85 lines
2.7 KiB
Diff
85 lines
2.7 KiB
Diff
From 57ebd808a97d7c5b1e1afb937c2db22beba3c1f8 Mon Sep 17 00:00:00 2001
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From: Florian Westphal <fw@strlen.de>
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Date: Wed, 7 Feb 2018 13:46:25 +0100
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Subject: [PATCH] netfilter: add back stackpointer size checks
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The rationale for removing the check is only correct for rulesets
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generated by ip(6)tables.
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In iptables, a jump can only occur to a user-defined chain, i.e.
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because we size the stack based on number of user-defined chains we
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cannot exceed stack size.
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However, the underlying binary format has no such restriction,
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and the validation step only ensures that the jump target is a
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valid rule start point.
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IOW, its possible to build a rule blob that has no user-defined
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chains but does contain a jump.
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If this happens, no jump stack gets allocated and crash occurs
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because no jumpstack was allocated.
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Fixes: 7814b6ec6d0d6 ("netfilter: xtables: don't save/restore jumpstack offset")
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Reported-by: syzbot+e783f671527912cd9403@syzkaller.appspotmail.com
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Signed-off-by: Florian Westphal <fw@strlen.de>
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Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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---
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net/ipv4/netfilter/arp_tables.c | 4 ++++
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net/ipv4/netfilter/ip_tables.c | 7 ++++++-
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net/ipv6/netfilter/ip6_tables.c | 4 ++++
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3 files changed, 14 insertions(+), 1 deletion(-)
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diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
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index 4ffe302f9b82..e3e420f3ba7b 100644
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--- a/net/ipv4/netfilter/arp_tables.c
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+++ b/net/ipv4/netfilter/arp_tables.c
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@@ -252,6 +252,10 @@ unsigned int arpt_do_table(struct sk_buff *skb,
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}
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if (table_base + v
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!= arpt_next_entry(e)) {
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+ if (unlikely(stackidx >= private->stacksize)) {
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+ verdict = NF_DROP;
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+ break;
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+ }
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jumpstack[stackidx++] = e;
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}
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diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
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index 9a71f3149507..e38395a8dcf2 100644
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--- a/net/ipv4/netfilter/ip_tables.c
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+++ b/net/ipv4/netfilter/ip_tables.c
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@@ -330,8 +330,13 @@ ipt_do_table(struct sk_buff *skb,
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continue;
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}
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if (table_base + v != ipt_next_entry(e) &&
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- !(e->ip.flags & IPT_F_GOTO))
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+ !(e->ip.flags & IPT_F_GOTO)) {
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+ if (unlikely(stackidx >= private->stacksize)) {
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+ verdict = NF_DROP;
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+ break;
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+ }
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jumpstack[stackidx++] = e;
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+ }
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e = get_entry(table_base, v);
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continue;
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diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
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index af4c917e0836..62358b93bbac 100644
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--- a/net/ipv6/netfilter/ip6_tables.c
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+++ b/net/ipv6/netfilter/ip6_tables.c
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@@ -352,6 +352,10 @@ ip6t_do_table(struct sk_buff *skb,
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}
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if (table_base + v != ip6t_next_entry(e) &&
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!(e->ipv6.flags & IP6T_F_GOTO)) {
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+ if (unlikely(stackidx >= private->stacksize)) {
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+ verdict = NF_DROP;
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+ break;
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+ }
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jumpstack[stackidx++] = e;
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}
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--
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2.14.3
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