From: Florian Westphal Date: Wed, 7 Feb 2018 12:46:25 +0000 (+0100) Subject: netfilter: add back stackpointer size checks X-Git-Tag: v4.4.122~30 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=48db3004d40d97d3ac205d2d64ab580a8cfcfe63;p=thirdparty%2Fkernel%2Fstable.git 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 Signed-off-by: Pablo Neira Ayuso Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index 4cfcc22f7430d..c18f0554b87cd 100644 --- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -329,6 +329,10 @@ 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 a98173d1ea97a..0bcf906bc4fb6 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -408,6 +408,10 @@ ipt_do_table(struct sk_buff *skb, } if (table_base + v != ipt_next_entry(e) && !(e->ip.flags & IPT_F_GOTO)) { + if (unlikely(stackidx >= private->stacksize)) { + verdict = NF_DROP; + break; + } jumpstack[stackidx++] = e; pr_debug("Pushed %p into pos %u\n", e, stackidx - 1); diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c index bb1b5453a7a1e..32d64e023b892 100644 --- a/net/ipv6/netfilter/ip6_tables.c +++ b/net/ipv6/netfilter/ip6_tables.c @@ -425,6 +425,10 @@ 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; }