commit 90e7d4ab5c8b0c4c2e00e4893977f6aeec0f18f1
Author: Jan Engelhardt <jengelh@xxxxxxxxxx>
Date: Thu Jul 9 22:54:53 2009 +0200
netfilter: xtables: check for unconditionality of policies
This adds a check that iptables's original author Rusty set forth in
a FIXME comment.
Underflows in iptables are better known as chain policies, and are
required to be unconditional or there would be a stochastical chance
for the policy rule to be skipped if it does not match. If that were
to happen, rule execution would continue in an unexpected spurious
fashion.
Signed-off-by: Jan Engelhardt <jengelh@xxxxxxxxxx>
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index d91f083..064082d 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@xxxxxxxxxx)
*
*/
-
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
@@ -563,13 +563,15 @@ static inline int check_entry_size_and_hooks(struct arpt_entry *e,
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 (!unconditional(&e->arp)) {
+ pr_err("Underflows must be unconditional\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;
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 6e7b7e8..6e546d5 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>
@@ -738,13 +739,15 @@ check_entry_size_and_hooks(struct ipt_entry *e,
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 (!unconditional(&e->ip)) {
+ pr_err("Underflows must be unconditional\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;
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 8e4921a..b0599b9 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -8,7 +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/capability.h>
#include <linux/in.h>
#include <linux/skbuff.h>
@@ -771,13 +771,15 @@ check_entry_size_and_hooks(struct ip6t_entry *e,
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 (!unconditional(&e->ipv6)) {
+ pr_err("Underflows must be unconditional\n");
+ return -EINVAL;
+ }
newinfo->underflow[h] = underflows[h];
+ }
}
- /* FIXME: underflows must be unconditional, standard verdicts
- < 0 (not IP6T_RETURN). --RR */
-
/* Clear counters and comefrom */
e->counters = ((struct xt_counters) { 0, 0 });
e->comefrom = 0;
--
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