diff options
| author | Florian Westphal <fw@strlen.de> | 2018-02-07 13:46:25 +0100 |
|---|---|---|
| committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2018-02-14 20:47:41 +0100 |
| commit | 57ebd808a97d7c5b1e1afb937c2db22beba3c1f8 (patch) | |
| tree | 8a048d1fd60cb33a795d292ab8eada5840826325 | |
| parent | 01ea306f2ac2baff98d472da719193e738759d93 (diff) | |
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.
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>
| -rw-r--r-- | net/ipv4/netfilter/arp_tables.c | 4 | ||||
| -rw-r--r-- | net/ipv4/netfilter/ip_tables.c | 7 | ||||
| -rw-r--r-- | net/ipv6/netfilter/ip6_tables.c | 4 |
3 files changed, 14 insertions, 1 deletions
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index 4ffe302f9b82..e3e420f3ba7b 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 9a71f3149507..e38395a8dcf2 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 af4c917e0836..62358b93bbac 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; } |