diff mbox series

[nf,v3,1/2] netfilter: nfnetlink_cthelper: use {READ,WRITE}_ONCE for accessing helper flags

Message ID 20260514153814.877747-1-pablo@netfilter.org
State Superseded, archived
Headers show
Series [nf,v3,1/2] netfilter: nfnetlink_cthelper: use {READ,WRITE}_ONCE for accessing helper flags | expand

Commit Message

Pablo Neira Ayuso May 14, 2026, 3:38 p.m. UTC 
Conntrack helper flags are accessed from packet and netlink dump path.
While updates are protected by the nfnl_mutex, use {READ,WRITE}_ONCE()
to access this flags.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
v3: new in this series, per Florian comment.

 net/netfilter/nfnetlink_cthelper.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/net/netfilter/nfnetlink_cthelper.c b/net/netfilter/nfnetlink_cthelper.c
index 0d16ad82d70c..34ac6af1e0dd 100644
--- a/net/netfilter/nfnetlink_cthelper.c
+++ b/net/netfilter/nfnetlink_cthelper.c
@@ -41,8 +41,9 @@  static int
 nfnl_userspace_cthelper(struct sk_buff *skb, unsigned int protoff,
 			struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 {
-	const struct nf_conn_help *help;
 	struct nf_conntrack_helper *helper;
+	const struct nf_conn_help *help;
+	unsigned int helper_flags;
 
 	help = nfct_help(ct);
 	if (help == NULL)
@@ -53,8 +54,10 @@  nfnl_userspace_cthelper(struct sk_buff *skb, unsigned int protoff,
 	if (helper == NULL)
 		return NF_DROP;
 
+	helper_flags = READ_ONCE(helper->flags);
+
 	/* This is a user-space helper not yet configured, skip. */
-	if ((helper->flags &
+	if ((helper_flags &
 	    (NF_CT_HELPER_F_USERSPACE | NF_CT_HELPER_F_CONFIGURED)) ==
 	     NF_CT_HELPER_F_USERSPACE)
 		return NF_ACCEPT;
@@ -404,10 +407,10 @@  nfnl_cthelper_update(const struct nlattr * const tb[],
 
 		switch(status) {
 		case NFCT_HELPER_STATUS_ENABLED:
-			helper->flags |= NF_CT_HELPER_F_CONFIGURED;
+			WRITE_ONCE(helper->flags, helper->flags | NF_CT_HELPER_F_CONFIGURED);
 			break;
 		case NFCT_HELPER_STATUS_DISABLED:
-			helper->flags &= ~NF_CT_HELPER_F_CONFIGURED;
+			WRITE_ONCE(helper->flags, helper->flags & ~NF_CT_HELPER_F_CONFIGURED);
 			break;
 		}
 	}
@@ -529,8 +532,8 @@  static int
 nfnl_cthelper_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
 			int event, struct nf_conntrack_helper *helper)
 {
+	unsigned int flags = portid ? NLM_F_MULTI : 0, helper_flags;
 	struct nlmsghdr *nlh;
-	unsigned int flags = portid ? NLM_F_MULTI : 0;
 	int status;
 
 	event = nfnl_msg_type(NFNL_SUBSYS_CTHELPER, event);
@@ -554,7 +557,8 @@  nfnl_cthelper_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
 	if (nla_put_be32(skb, NFCTH_PRIV_DATA_LEN, htonl(helper->data_len)))
 		goto nla_put_failure;
 
-	if (helper->flags & NF_CT_HELPER_F_CONFIGURED)
+	helper_flags = READ_ONCE(helper->flags);
+	if (helper_flags & NF_CT_HELPER_F_CONFIGURED)
 		status = NFCT_HELPER_STATUS_ENABLED;
 	else
 		status = NFCT_HELPER_STATUS_DISABLED;
@@ -575,6 +579,7 @@  static int
 nfnl_cthelper_dump_table(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	struct nf_conntrack_helper *cur, *last;
+	unsigned int helper_flags;
 
 	rcu_read_lock();
 	last = (struct nf_conntrack_helper *)cb->args[1];
@@ -583,8 +588,10 @@  nfnl_cthelper_dump_table(struct sk_buff *skb, struct netlink_callback *cb)
 		hlist_for_each_entry_rcu(cur,
 				&nf_ct_helper_hash[cb->args[0]], hnode) {
 
+			helper_flags = READ_ONCE(cur->flags);
+
 			/* skip non-userspace conntrack helpers. */
-			if (!(cur->flags & NF_CT_HELPER_F_USERSPACE))
+			if (!(helper_flags & NF_CT_HELPER_F_USERSPACE))
 				continue;
 
 			if (cb->args[1]) {