From 90e7d4ab5c8b0c4c2e00e4893977f6aeec0f18f1 Mon Sep 17 00:00:00 2001 From: Jan Engelhardt Date: Thu, 9 Jul 2009 22:54:53 +0200 Subject: [PATCH] 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 --- net/ipv4/netfilter/arp_tables.c | 12 +++++++----- net/ipv4/netfilter/ip_tables.c | 11 +++++++---- net/ipv6/netfilter/ip6_tables.c | 12 +++++++----- 3 files changed, 21 insertions(+), 14 deletions(-) diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index d91f0834d572..064082dffafb 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 #include #include @@ -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 6e7b7e8b80b1..6e546d573d9c 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 #include #include @@ -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 8e4921a937ff..b0599b98d1b6 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 #include #include @@ -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;