From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:34938 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754284AbeCPP2E (ORCPT ); Fri, 16 Mar 2018 11:28:04 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+e783f671527912cd9403@syzkaller.appspotmail.com, Florian Westphal , Pablo Neira Ayuso Subject: [PATCH 4.4 34/63] netfilter: add back stackpointer size checks Date: Fri, 16 Mar 2018 16:23:06 +0100 Message-Id: <20180316152303.772488841@linuxfoundation.org> In-Reply-To: <20180316152259.964532775@linuxfoundation.org> References: <20180316152259.964532775@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Florian Westphal 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 --- net/ipv4/netfilter/arp_tables.c | 4 ++++ net/ipv4/netfilter/ip_tables.c | 4 ++++ net/ipv6/netfilter/ip6_tables.c | 4 ++++ 3 files changed, 12 insertions(+) --- 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_buf } if (table_base + v != arpt_next_entry(e)) { + if (unlikely(stackidx >= private->stacksize)) { + verdict = NF_DROP; + break; + } jumpstack[stackidx++] = e; } --- 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); --- 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; }