1 files changed, 33 insertions, 18 deletions

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index fdefae6b5dfc..cde755d5eeab 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -8,6 +8,7 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 #include <linux/cache.h>
 #include <linux/capability.h>
 #include <linux/skbuff.h>
@@ -190,16 +191,11 @@ get_entry(void *base, unsigned int offset)
 
 /* All zeroes == unconditional rule. */
 /* Mildly perf critical (only if packet tracing is on) */
-static inline int
-unconditional(const struct ipt_ip *ip)
+static inline bool unconditional(const struct ipt_ip *ip)
 {
-	unsigned int i;
-
-	for (i = 0; i < sizeof(*ip)/sizeof(__u32); i++)
-		if (((__u32 *)ip)[i])
-			return 0;
+	static const struct ipt_ip uncond;
 
-	return 1;
+	return memcmp(ip, &uncond, sizeof(uncond)) == 0;
 #undef FWINV
 }
 
@@ -315,7 +311,6 @@ ipt_do_table(struct sk_buff *skb,
 
 	static const char nulldevname[IFNAMSIZ] __attribute__((aligned(sizeof(long))));
 	const struct iphdr *ip;
-	u_int16_t datalen;
 	bool hotdrop = false;
 	/* Initializing verdict to NF_DROP keeps gcc happy. */
 	unsigned int verdict = NF_DROP;
@@ -328,7 +323,6 @@ ipt_do_table(struct sk_buff *skb,
 
 	/* Initialization */
 	ip = ip_hdr(skb);
-	datalen = skb->len - ip->ihl * 4;
 	indev = in ? in->name : nulldevname;
 	outdev = out ? out->name : nulldevname;
 	/* We handle fragments by dealing with the first fragment as
@@ -427,8 +421,6 @@ ipt_do_table(struct sk_buff *skb,
 #endif
 		/* Target might have changed stuff. */
 		ip = ip_hdr(skb);
-		datalen = skb->len - ip->ihl * 4;
-
 		if (verdict == IPT_CONTINUE)
 			e = ipt_next_entry(e);
 		else
@@ -716,6 +708,21 @@ find_check_entry(struct ipt_entry *e, const char *name, unsigned int size,
 	return ret;
 }
 
+static bool check_underflow(struct ipt_entry *e)
+{
+	const struct ipt_entry_target *t;
+	unsigned int verdict;
+
+	if (!unconditional(&e->ip))
+		return false;
+	t = ipt_get_target(e);
+	if (strcmp(t->u.user.name, XT_STANDARD_TARGET) != 0)
+		return false;
+	verdict = ((struct ipt_standard_target *)t)->verdict;
+	verdict = -verdict - 1;
+	return verdict == NF_DROP || verdict == NF_ACCEPT;
+}
+
 static int
 check_entry_size_and_hooks(struct ipt_entry *e,
 			   struct xt_table_info *newinfo,
@@ -723,6 +730,7 @@ check_entry_size_and_hooks(struct ipt_entry *e,
 			   unsigned char *limit,
 			   const unsigned int *hook_entries,
 			   const unsigned int *underflows,
+			   unsigned int valid_hooks,
 			   unsigned int *i)
 {
 	unsigned int h;
@@ -742,15 +750,21 @@ check_entry_size_and_hooks(struct ipt_entry *e,
 
 	/* Check hooks & underflows */
 	for (h = 0; h < NF_INET_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 IPT_RETURN). --RR */
-
 	/* Clear counters and comefrom */
 	e->counters = ((struct xt_counters) { 0, 0 });
 	e->comefrom = 0;
@@ -813,7 +827,7 @@ translate_table(const char *name,
 				newinfo,
 				entry0,
 				entry0 + size,
-				hook_entries, underflows, &i);
+				hook_entries, underflows, valid_hooks, &i);
 	if (ret != 0)
 		return ret;
 
@@ -2051,7 +2065,8 @@ do_ipt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
 	return ret;
 }
 
-struct xt_table *ipt_register_table(struct net *net, struct xt_table *table,
+struct xt_table *ipt_register_table(struct net *net,
+				    const struct xt_table *table,
 				    const struct ipt_replace *repl)
 {
 	int ret;