netfilter: CVE-2018-1065

netfilter: add back stackpointer size checks

Reference:
https://nvd.nist.gov/vuln/detail/CVE-2018-1065
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=638c2e4eff89aae86593e80ac2be01eee195fccb

Change-Id: Id89654b8f9d92a644bd60410953a79e69341db7e
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

1 files changed, 91 insertions, 0 deletions

diff --git a/patches/cve/CVE-2018-1065-netfilter-add-back-stackpointer-size-checks.patch b/patches/cve/CVE-2018-1065-netfilter-add-back-stackpointer-size-checks.patch
new file mode 100644
index 0000000..6772178
--- /dev/null
+++ b/patches/cve/CVE-2018-1065-netfilter-add-back-stackpointer-size-checks.patch
@@ -0,0 +1,91 @@
+From 638c2e4eff89aae86593e80ac2be01eee195fccb Mon Sep 17 00:00:00 2001
+From: Florian Westphal <fw@strlen.de>
+Date: Wed, 7 Feb 2018 13:46:25 +0100
+Subject: [PATCH] netfilter: add back stackpointer size checks
+
+commit 57ebd808a97d7c5b1e1afb937c2db22beba3c1f8 upstream.
+
+The rationale for removing the check is only correct for rulesets
+generated by ip(6)tables.
+
+In iptables, a jump can only occur to a user-defined chain, i.e.
+because we size the stack based on number of user-defined chains we
+cannot exceed stack size.
+
+However, the underlying binary format has no such restriction,
+and the validation step only ensures that the jump target is a
+valid rule start point.
+
+IOW, its possible to build a rule blob that has no user-defined
+chains but does contain a jump.
+
+If this happens, no jump stack gets allocated and crash occurs
+because no jumpstack was allocated.
+
+CVE: CVE-2018-1065
+Upstream-Status: Backport [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=638c2e4eff89aae86593e80ac2be01eee195fccb]
+
+Fixes: 7814b6ec6d0d6 ("netfilter: xtables: don't save/restore jumpstack offset")
+Reported-by: syzbot+e783f671527912cd9403@syzkaller.appspotmail.com
+Signed-off-by: Florian Westphal <fw@strlen.de>
+Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
+---
+ net/ipv4/netfilter/arp_tables.c | 4 ++++
+ net/ipv4/netfilter/ip_tables.c  | 7 ++++++-
+ net/ipv6/netfilter/ip6_tables.c | 4 ++++
+ 3 files changed, 14 insertions(+), 1 deletion(-)
+
+diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
+index 9e2770fd00be..aa4c3b7f7da4 100644
+--- a/net/ipv4/netfilter/arp_tables.c
++++ b/net/ipv4/netfilter/arp_tables.c
+@@ -257,6 +257,10 @@ unsigned int arpt_do_table(struct sk_buff *skb,
+                        }
+                        if (table_base + v
+                            != arpt_next_entry(e)) {
++                               if (unlikely(stackidx >= private->stacksize)) {
++                                       verdict = NF_DROP;
++                                       break;
++                               }
+                                jumpstack[stackidx++] = e;
+                        }
+ 
+diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
+index 39286e543ee6..cadb82a906b8 100644
+--- a/net/ipv4/netfilter/ip_tables.c
++++ b/net/ipv4/netfilter/ip_tables.c
+@@ -335,8 +335,13 @@ ipt_do_table(struct sk_buff *skb,
+                                continue;
+                        }
+                        if (table_base + v != ipt_next_entry(e) &&
+-                           !(e->ip.flags & IPT_F_GOTO))
++                           !(e->ip.flags & IPT_F_GOTO)) {
++                               if (unlikely(stackidx >= private->stacksize)) {
++                                       verdict = NF_DROP;
++                                       break;
++                               }
+                                jumpstack[stackidx++] = e;
++                       }
+ 
+                        e = get_entry(table_base, v);
+                        continue;
+diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
+index 01bd3ee5ebc6..a0a31972fc75 100644
+--- a/net/ipv6/netfilter/ip6_tables.c
++++ b/net/ipv6/netfilter/ip6_tables.c
+@@ -357,6 +357,10 @@ ip6t_do_table(struct sk_buff *skb,
+                        }
+                        if (table_base + v != ip6t_next_entry(e) &&
+                            !(e->ipv6.flags & IP6T_F_GOTO)) {
++                               if (unlikely(stackidx >= private->stacksize)) {
++                                       verdict = NF_DROP;
++                                       break;
++                               }
+                                jumpstack[stackidx++] = e;
+                        }
+ 
+-- 
+2.20.1
+