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netfilter: ipset: avoid null deref when IPSET_ATTR_LINENO is present 

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: a7b4f989a6 ("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>
This commit is contained in:
Florian Westphal 2020-01-08 10:59:38 +01:00 committed by Pablo Neira Ayuso
parent 1d9a7acd3d
commit 22dad713b8
1 changed files with 2 additions and 1 deletions
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3
net/netfilter/ipset/ip_set_core.c
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@ -1848,6 +1848,7 @@ static int ip_set_utest(struct net *net, struct sock *ctnl, struct sk_buff *skb,
struct ip_set *set;
struct nlattr *tb[IPSET_ATTR_ADT_MAX + 1] = {};
int ret = 0;
u32 lineno;
if (unlikely(protocol_min_failed(attr) ||
!attr[IPSET_ATTR_SETNAME] ||
@ -1864,7 +1865,7 @@ static int ip_set_utest(struct net *net, struct sock *ctnl, struct sk_buff *skb,
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)