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authorFlorian Westphal <fw@strlen.de>2018-02-07 13:46:25 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-15 10:56:56 +0100
commitec6b058c5431e7e1686c4d7ef42f951473baa78b (patch)
treecb4c55cdde7853ddc7f1acf0562130f07564c5ca
parent831b5146892e3719bb2d86fcf826b41e9e6f9ec1 (diff)
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. 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>
-rw-r--r--net/ipv4/netfilter/arp_tables.c4
-rw-r--r--net/ipv4/netfilter/ip_tables.c7
-rw-r--r--net/ipv6/netfilter/ip6_tables.c4
3 files changed, 14 insertions, 1 deletions
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 0c3c944a7b72..8e5185ad6310 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 2e0d339028bb..a74a81624983 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 1d7ae9366335..51f3bc632c7c 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;
}