1 files changed, 31 insertions, 13 deletions

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 7505dff4ffdf..7bc11ffbb845 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -8,7 +8,7 @@
  * Copyright (C) 2002 David S. Miller (davem@redhat.com)
  *
  */
-
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 #include <linux/kernel.h>
 #include <linux/skbuff.h>
 #include <linux/netdevice.h>
@@ -341,15 +341,11 @@ unsigned int arpt_do_table(struct sk_buff *skb,
 }
 
 /* All zeroes == unconditional rule. */
-static inline int unconditional(const struct arpt_arp *arp)
+static inline bool unconditional(const struct arpt_arp *arp)
 {
-	unsigned int i;
+	static const struct arpt_arp uncond;
 
-	for (i = 0; i < sizeof(*arp)/sizeof(__u32); i++)
-		if (((__u32 *)arp)[i])
-			return 0;
-
-	return 1;
+	return memcmp(arp, &uncond, sizeof(uncond)) == 0;
 }
 
 /* Figures out from what hook each rule can be called: returns 0 if
@@ -537,12 +533,28 @@ out:
 	return ret;
 }
 
+static bool check_underflow(struct arpt_entry *e)
+{
+	const struct arpt_entry_target *t;
+	unsigned int verdict;
+
+	if (!unconditional(&e->arp))
+		return false;
+	t = arpt_get_target(e);
+	if (strcmp(t->u.user.name, XT_STANDARD_TARGET) != 0)
+		return false;
+	verdict = ((struct arpt_standard_target *)t)->verdict;
+	verdict = -verdict - 1;
+	return verdict == NF_DROP || verdict == NF_ACCEPT;
+}
+
 static inline int check_entry_size_and_hooks(struct arpt_entry *e,
 					     struct xt_table_info *newinfo,
 					     unsigned char *base,
 					     unsigned char *limit,
 					     const unsigned int *hook_entries,
 					     const unsigned int *underflows,
+					     unsigned int valid_hooks,
 					     unsigned int *i)
 {
 	unsigned int h;
@@ -562,15 +574,21 @@ static inline int check_entry_size_and_hooks(struct arpt_entry *e,
 
 	/* Check hooks & underflows */
 	for (h = 0; h < NF_ARP_NUMHOOKS; h++) {
+		if (!(valid_hooks & (1 << h)))
+			continue;
 		if ((unsigned char *)e - base == hook_entries[h])
 			newinfo->hook_entry[h] = hook_entries[h];
-		if ((unsigned char *)e - base == underflows[h])
+		if ((unsigned char *)e - base == underflows[h]) {
+			if (!check_underflow(e)) {
+				pr_err("Underflows must be unconditional and "
+				       "use the STANDARD target with "
+				       "ACCEPT/DROP\n");
+				return -EINVAL;
+			}
 			newinfo->underflow[h] = underflows[h];
+		}
 	}
 
-	/* FIXME: underflows must be unconditional, standard verdicts
-	   < 0 (not ARPT_RETURN). --RR */
-
 	/* Clear counters and comefrom */
 	e->counters = ((struct xt_counters) { 0, 0 });
 	e->comefrom = 0;
@@ -630,7 +648,7 @@ static int translate_table(const char *name,
 				 newinfo,
 				 entry0,
 				 entry0 + size,
-				 hook_entries, underflows, &i);
+				 hook_entries, underflows, valid_hooks, &i);
 	duprintf("translate_table: ARPT_ENTRY_ITERATE gives %d\n", ret);
 	if (ret != 0)
 		return ret;