[PATCH 4.14 39/39] netfilter: ipset: avoid null deref when IPSET_ATTR_LINENO is present

Greg Kroah-Hartman
2020-01-14T10:10:38Z

From: Florian Westphal <fw@strlen.de>

commit 22dad713b8a5ff488e07b821195270672f486eb2 upstream.

The set uadt functions assume lineno is never NULL, but it is in
case of ip_set_utest().

syzkaller managed to generate a netlink message that calls this with
LINENO attr present:

general protection fault: 0000 [#1] PREEMPT SMP KASAN
RIP: 0010:hash_mac4_uadt+0x1bc/0x470 net/netfilter/ipset/ip_set_hash_mac.c:104
Call Trace:
ip_set_utest+0x55b/0x890 net/netfilter/ipset/ip_set_core.c:1867
nfnetlink_rcv_msg+0xcf2/0xfb0 net/netfilter/nfnetlink.c:229
netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
nfnetlink_rcv+0x1ba/0x460 net/netfilter/nfnetlink.c:563

pass a dummy lineno storage, its easier than patching all set
implementations.

This seems to be a day-0 bug.

Cc: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Reported-by: syzbot+34bd2369d38707f3f4a7@syzkaller.appspotmail.com
Fixes: a7b4f989a6294 ("netfilter: ipset: IP set core support")
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/netfilter/ipset/ip_set_core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/netfilter/ipset/ip_set_core.c
+++ b/net/netfilter/ipset/ip_set_core.c
@@ -1639,6 +1639,7 @@ static int ip_set_utest(struct net *net,
struct ip_set *set;
struct nlattr *tb[IPSET_ATTR_ADT_MAX + 1] = {};
int ret = 0;
+ u32 lineno;

if (unlikely(protocol_failed(attr) ||
!attr[IPSET_ATTR_SETNAME] ||
@@ -1655,7 +1656,7 @@ static int ip_set_utest(struct net *net,
return -IPSET_ERR_PROTOCOL;

rcu_read_lock_bh();
- ret = set->variant->uadt(set, tb, IPSET_TEST, NULL, 0, 0);
+ ret = set->variant->uadt(set, tb, IPSET_TEST, &lineno, 0, 0);
rcu_read_unlock_bh();
/* Userspace can't trigger element to be re-added */
if (ret == -EAGAIN)