From: Pablo Neira Ayuso <pablo@netfilter.org>
To: netfilter-devel@vger.kernel.org
Cc: fw@strlen.de
Subject: [PATCH nf 1/5] netfilter: nf_conntrack_expect: honor expectation helper field
Date: Fri, 20 Mar 2026 13:59:43 +0100 [thread overview]
Message-ID: <20260320125947.305117-2-pablo@netfilter.org> (raw)
In-Reply-To: <20260320125947.305117-1-pablo@netfilter.org>
The expectation helper field is mostly unused. As a result, the
netfilter codebase relies on accessing the helper through exp->master.
Always set on the expectation helper field so it can be used to reach
the helper.
This is a preparation patches for follow up fixes.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
include/net/netfilter/nf_conntrack_expect.h | 2 +-
net/netfilter/nf_conntrack_broadcast.c | 2 +-
net/netfilter/nf_conntrack_expect.c | 6 +++++-
net/netfilter/nf_conntrack_h323_main.c | 12 ++++++------
net/netfilter/nf_conntrack_helper.c | 5 +++++
net/netfilter/nf_conntrack_netlink.c | 2 +-
net/netfilter/nf_conntrack_sip.c | 2 +-
7 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/include/net/netfilter/nf_conntrack_expect.h b/include/net/netfilter/nf_conntrack_expect.h
index 165e7a03b8e9..1b01400b10bd 100644
--- a/include/net/netfilter/nf_conntrack_expect.h
+++ b/include/net/netfilter/nf_conntrack_expect.h
@@ -40,7 +40,7 @@ struct nf_conntrack_expect {
struct nf_conntrack_expect *this);
/* Helper to assign to new connection */
- struct nf_conntrack_helper *helper;
+ struct nf_conntrack_helper __rcu *helper;
/* The conntrack of the master connection */
struct nf_conn *master;
diff --git a/net/netfilter/nf_conntrack_broadcast.c b/net/netfilter/nf_conntrack_broadcast.c
index a7552a46d6ac..d21576fcb1d6 100644
--- a/net/netfilter/nf_conntrack_broadcast.c
+++ b/net/netfilter/nf_conntrack_broadcast.c
@@ -70,7 +70,7 @@ int nf_conntrack_broadcast_help(struct sk_buff *skb,
exp->expectfn = NULL;
exp->flags = NF_CT_EXPECT_PERMANENT;
exp->class = NF_CT_EXPECT_CLASS_DEFAULT;
- exp->helper = NULL;
+ rcu_assign_pointer(exp->helper, nfct_help(ct)->helper);
nf_ct_expect_related(exp, 0);
nf_ct_expect_put(exp);
diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index cfc2daa3fc7f..197a76d0b231 100644
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -309,6 +309,10 @@ struct nf_conntrack_expect *nf_ct_expect_alloc(struct nf_conn *me)
}
EXPORT_SYMBOL_GPL(nf_ct_expect_alloc);
+/* This function can only be used from packet path, where accessing
+ * master's helper is safe, because the packet holds a reference on
+ * the conntrack object. Never use it from control plane.
+ */
void nf_ct_expect_init(struct nf_conntrack_expect *exp, unsigned int class,
u_int8_t family,
const union nf_inet_addr *saddr,
@@ -325,7 +329,7 @@ void nf_ct_expect_init(struct nf_conntrack_expect *exp, unsigned int class,
exp->flags = 0;
exp->class = class;
exp->expectfn = NULL;
- exp->helper = NULL;
+ rcu_assign_pointer(exp->helper, nfct_help(exp->master)->helper);
exp->tuple.src.l3num = family;
exp->tuple.dst.protonum = proto;
diff --git a/net/netfilter/nf_conntrack_h323_main.c b/net/netfilter/nf_conntrack_h323_main.c
index a2a0e22ccee1..3f5c50455b71 100644
--- a/net/netfilter/nf_conntrack_h323_main.c
+++ b/net/netfilter/nf_conntrack_h323_main.c
@@ -643,7 +643,7 @@ static int expect_h245(struct sk_buff *skb, struct nf_conn *ct,
&ct->tuplehash[!dir].tuple.src.u3,
&ct->tuplehash[!dir].tuple.dst.u3,
IPPROTO_TCP, NULL, &port);
- exp->helper = &nf_conntrack_helper_h245;
+ rcu_assign_pointer(exp->helper, &nf_conntrack_helper_h245);
nathook = rcu_dereference(nfct_h323_nat_hook);
if (memcmp(&ct->tuplehash[dir].tuple.src.u3,
@@ -767,7 +767,7 @@ static int expect_callforwarding(struct sk_buff *skb,
nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct),
&ct->tuplehash[!dir].tuple.src.u3, &addr,
IPPROTO_TCP, NULL, &port);
- exp->helper = nf_conntrack_helper_q931;
+ rcu_assign_pointer(exp->helper, nf_conntrack_helper_q931);
