netdev - Re: [PATCH] ipset: fix a missing check of nla

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Message-ID: <298cbd2a-06fd-39c1-7d5f-5adcf21b68b2@virtuozzo.com>
Date:   Thu, 10 Jan 2019 11:54:01 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     Kangjie Lu <kjlu@....edu>, pakki001@....edu,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>,
        Stefano Brivio <sbrivio@...hat.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ipset: fix a missing check of nla_parse

On 10.01.2019 01:43, Pablo Neira Ayuso wrote:
> On Wed, Dec 26, 2018 at 12:16:25PM +0300, Kirill Tkhai wrote:
>> On 26.12.2018 06:50, Kangjie Lu wrote:
>>> When nla_parse fails, we should not use the results (the first
>>> argument). The fix checks if it fails, and if so, returns its error code
>>> upstream.
>>>
>>> Signed-off-by: Kangjie Lu <kjlu@....edu>
>>> ---
>>>  net/netfilter/ipset/ip_set_core.c | 4 +++-
>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
>>> index 1577f2f76060..4dc8057cff02 100644
>>> --- a/net/netfilter/ipset/ip_set_core.c
>>> +++ b/net/netfilter/ipset/ip_set_core.c
>>> @@ -1531,8 +1531,10 @@ call_ad(struct sock *ctnl, struct sk_buff *skb, struct ip_set *set,
>>>  		memcpy(&errmsg->msg, nlh, nlh->nlmsg_len);
>>>  		cmdattr = (void *)&errmsg->msg + min_len;
>>>  
>>> -		nla_parse(cda, IPSET_ATTR_CMD_MAX, cmdattr,
>>> +		ret = nla_parse(cda, IPSET_ATTR_CMD_MAX, cmdattr,
>>>  			  nlh->nlmsg_len - min_len, ip_set_adt_policy, NULL);
> 
> @Kangjie: nitpick, could you align this line below? ie.
> 
> 		ret = nla_parse(cda, IPSET_ATTR_CMD_MAX, cmdattr,
>                                 nlh->nlmsg_len - min_len, ip_set_adt_policy,
>                                 NULL);
> 
>>> +		if (ret)
>>> +			return ret;
>>
>> In this function above nlmsg_new() allocates skb2, but I don't see, where you free it here.
> 
> netlink_unicast() is responsible for releasing this skb2.

We return earlier at "if (ret)", so netlink_unicast() is not called.
 
>>>  		errline = nla_data(cda[IPSET_ATTR_LINENO]);

Kirill