diff options
| author | Taehee Yoo <ap420073@gmail.com> | 2017-07-27 11:22:04 +0900 |
|---|---|---|
| committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2017-07-31 20:24:09 +0200 |
| commit | 9beceb54fa2c0b47532dd2b07f37e410641cf9b2 (patch) | |
| tree | 1da112b3fe8318d6a559617366ad591b411a00b3 /net/ipv4/netfilter/arp_tables.c | |
| parent | f7fb77fc12352d15180dc3c08ffba10573d5167d (diff) | |
netfilter: x_tables: Fix use-after-free in ipt_do_table.
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>
Diffstat (limited to 'net/ipv4/netfilter/arp_tables.c')
| -rw-r--r-- | net/ipv4/netfilter/arp_tables.c | 10 |
1 files changed, 5 insertions, 5 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(); |