[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>

2 files changed, 84 insertions, 11 deletions

diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index 6500d4e59d46..b9c37e1e6730 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -92,8 +92,6 @@ struct xt_match
 
         const char name[XT_FUNCTION_MAXNAMELEN-1];
 
-        u_int8_t revision;
-
         /* Return true or false: return FALSE and set *hotdrop = 1 to
            force immediate packet drop. */
         /* Arguments changed since 2.6.9, as this must now handle
@@ -120,6 +118,12 @@ struct xt_match
 
         /* Set this to THIS_MODULE if you are a module, otherwise NULL */
         struct module *me;
+
+        char *table;
+        unsigned int matchsize;
+        unsigned int hooks;
+        unsigned short proto;
+        u_int8_t revision;
 };
 
 /* Registration hooks for targets. */
@@ -129,8 +133,6 @@ struct xt_target
 
         const char name[XT_FUNCTION_MAXNAMELEN-1];
 
-        u_int8_t revision;
-
         /* Returns verdict. Argument order changed since 2.6.9, as this
            must now handle non-linear skbs, using skb_copy_bits and
            skb_ip_make_writable. */
@@ -156,6 +158,12 @@ struct xt_target
 
         /* Set this to THIS_MODULE if you are a module, otherwise NULL */
         struct module *me;
+
+        char *table;
+        unsigned int targetsize;
+        unsigned int hooks;
+        unsigned short proto;
+        u_int8_t revision;
 };
 
 /* Furniture shopping... */
@@ -207,6 +215,13 @@ extern void xt_unregister_target(int af, struct xt_target *target);
 extern int xt_register_match(int af, struct xt_match *target);
 extern void xt_unregister_match(int af, struct xt_match *target);
 
+extern int xt_check_match(const struct xt_match *match, unsigned short family,
+                          unsigned int size, const char *table, unsigned int hook,
+                          unsigned short proto, int inv_proto);
+extern int xt_check_target(const struct xt_target *target, unsigned short family,
+                           unsigned int size, const char *table, unsigned int hook,
+                           unsigned short proto, int inv_proto);
+
 extern int xt_register_table(struct xt_table *table,
                              struct xt_table_info *bootstrap,
                              struct xt_table_info *newinfo);
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;