[PATCH nf-next] netfilter: ctnetlink: remove refcounting in dying list dumping

[PATCH nf-next] netfilter: ctnetlink: remove refcounting in dying list dumping

[Florian Westphal]

There is no need to keep the object alive via refcount, use a cookie and
then use that as the skip hint for dump resumption.

Unlike the two earlier, similar changes to this file, this is a cleanup
without intended side effects.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_conntrack_netlink.c | 39 +++++++---------------------
 1 file changed, 10 insertions(+), 29 deletions(-)

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 486d52b45fe5..9f5ff7c92440 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -60,7 +60,7 @@ MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("List and change connection tracking table");
 
 struct ctnetlink_list_dump_ctx {
-	struct nf_conn *last;
+	unsigned long last_id;
 	unsigned int cpu;
 	bool done;
 };
@@ -1731,16 +1731,6 @@ static int ctnetlink_get_conntrack(struct sk_buff *skb,
 	return nfnetlink_unicast(skb2, info->net, NETLINK_CB(skb).portid);
 }
 
-static int ctnetlink_done_list(struct netlink_callback *cb)
-{
-	struct ctnetlink_list_dump_ctx *ctx = (void *)cb->ctx;
-
-	if (ctx->last)
-		nf_ct_put(ctx->last);
-
-	return 0;
-}
-
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
 static int ctnetlink_dump_one_entry(struct sk_buff *skb,
 				    struct netlink_callback *cb,
@@ -1755,11 +1745,11 @@ static int ctnetlink_dump_one_entry(struct sk_buff *skb,
 	if (l3proto && nf_ct_l3num(ct) != l3proto)
 		return 0;
 
-	if (ctx->last) {
-		if (ct != ctx->last)
+	if (ctx->last_id) {
+		if (ctnetlink_get_id(ct) != ctx->last_id)
 			return 0;
 
-		ctx->last = NULL;
+		ctx->last_id = 0;
 	}
 
 	/* We can't dump extension info for the unconfirmed
@@ -1773,12 +1763,8 @@ static int ctnetlink_dump_one_entry(struct sk_buff *skb,
 				  cb->nlh->nlmsg_seq,
 				  NFNL_MSG_TYPE(cb->nlh->nlmsg_type),
 				  ct, dying, 0);
-	if (res < 0) {
-		if (!refcount_inc_not_zero(&ct->ct_general.use))
-			return 0;
-
-		ctx->last = ct;
-	}
+	if (res < 0)
+		ctx->last_id = ctnetlink_get_id(ct);
 
 	return res;
 }
@@ -1794,7 +1780,7 @@ static int
 ctnetlink_dump_dying(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	struct ctnetlink_list_dump_ctx *ctx = (void *)cb->ctx;
-	struct nf_conn *last = ctx->last;
+	unsigned long last_id = ctx->last_id;
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
 	const struct net *net = sock_net(skb->sk);
 	struct nf_conntrack_net_ecache *ecache_net;
@@ -1805,7 +1791,7 @@ ctnetlink_dump_dying(struct sk_buff *skb, struct netlink_callback *cb)
 	if (ctx->done)
 		return 0;
 
-	ctx->last = NULL;
+	ctx->last_id = 0;
 
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
 	ecache_net = nf_conn_pernet_ecache(net);
@@ -1816,24 +1802,21 @@ ctnetlink_dump_dying(struct sk_buff *skb, struct netlink_callback *cb)
 		int res;
 
 		ct = nf_ct_tuplehash_to_ctrack(h);
-		if (last && last != ct)
+		if (last_id && last_id != ctnetlink_get_id(ct))
 			continue;
 
 		res = ctnetlink_dump_one_entry(skb, cb, ct, true);
 		if (res < 0) {
 			spin_unlock_bh(&ecache_net->dying_lock);
-			nf_ct_put(last);
 			return skb->len;
 		}
 
-		nf_ct_put(last);
-		last = NULL;
+		last_id = 0;
 	}
 
 	spin_unlock_bh(&ecache_net->dying_lock);
 #endif
 	ctx->done = true;
-	nf_ct_put(last);
 
 	return skb->len;
 }
@@ -1845,7 +1828,6 @@ static int ctnetlink_get_ct_dying(struct sk_buff *skb,
 	if (info->nlh->nlmsg_flags & NLM_F_DUMP) {
 		struct netlink_dump_control c = {
 			.dump = ctnetlink_dump_dying,
-			.done = ctnetlink_done_list,
 		};
 		return netlink_dump_start(info->sk, skb, info->nlh, &c);
 	}
@@ -1860,7 +1842,6 @@ static int ctnetlink_get_ct_unconfirmed(struct sk_buff *skb,
 	if (info->nlh->nlmsg_flags & NLM_F_DUMP) {
 		struct netlink_dump_control c = {
 			.dump = ctnetlink_dump_unconfirmed,
-			.done = ctnetlink_done_list,
 		};
 		return netlink_dump_start(info->sk, skb, info->nlh, &c);
 	}
-- 
2.49.1

Re: [PATCH nf-next] netfilter: ctnetlink: remove refcounting in dying list dumping

[kernel test robot]

Hi Florian,

kernel test robot noticed the following build warnings:

[auto build test WARNING on netfilter-nf/main]
[also build test WARNING on linus/master v6.17-rc1 next-20250814]
[cannot apply to nf-next/master]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Florian-Westphal/netfilter-ctnetlink-remove-refcounting-in-dying-list-dumping/20250815-003116
base:   https://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git main
patch link:    https://lore.kernel.org/r/20250814162307.26029-1-fw%40strlen.de
patch subject: [PATCH nf-next] netfilter: ctnetlink: remove refcounting in dying list dumping
config: hexagon-randconfig-001-20250815 (https://download.01.org/0day-ci/archive/20250815/202508151104.eDVcRAdD-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 3769ce013be2879bf0b329c14a16f5cb766f26ce)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250815/202508151104.eDVcRAdD-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508151104.eDVcRAdD-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> net/netfilter/nf_conntrack_netlink.c:1785:16: warning: unused variable 'last_id' [-Wunused-variable]
    1785 |         unsigned long last_id = ctx->last_id;
         |                       ^~~~~~~
   1 warning generated.


vim +/last_id +1785 net/netfilter/nf_conntrack_netlink.c

  1780	
  1781	static int
  1782	ctnetlink_dump_dying(struct sk_buff *skb, struct netlink_callback *cb)
  1783	{
  1784		struct ctnetlink_list_dump_ctx *ctx = (void *)cb->ctx;
> 1785		unsigned long last_id = ctx->last_id;
  1786	#ifdef CONFIG_NF_CONNTRACK_EVENTS
  1787		const struct net *net = sock_net(skb->sk);
  1788		struct nf_conntrack_net_ecache *ecache_net;
  1789		struct nf_conntrack_tuple_hash *h;
  1790		struct hlist_nulls_node *n;
  1791	#endif
  1792	
  1793		if (ctx->done)
  1794			return 0;
  1795	
  1796		ctx->last_id = 0;
  1797	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki