netfilter: CVE-2018-1065

netfilter: add back stackpointer size checks

References:
https://github.com/torvalds/linux/commit/57ebd808a97d7c5b1e1afb937c2db22beba3c1f8

Change-Id: I5ee1c9b8036563602332c41163740dbc90a294fd
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

2 files changed, 91 insertions, 0 deletions

diff --git a/patches/cve/4.9.x.scc b/patches/cve/4.9.x.scc
index 96b6bcd..fd6f5c7 100644
--- a/patches/cve/4.9.x.scc
+++ b/patches/cve/4.9.x.scc
@@ -1,3 +1,6 @@
 #CVEs fixed in 4.9.82:
 patch CVE-2017-18344-posix-timer-Properly-check-sigevent-sigev_notify.patch
 patch CVE-2017-8824-dccp-CVE-2017-8824-use-after-free-in-DCCP-code.patch
+
+#CVEs fixed in 4.9.88:
+patch CVE-2018-1065-netfilter-add-back-stackpointer-size-checks.patch
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..5dc21e3
--- /dev/null
+++ b/patches/cve/CVE-2018-1065-netfilter-add-back-stackpointer-size-checks.patch
@@ -0,0 +1,88 @@
+From 57ebd808a97d7c5b1e1afb937c2db22beba3c1f8 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
+
+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  
+
+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: 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 4ffe302..e3e420f 100644
+--- a/net/ipv4/netfilter/arp_tables.c
++++ b/net/ipv4/netfilter/arp_tables.c
+@@ -252,6 +252,10 @@ 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 9a71f31..e38395a 100644
+--- a/net/ipv4/netfilter/ip_tables.c
++++ b/net/ipv4/netfilter/ip_tables.c
+@@ -330,8 +330,13 @@ 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 af4c917..62358b9 100644
+--- a/net/ipv6/netfilter/ip6_tables.c
++++ b/net/ipv6/netfilter/ip6_tables.c
+@@ -352,6 +352,10 @@ 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;
+                        }
+ 
+-- 
+
+