Re: [PATCH] netfilter: extend CONFIG_NF_CONNTRACK compile time checks

[Tom Rix <trix@redhat.com>]

On 1/11/22 1:46 AM, Pablo Neira Ayuso wrote:
> Hi,
>
> On Sat, Dec 25, 2021 at 09:37:44AM -0800, trix@redhat.com wrote:
>> From: Tom Rix <trix@redhat.com>
>>
>> Extends
>> commit 83ace77f5117 ("netfilter: ctnetlink: remove get_ct indirection")
>>
>> Add some compile time checks by following the ct and ctinfo variables
>> that are only set when CONFIG_NF_CONNTRACK is enabled.
>>
>> In nfulnl_log_packet(), ct is only set when CONFIG_NF_CONNTRACK
>> is enabled. ct's later use in __build_packet_message() is only
>> meaningful when CONFIG_NF_CONNTRACK is enabled, so add a check.
>>
>> In nfqnl_build_packet_message(), ct and ctinfo are only set when
>> CONFIG_NF_CONNTRACK is enabled.  Add a check for their decl and use.
>>
>> nfqnl_ct_parse() is a static function, move the check to the whole
>> function.
>>
>> In nfqa_parse_bridge(), ct and ctinfo are only set by the only
>> call to nfqnl_ct_parse(), so add a check for their decl and use.
>>
>> Consistently initialize ctinfo to 0.
> Are compile warning being trigger without this patch, maybe with
> CONFIG_NF_CONNTRACK=n?

No compiler warnings, this was found by visual inspection.

Robot says to entend more, so I want to make sure a human is also 
interested.

