[NETFILTER]: xt_tables: add centralized error checking

Introduce new functions for common match/target checks (private data
size, valid hooks, valid tables and valid protocols) to get more consistent
error reporting and to avoid each module duplicating them.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 65 insertions, 7 deletions

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index d7817afc6b96..750b92829766 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -52,6 +52,12 @@ enum {
         MATCH,
 };
 
+static const char *xt_prefix[NPROTO] = {
+        [AF_INET]       = "ip",
+        [AF_INET6]      = "ip6",
+        [NF_ARP]        = "arp",
+};
+
 /* Registration hooks for targets. */
 int
 xt_register_target(int af, struct xt_target *target)
@@ -158,18 +164,12 @@ struct xt_target *xt_find_target(int af, const char *name, u8 revision)
 }
 EXPORT_SYMBOL(xt_find_target);
 
-static const char *xt_prefix[NPROTO] = {
-        [AF_INET]       = "ipt_%s",
-        [AF_INET6]      = "ip6t_%s",
-        [NF_ARP]        = "arpt_%s",
-};
-
 struct xt_target *xt_request_find_target(int af, const char *name, u8 revision)
 {
         struct xt_target *target;
 
         target = try_then_request_module(xt_find_target(af, name, revision),
-                                         xt_prefix[af], name);
+                                         "%st_%s", xt_prefix[af], name);
         if (IS_ERR(target) || !target)
                 return NULL;
         return target;
@@ -237,6 +237,64 @@ int xt_find_revision(int af, const char *name, u8 revision, int target,
 }
 EXPORT_SYMBOL_GPL(xt_find_revision);
 
+int xt_check_match(const struct xt_match *match, unsigned short family,
+                   unsigned int size, const char *table, unsigned int hook_mask,
+                   unsigned short proto, int inv_proto)
+{
+        if (XT_ALIGN(match->matchsize) != size) {
+                printk("%s_tables: %s match: invalid size %Zu != %u\n",
+                       xt_prefix[family], match->name,
+                       XT_ALIGN(match->matchsize), size);
+                return -EINVAL;
+        }
+        if (match->table && strcmp(match->table, table)) {
+                printk("%s_tables: %s match: only valid in %s table, not %s\n",
+                       xt_prefix[family], match->name, match->table, table);
+                return -EINVAL;
+        }
+        if (match->hooks && (hook_mask & ~match->hooks) != 0) {
+                printk("%s_tables: %s match: bad hook_mask %u\n",
+                       xt_prefix[family], match->name, hook_mask);
+                return -EINVAL;
+        }
+        if (match->proto && (match->proto != proto || inv_proto)) {
+                printk("%s_tables: %s match: only valid for protocol %u\n",
+                       xt_prefix[family], match->name, match->proto);
+                return -EINVAL;
+        }
+        return 0;
+}
+EXPORT_SYMBOL_GPL(xt_check_match);
+
+int xt_check_target(const struct xt_target *target, unsigned short family,
+                    unsigned int size, const char *table, unsigned int hook_mask,
+                    unsigned short proto, int inv_proto)
+{
+        if (XT_ALIGN(target->targetsize) != size) {
+                printk("%s_tables: %s target: invalid size %Zu != %u\n",
+                       xt_prefix[family], target->name,
+                       XT_ALIGN(target->targetsize), size);
+                return -EINVAL;
+        }
+        if (target->table && strcmp(target->table, table)) {
+                printk("%s_tables: %s target: only valid in %s table, not %s\n",
+                       xt_prefix[family], target->name, target->table, table);
+                return -EINVAL;
+        }
+        if (target->hooks && (hook_mask & ~target->hooks) != 0) {
+                printk("%s_tables: %s target: bad hook_mask %u\n",
+                       xt_prefix[family], target->name, hook_mask);
+                return -EINVAL;
+        }
+        if (target->proto && (target->proto != proto || inv_proto)) {
+                printk("%s_tables: %s target: only valid for protocol %u\n",
+                       xt_prefix[family], target->name, target->proto);
+                return -EINVAL;
+        }
+        return 0;
+}
+EXPORT_SYMBOL_GPL(xt_check_target);
+
 struct xt_table_info *xt_alloc_table_info(unsigned int size)
 {
         struct xt_table_info *newinfo;