From: Pablo Neira Ayuso <pablo@netfilter.org>
To: netfilter-devel@vger.kernel.org
Cc: davem@davemloft.net, netdev@vger.kernel.org
Subject: [PATCH 3/5] netfilter: x_tables: Fix use-after-free in ipt_do_table.
Date: Thu, 24 Aug 2017 16:43:29 +0200 [thread overview]
Message-ID: <1503585811-13447-4-git-send-email-pablo@netfilter.org> (raw)
In-Reply-To: <1503585811-13447-1-git-send-email-pablo@netfilter.org>
From: Taehee Yoo <ap420073@gmail.com>
If verdict is NF_STOLEN in the SYNPROXY target,
the skb is consumed.
However, ipt_do_table() always tries to get ip header from the skb.
So that, KASAN triggers the use-after-free message.
We can reproduce this message using below command.
# iptables -I INPUT -p tcp -j SYNPROXY --mss 1460
[ 193.542265] BUG: KASAN: use-after-free in ipt_do_table+0x1405/0x1c10
[ ... ]
[ 193.578603] Call Trace:
[ 193.581590] <IRQ>
[ 193.584107] dump_stack+0x68/0xa0
[ 193.588168] print_address_description+0x78/0x290
[ 193.593828] ? ipt_do_table+0x1405/0x1c10
[ 193.598690] kasan_report+0x230/0x340
[ 193.603194] __asan_report_load2_noabort+0x19/0x20
[ 193.608950] ipt_do_table+0x1405/0x1c10
[ 193.613591] ? rcu_read_lock_held+0xae/0xd0
[ 193.618631] ? ip_route_input_rcu+0x27d7/0x4270
[ 193.624348] ? ipt_do_table+0xb68/0x1c10
[ 193.629124] ? do_add_counters+0x620/0x620
[ 193.634234] ? iptable_filter_net_init+0x60/0x60
[ ... ]
After this patch, only when verdict is XT_CONTINUE,
ipt_do_table() tries to get ip header.
Also arpt_do_table() is modified because it has same bug.
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
net/ipv4/netfilter/arp_tables.c | 10 +++++-----
net/ipv4/netfilter/ip_tables.c | 9 +++++----
2 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 0bc3c3d73e61..9e9d9afd18f7 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -268,14 +268,14 @@ unsigned int arpt_do_table(struct sk_buff *skb,
acpar.targinfo = t->data;
verdict = t->u.kernel.target->target(skb, &acpar);
- /* Target might have changed stuff. */
- arp = arp_hdr(skb);
-
- if (verdict == XT_CONTINUE)
+ if (verdict == XT_CONTINUE) {
+ /* Target might have changed stuff. */
+ arp = arp_hdr(skb);
e = arpt_next_entry(e);
- else
+ } else {
/* Verdict */
break;
+ }
} while (!acpar.hotdrop);
xt_write_recseq_end(addend);
local_bh_enable();
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 2a55a40211cb..622ed2887cd5 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -352,13 +352,14 @@ ipt_do_table(struct sk_buff *skb,
acpar.targinfo = t->data;
verdict = t->u.kernel.target->target(skb, &acpar);
- /* Target might have changed stuff. */
- ip = ip_hdr(skb);
- if (verdict == XT_CONTINUE)
+ if (verdict == XT_CONTINUE) {
+ /* Target might have changed stuff. */
+ ip = ip_hdr(skb);
e = ipt_next_entry(e);
- else
+ } else {
/* Verdict */
break;
+ }
} while (!acpar.hotdrop);
xt_write_recseq_end(addend);
--
2.1.4
next prev parent reply other threads:[~2017-08-24 14:43 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-24 14:43 [PATCH 0/5] Netfilter fixes for net Pablo Neira Ayuso
2017-08-24 14:43 ` [PATCH 1/5] netfilter: ipt_CLUSTERIP: fix use-after-free of proc entry Pablo Neira Ayuso
2017-08-24 14:43 ` [PATCH 2/5] netfilter: nft_compat: check extension hook mask only if set Pablo Neira Ayuso
2017-08-24 14:43 ` Pablo Neira Ayuso [this message]
2017-08-24 14:43 ` [PATCH 4/5] netfilter: check for seqadj ext existence before adding it in nf_nat_setup_info Pablo Neira Ayuso
2017-08-24 14:43 ` [PATCH 5/5] netfilter: nf_tables: Fix nft limit burst handling Pablo Neira Ayuso
2017-08-24 18:49 ` [PATCH 0/5] Netfilter fixes for net David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1503585811-13447-4-git-send-email-pablo@netfilter.org \
--to=pablo@netfilter.org \
--cc=davem@davemloft.net \
--cc=netdev@vger.kernel.org \
--cc=netfilter-devel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).