Subject: [PATCH 4/9] netfilter: x_tables: validate e->target_offset early

From: Pablo Neira Ayuso <[email-masked]>
Date: Mon, 28 Mar 2016 19:57:57 +0200

From: Florian Westphal <[email-masked]>

We should check that e->target_offset is sane before
mark_source_chains gets called since it will fetch the target entry
for loop detection.

Signed-off-by: Florian Westphal <[email-masked]>
Signed-off-by: Pablo Neira Ayuso <[email-masked]>
---
 net/ipv4/netfilter/arp_tables.c | 17 ++++++++---------
 net/ipv4/netfilter/ip_tables.c  | 17 ++++++++---------
 net/ipv6/netfilter/ip6_tables.c | 17 ++++++++---------
 3 files changed, 24 insertions(+), 27 deletions(-)

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index bf08192..830bbe8 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -474,14 +474,12 @@ next:
 	return 1;
 }
 
-static inline int check_entry(const struct arpt_entry *e, const char *name)
+static inline int check_entry(const struct arpt_entry *e)
 {
 	const struct xt_entry_target *t;
 
-	if (!arp_checkentry(&e->arp)) {
-		duprintf("arp_tables: arp check failed %p %s.\n", e, name);
+	if (!arp_checkentry(&e->arp))
 		return -EINVAL;
-	}
 
 	if (e->target_offset + sizeof(struct xt_entry_target) > e->next_offset)
 		return -EINVAL;
@@ -522,10 +520,6 @@ find_check_entry(struct arpt_entry *e, const char *name, unsigned int size)
 	struct xt_target *target;
 	int ret;
 
-	ret = check_entry(e, name);
-	if (ret)
-		return ret;
-
 	e->counters.pcnt = xt_percpu_counter_alloc();
 	if (IS_ERR_VALUE(e->counters.pcnt))
 		return -ENOMEM;
@@ -576,6 +570,7 @@ static inline int check_entry_size_and_hooks(struct arpt_entry *e,
 					     unsigned int valid_hooks)
 {
 	unsigned int h;
+	int err;
 
 	if ((unsigned long)e % __alignof__(struct arpt_entry) != 0 ||
 	    (unsigned char *)e + sizeof(struct arpt_entry) >= limit) {
@@ -590,6 +585,10 @@ static inline int check_entry_size_and_hooks(struct arpt_entry *e,
 		return -EINVAL;
 	}
 
+	err = check_entry(e);
+	if (err)
+		return err;
+
 	/* Check hooks & underflows */
 	for (h = 0; h < NF_ARP_NUMHOOKS; h++) {
 		if (!(valid_hooks & (1 << h)))
@@ -1246,7 +1245,7 @@ check_compat_entry_size_and_hooks(struct compat_arpt_entry *e,
 	}
 
 	/* For purposes of check_entry casting the compat entry is fine */
-	ret = check_entry((struct arpt_entry *)e, name);
+	ret = check_entry((struct arpt_entry *)e);
 	if (ret)
 		return ret;
 
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index e53f8d6..1d72a3c 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -569,14 +569,12 @@ static void cleanup_match(struct xt_entry_match *m, struct net *net)
 }
 
 static int
-check_entry(const struct ipt_entry *e, const char *name)
+check_entry(const struct ipt_entry *e)
 {
 	const struct xt_entry_target *t;
 
-	if (!ip_checkentry(&e->ip)) {
-		duprintf("ip check failed %p %s.\n", e, name);
+	if (!ip_checkentry(&e->ip))
 		return -EINVAL;
-	}
 
 	if (e->target_offset + sizeof(struct xt_entry_target) >
 	    e->next_offset)
@@ -666,10 +664,6 @@ find_check_entry(struct ipt_entry *e, struct net *net, const char *name,
 	struct xt_mtchk_param mtpar;
 	struct xt_entry_match *ematch;
 
-	ret = check_entry(e, name);
-	if (ret)
-		return ret;
-
 	e->counters.pcnt = xt_percpu_counter_alloc();
 	if (IS_ERR_VALUE(e->counters.pcnt))
 		return -ENOMEM;
@@ -741,6 +735,7 @@ check_entry_size_and_hooks(struct ipt_entry *e,
 			   unsigned int valid_hooks)
 {
 	unsigned int h;
+	int err;
 
 	if ((unsigned long)e % __alignof__(struct ipt_entry) != 0 ||
 	    (unsigned char *)e + sizeof(struct ipt_entry) >= limit) {
@@ -755,6 +750,10 @@ check_entry_size_and_hooks(struct ipt_entry *e,
 		return -EINVAL;
 	}
 
+	err = check_entry(e);
+	if (err)
+		return err;
+
 	/* Check hooks & underflows */
 	for (h = 0; h < NF_INET_NUMHOOKS; h++) {
 		if (!(valid_hooks & (1 << h)))
@@ -1506,7 +1505,7 @@ check_compat_entry_size_and_hooks(struct compat_ipt_entry *e,
 	}
 
 	/* For purposes of check_entry casting the compat entry is fine */
-	ret = check_entry((struct ipt_entry *)e, name);
+	ret = check_entry((struct ipt_entry *)e);
 	if (ret)
 		return ret;
 
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 84f9baf..26a5ad1 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -581,14 +581,12 @@ static void cleanup_match(struct xt_entry_match *m, struct net *net)
 }
 
 static int
-check_entry(const struct ip6t_entry *e, const char *name)
+check_entry(const struct ip6t_entry *e)
 {
 	const struct xt_entry_target *t;
 
-	if (!ip6_checkentry(&e->ipv6)) {
-		duprintf("ip_tables: ip check failed %p %s.\n", e, name);
+	if (!ip6_checkentry(&e->ipv6))
 		return -EINVAL;
-	}
 
 	if (e->target_offset + sizeof(struct xt_entry_target) >
 	    e->next_offset)
@@ -679,10 +677,6 @@ find_check_entry(struct ip6t_entry *e, struct net *net, const char *name,
 	struct xt_mtchk_param mtpar;
 	struct xt_entry_match *ematch;
 
-	ret = check_entry(e, name);
-	if (ret)
-		return ret;
-
 	e->counters.pcnt = xt_percpu_counter_alloc();
 	if (IS_ERR_VALUE(e->counters.pcnt))
 		return -ENOMEM;
@@ -753,6 +747,7 @@ check_entry_size_and_hooks(struct ip6t_entry *e,
 			   unsigned int valid_hooks)
 {
 	unsigned int h;
+	int err;
 
 	if ((unsigned long)e % __alignof__(struct ip6t_entry) != 0 ||
 	    (unsigned char *)e + sizeof(struct ip6t_entry) >= limit) {
@@ -767,6 +762,10 @@ check_entry_size_and_hooks(struct ip6t_entry *e,
 		return -EINVAL;
 	}
 
+	err = check_entry(e);
+	if (err)
+		return err;
+
 	/* Check hooks & underflows */
 	for (h = 0; h < NF_INET_NUMHOOKS; h++) {
 		if (!(valid_hooks & (1 << h)))
@@ -1518,7 +1517,7 @@ check_compat_entry_size_and_hooks(struct compat_ip6t_entry *e,
 	}
 
 	/* For purposes of check_entry casting the compat entry is fine */
-	ret = check_entry((struct ip6t_entry *)e, name);
+	ret = check_entry((struct ip6t_entry *)e);
 	if (ret)
 		return ret;
 
-- 
2.1.4