netdev - Re: [PATCH] netfilter: ipset: ipset list may return wrong member count for set with timeout

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Date:   Mon, 11 Sep 2017 15:57:35 -0400
From:   Vishwanath Pai <vpai@...mai.com>
To:     Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>, johunt@...mai.com,
        pai.vishwain@...il.com, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, netdev@...r.kernel.org
Subject: Re: [PATCH] netfilter: ipset: ipset list may return wrong member
 count for set with timeout

Hi Jozsef,

Thank you. Yes, that is true, the count can still be incorrect in the
case of a huge set.

Thanks,
Vishwanath

On 09/11/2017 03:36 PM, Jozsef Kadlecsik wrote:
> Hi,
> 
> Your patch is applied in the ipset git tree and I'm going to push it for 
> kernel inclusion.
> 
> I modified the comment part: the elements counter can still be incorrect 
> in the case of a huge set, because elements might time out during the 
> listing.
> 
> Thanks for your patience!
> 
> Best regards,
> Jozsef
> 
> On Thu, 17 Aug 2017, Vishwanath Pai wrote:
> 
>> Simple testcase:
>>
>> $ ipset create test hash:ip timeout 5
>> $ ipset add test 1.2.3.4
>> $ ipset add test 1.2.2.2
>> $ sleep 5
>>
>> $ ipset l
>> Name: test
>> Type: hash:ip
>> Revision: 5
>> Header: family inet hashsize 1024 maxelem 65536 timeout 5
>> Size in memory: 296
>> References: 0
>> Number of entries: 2
>> Members:
>>
>> We return "Number of entries: 2" but no members are listed. That is
>> because mtype_list runs "ip_set_timeout_expired" and does not list the
>> expired entries, but set->elements is never upated (until mtype_gc
>> cleans it up later).
>>
>> Reviewed-by: Joshua Hunt <johunt@...mai.com>
>> Signed-off-by: Vishwanath Pai <vpai@...mai.com>
>> ---
>>  net/netfilter/ipset/ip_set_hash_gen.h | 12 +++++++++++-
>>  1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/netfilter/ipset/ip_set_hash_gen.h b/net/netfilter/ipset/ip_set_hash_gen.h
>> index f236c0b..ff3d31c 100644
>> --- a/net/netfilter/ipset/ip_set_hash_gen.h
>> +++ b/net/netfilter/ipset/ip_set_hash_gen.h
>> @@ -1041,12 +1041,22 @@ struct htype {
>>  static int
>>  mtype_head(struct ip_set *set, struct sk_buff *skb)
>>  {
>> -	const struct htype *h = set->data;
>> +	struct htype *h = set->data;
>>  	const struct htable *t;
>>  	struct nlattr *nested;
>>  	size_t memsize;
>>  	u8 htable_bits;
>>  
>> +	/* If any members have expired, set->elements will be wrong
>> +	 * mytype_expire function will update it with the right count.
>> +	 * we do not hold set->lock here, so grab it first.
>> +	 */
>> +	if (SET_WITH_TIMEOUT(set)) {
>> +		spin_lock_bh(&set->lock);
>> +		mtype_expire(set, h);
>> +		spin_unlock_bh(&set->lock);
>> +	}
>> +
>>  	rcu_read_lock_bh();
>>  	t = rcu_dereference_bh_nfnl(h->table);
>>  	memsize = mtype_ahash_memsize(h, t) + set->ext_size;
>> -- 
>> 1.9.1
>>
>>
> 
> -
> E-mail  : kadlec@...ckhole.kfki.hu, kadlecsik.jozsef@...ner.mta.hu
> PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
> Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
>           H-1525 Budapest 114, POB. 49, Hungary
>