name);
-	if (t) {
+	if (!IS_ERR(t)) {
 		const struct xt_table_info *private = t->private;
 
 		if (get.size == private->size)
@@ -878,7 +877,7 @@ static int get_entries(struct net *net, struct arpt_get_entries __user *uptr,
 		module_put(t->me);
 		xt_table_unlock(t);
 	} else
-		ret = -ENOENT;
+		ret = PTR_ERR(t);
 
 	return ret;
 }
@@ -903,10 +902,9 @@ static int __do_replace(struct net *net, const char *name,
 		goto out;
 	}
 
-	t = try_then_request_module(xt_find_table_lock(net, NFPROTO_ARP, name),
-				    "arptable_%s", name);
-	if (!t) {
-		ret = -ENOENT;
+	t = xt_request_find_table_lock(net, NFPROTO_ARP, name);
+	if (IS_ERR(t)) {
+		ret = PTR_ERR(t);
 		goto free_newinfo_counters_untrans;
 	}
 
@@ -1020,8 +1018,8 @@ static int do_add_counters(struct net *net, const void __user *user,
 		return PTR_ERR(paddc);
 
 	t = xt_find_table_lock(net, NFPROTO_ARP, tmp.name);
-	if (!t) {
-		ret = -ENOENT;
+	if (IS_ERR(t)) {
+		ret = PTR_ERR(t);
 		goto free;
 	}
 
@@ -1408,7 +1406,7 @@ static int compat_get_entries(struct net *net,
 
 	xt_compat_lock(NFPROTO_ARP);
 	t = xt_find_table_lock(net, NFPROTO_ARP, get.name);
-	if (t) {
+	if (!IS_ERR(t)) {
 		const struct xt_table_info *private = t->private;
 		struct xt_table_info info;
 
@@ -1423,7 +1421,7 @@ static int compat_get_entries(struct net *net,
 		module_put(t->me);
 		xt_table_unlock(t);
 	} else
-		ret = -ENOENT;
+		ret = PTR_ERR(t);
 
 	xt_compat_unlock(NFPROTO_ARP);
 	return ret;
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 2e0d339028bb..0b975aa2d363 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -973,9 +973,8 @@ static int get_info(struct net *net, void __user *user,
 	if (compat)
 		xt_compat_lock(AF_INET);
 #endif
-	t = try_then_request_module(xt_find_table_lock(net, AF_INET, name),
-				    "iptable_%s", name);
-	if (t) {
+	t = xt_request_find_table_lock(net, AF_INET, name);
+	if (!IS_ERR(t)) {
 		struct ipt_getinfo info;
 		const struct xt_table_info *private = t->private;
 #ifdef CONFIG_COMPAT
@@ -1005,7 +1004,7 @@ static int get_info(struct net *net, void __user *user,
 		xt_table_unlock(t);
 		module_put(t->me);
 	} else
-		ret = -ENOENT;
+		ret = PTR_ERR(t);
 #ifdef CONFIG_COMPAT
 	if (compat)
 		xt_compat_unlock(AF_INET);
@@ -1030,7 +1029,7 @@ get_entries(struct net *net, struct ipt_get_entries __user *uptr,
 	get.name[sizeof(get.name) - 1] = '\0';
 
 	t = xt_find_table_lock(net, AF_INET, get.name);
-	if (t) {
+	if (!IS_ERR(t)) {
 		const struct xt_table_info *private = t->private;
 		if (get.size == private->size)
 			ret = copy_entries_to_user(private->size,
@@ -1041,7 +1040,7 @@ get_entries(struct net *net, struct ipt_get_entries __user *uptr,
 		module_put(t->me);
 		xt_table_unlock(t);
 	} else
-		ret = -ENOENT;
+		ret = PTR_ERR(t);
 
 	return ret;
 }
@@ -1064,10 +1063,9 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks,
 		goto out;
 	}
 
-	t = try_then_request_module(xt_find_table_lock(net, AF_INET, name),
-				    "iptable_%s", name);
-	if (!t) {
-		ret = -ENOENT;
+	t = xt_request_find_table_lock(net, AF_INET, name);
+	if (IS_ERR(t)) {
+		ret = PTR_ERR(t);
 		goto free_newinfo_counters_untrans;
 	}
 
@@ -1181,8 +1179,8 @@ do_add_counters(struct net *net, const void __user *user,
 		return PTR_ERR(paddc);
 
 	t = xt_find_table_lock(net, AF_INET, tmp.name);
-	if (!t) {
-		ret = -ENOENT;
+	if (IS_ERR(t)) {
+		ret = PTR_ERR(t);
 		goto free;
 	}
 
@@ -1625,7 +1623,7 @@ compat_get_entries(struct net *net, struct compat_ipt_get_entries __user *uptr,
 
 	xt_compat_lock(AF_INET);
 	t = xt_find_table_lock(net, AF_INET, get.name);
-	if (t) {
+	if (!IS_ERR(t)) {
 		const struct xt_table_info *private = t->private;
 		struct xt_table_info info;
 		ret = compat_table_info(private, &info);
@@ -1639,7 +1637,7 @@ compat_get_entries(struct net *net, struct compat_ipt_get_entries __user *uptr,
 		module_put(t->me);
 		xt_table_unlock(t);
 	} else
-		ret = -ENOENT;
+		ret = PTR_ERR(t);
 
 	xt_compat_unlock(AF_INET);
 	return ret;