Tom

>
>> Signed-off-by: Tom Rix <trix@redhat.com>
>> ---
>>   net/netfilter/nfnetlink_log.c   |  4 +++-
>>   net/netfilter/nfnetlink_queue.c | 18 +++++++++++++-----
>>   2 files changed, 16 insertions(+), 6 deletions(-)
>>
>> diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
>> index ae9c0756bba59..e79d152184b71 100644
>> --- a/net/netfilter/nfnetlink_log.c
>> +++ b/net/netfilter/nfnetlink_log.c
>> @@ -627,9 +627,11 @@ __build_packet_message(struct nfnl_log_net *log,
>>   			 htonl(atomic_inc_return(&log->global_seq))))
>>   		goto nla_put_failure;
>>   
>> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>>   	if (ct && nfnl_ct->build(inst->skb, ct, ctinfo,
>>   				 NFULA_CT, NFULA_CT_INFO) < 0)
>>   		goto nla_put_failure;
>> +#endif
>>   
>>   	if ((pf == NFPROTO_NETDEV || pf == NFPROTO_BRIDGE) &&
>>   	    nfulnl_put_bridge(inst, skb) < 0)
>> @@ -689,7 +691,7 @@ nfulnl_log_packet(struct net *net,
>>   	struct nfnl_log_net *log = nfnl_log_pernet(net);
>>   	const struct nfnl_ct_hook *nfnl_ct = NULL;
>>   	struct nf_conn *ct = NULL;
>> -	enum ip_conntrack_info ctinfo;
>> +	enum ip_conntrack_info ctinfo = 0;
>>   
>>   	if (li_user && li_user->type == NF_LOG_TYPE_ULOG)
>>   		li = li_user;
>> diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
>> index 44c3de176d186..d59cae7561bf8 100644
>> --- a/net/netfilter/nfnetlink_queue.c
>> +++ b/net/netfilter/nfnetlink_queue.c
>> @@ -386,8 +386,10 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
>>   	struct sk_buff *entskb = entry->skb;
>>   	struct net_device *indev;
>>   	struct net_device *outdev;
>> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>>   	struct nf_conn *ct = NULL;
>>   	enum ip_conntrack_info ctinfo = 0;
>> +#endif
>>   	struct nfnl_ct_hook *nfnl_ct;
>>   	bool csum_verify;
>>   	char *secdata = NULL;
>> @@ -595,8 +597,10 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
>>   	if (seclen && nla_put(skb, NFQA_SECCTX, seclen, secdata))
>>   		goto nla_put_failure;
>>   
>> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>>   	if (ct && nfnl_ct->build(skb, ct, ctinfo, NFQA_CT, NFQA_CT_INFO) < 0)
>>   		goto nla_put_failure;
>> +#endif
>>   
>>   	if (cap_len > data_len &&
>>   	    nla_put_be32(skb, NFQA_CAP_LEN, htonl(cap_len)))
>> @@ -1104,13 +1108,13 @@ static int nfqnl_recv_verdict_batch(struct sk_buff *skb,
>>   	return 0;
>>   }
>>   
>> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>>   static struct nf_conn *nfqnl_ct_parse(struct nfnl_ct_hook *nfnl_ct,
>>   				      const struct nlmsghdr *nlh,
>>   				      const struct nlattr * const nfqa[],
>>   				      struct nf_queue_entry *entry,
>>   				      enum ip_conntrack_info *ctinfo)
>>   {
>> -#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>>   	struct nf_conn *ct;
>>   
>>   	ct = nf_ct_get(entry->skb, ctinfo);
>> @@ -1125,10 +1129,8 @@ static struct nf_conn *nfqnl_ct_parse(struct nfnl_ct_hook *nfnl_ct,
>>   				      NETLINK_CB(entry->skb).portid,
>>   				      nlmsg_report(nlh));
>>   	return ct;
>> -#else
>> -	return NULL;
>> -#endif
>>   }
>> +#endif
>>   
>>   static int nfqa_parse_bridge(struct nf_queue_entry *entry,
>>   			     const struct nlattr * const nfqa[])
>> @@ -1172,11 +1174,13 @@ static int nfqnl_recv_verdict(struct sk_buff *skb, const struct nfnl_info *info,
>>   	struct nfnl_queue_net *q = nfnl_queue_pernet(info->net);
>>   	u_int16_t queue_num = ntohs(info->nfmsg->res_id);
>>   	struct nfqnl_msg_verdict_hdr *vhdr;
>> -	enum ip_conntrack_info ctinfo;
>>   	struct nfqnl_instance *queue;
>>   	struct nf_queue_entry *entry;
>>   	struct nfnl_ct_hook *nfnl_ct;
>> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>>   	struct nf_conn *ct = NULL;
>> +	enum ip_conntrack_info ctinfo = 0;
>> +#endif
>>   	unsigned int verdict;
>>   	int err;
>>   
>> @@ -1198,11 +1202,13 @@ static int nfqnl_recv_verdict(struct sk_buff *skb, const struct nfnl_info *info,
>>   	/* rcu lock already held from nfnl->call_rcu. */
>>   	nfnl_ct = rcu_dereference(nfnl_ct_hook);
>>   
>> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>>   	if (nfqa[NFQA_CT]) {
>>   		if (nfnl_ct != NULL)
>>   			ct = nfqnl_ct_parse(nfnl_ct, info->nlh, nfqa, entry,
>>   					    &ctinfo);
>>   	}
>> +#endif
>>   
>>   	if (entry->state.pf == PF_BRIDGE) {
>>   		err = nfqa_parse_bridge(entry, nfqa);
>> @@ -1218,8 +1224,10 @@ static int nfqnl_recv_verdict(struct sk_buff *skb, const struct nfnl_info *info,
>>   				 payload_len, entry, diff) < 0)
>>   			verdict = NF_DROP;
>>   
>> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>>   		if (ct && diff)
>>   			nfnl_ct->seq_adjust(entry->skb, ct, ctinfo, diff);
>> +#endif
>>   	}
>>   
>>   	if (nfqa[NFQA_MARK])
>> -- 
>> 2.26.3
>>