nathook = rcu_dereference(nfct_h323_nat_hook);
if (memcmp(&ct->tuplehash[dir].tuple.src.u3,
@@ -1234,7 +1234,7 @@ static int expect_q931(struct sk_buff *skb, struct nf_conn *ct,
&ct->tuplehash[!dir].tuple.src.u3 : NULL,
&ct->tuplehash[!dir].tuple.dst.u3,
IPPROTO_TCP, NULL, &port);
- exp->helper = nf_conntrack_helper_q931;
+ rcu_assign_pointer(exp->helper, nf_conntrack_helper_q931);
exp->flags = NF_CT_EXPECT_PERMANENT; /* Accept multiple calls */
nathook = rcu_dereference(nfct_h323_nat_hook);
@@ -1306,7 +1306,7 @@ static int process_gcf(struct sk_buff *skb, struct nf_conn *ct,
nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct),
&ct->tuplehash[!dir].tuple.src.u3, &addr,
IPPROTO_UDP, NULL, &port);
- exp->helper = nf_conntrack_helper_ras;
+ rcu_assign_pointer(exp->helper, nf_conntrack_helper_ras);
if (nf_ct_expect_related(exp, 0) == 0) {
pr_debug("nf_ct_ras: expect RAS ");
@@ -1523,7 +1523,7 @@ static int process_acf(struct sk_buff *skb, struct nf_conn *ct,
&ct->tuplehash[!dir].tuple.src.u3, &addr,
IPPROTO_TCP, NULL, &port);
exp->flags = NF_CT_EXPECT_PERMANENT;
- exp->helper = nf_conntrack_helper_q931;
+ rcu_assign_pointer(exp->helper, nf_conntrack_helper_q931);
if (nf_ct_expect_related(exp, 0) == 0) {
pr_debug("nf_ct_ras: expect Q.931 ");
@@ -1577,7 +1577,7 @@ static int process_lcf(struct sk_buff *skb, struct nf_conn *ct,
&ct->tuplehash[!dir].tuple.src.u3, &addr,
IPPROTO_TCP, NULL, &port);
exp->flags = NF_CT_EXPECT_PERMANENT;
- exp->helper = nf_conntrack_helper_q931;
+ rcu_assign_pointer(exp->helper, nf_conntrack_helper_q931);
if (nf_ct_expect_related(exp, 0) == 0) {
pr_debug("nf_ct_ras: expect Q.931 ");
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index ceb48c3ca0a4..a4671f517200 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -421,6 +421,11 @@ void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
nf_ct_iterate_destroy(unhelp, me);
+
+ /* nf_ct_iterate_destroy() does an unconditional synchronize_rcu() as
+ * last step, this ensures rcu readers of exp->helper are done.
+ * No need for another synchronize_rcu() here.
+ */
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index c156574e1273..a42d14290786 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -3573,7 +3573,7 @@ ctnetlink_alloc_expect(const struct nlattr * const cda[], struct nf_conn *ct,
exp->class = class;
exp->master = ct;
- exp->helper = helper;
+ rcu_assign_pointer(exp->helper, helper);
exp->tuple = *tuple;
exp->mask.src.u3 = mask->src.u3;
exp->mask.src.u.all = mask->src.u.all;
diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index 4ab5ef71d96d..106b2f419e19 100644
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -1297,7 +1297,7 @@ static int process_register_request(struct sk_buff *skb, unsigned int protoff,
nf_ct_expect_init(exp, SIP_EXPECT_SIGNALLING, nf_ct_l3num(ct),
saddr, &daddr, proto, NULL, &port);
exp->timeout.expires = sip_timeout * HZ;
- exp->helper = helper;
+ rcu_assign_pointer(exp->helper, helper);
exp->flags = NF_CT_EXPECT_PERMANENT | NF_CT_EXPECT_INACTIVE;
hooks = rcu_dereference(nf_nat_sip_hooks);
--
2.47.3
next prev parent reply other threads:[~2026-03-20 12:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-20 12:59 [PATCH nf 0/5] conntrack expectation fixes Pablo Neira Ayuso
2026-03-20 12:59 ` Pablo Neira Ayuso [this message]
2026-03-20 12:59 ` [PATCH nf 2/5] netfilter: nf_conntrack_expect: use expect->helper Pablo Neira Ayuso
2026-03-20 12:59 ` [PATCH nf 3/5] netfilter: ctnetlink: ensure safe access to master conntrack Pablo Neira Ayuso
2026-03-20 12:59 ` [PATCH nf 4/5] netfilter: nf_conntrack_expect: store netns and zone in expectation Pablo Neira Ayuso
2026-03-20 13:16 ` Florian Westphal
2026-03-20 12:59 ` [PATCH nf 5/5] netfilter: nf_conntrack_expect: skip expectations in other netns via proc Pablo Neira Ayuso
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