| 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: netfilter: add back stackpointer size checks |
| |
| From: Florian Westphal <fw@strlen.de> |
| |
| 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> |
| |
| --- |
| 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(-) |
| |
| --- 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_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 |
| @@ -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; |
| --- 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; |
| } |
| |