[PATCH 1/7] net, smack: Create a function to set secmarks

[Casey Schaufler <casey@schaufler-ca.com>]

Rather than open coding assignments to skb->secmark, use a helper function
secxa_set_secmark(). This allows for a case where assigning a secmark
is more complex than a simple assignment. The version of the function
here does the legacy simple assignment.

Change the functions that currently assign values to skb->secmark to
use this function.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 include/linux/lsm_secxa.h        | 28 ++++++++++++++++++++++++++++
 net/netfilter/nft_meta.c         |  5 +++--
 net/netfilter/xt_CONNSECMARK.c   |  3 ++-
 net/netfilter/xt_SECMARK.c       |  3 ++-
 security/smack/smack_netfilter.c |  3 ++-
 5 files changed, 37 insertions(+), 5 deletions(-)
 create mode 100644 include/linux/lsm_secxa.h

diff --git a/include/linux/lsm_secxa.h b/include/linux/lsm_secxa.h
new file mode 100644
index 000000000000..926257d4730c
--- /dev/null
+++ b/include/linux/lsm_secxa.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (C) 2026 Casey Schaufler <casey@schaufler-ca.com>
+ */
+
+#ifndef __LINUX_LSM_SECXA_H
+#define __LINUX_LSM_SECXA_H
+
+#ifdef CONFIG_NETWORK_SECMARK
+
+#include <linux/security.h>
+#include <linux/skbuff.h>
+
+static inline void secxa_set_secmark(struct sk_buff *skb, u32 secxa)
+{
+	skb->secmark = secxa;
+}
+#else /* CONFIG_NETWORK_SECMARK */
+
+struct sk_buff;
+
+static inline void secxa_set_secmark(struct sk_buff *skb, u32 secxa)
+{
+}
+#endif /* CONFIG_NETWORK_SECMARK */
+
+#endif  /* __LINUX_LSM_SECXA_H */
diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
index 0a43e0787a68..bd0f7a0931f4 100644
--- a/net/netfilter/nft_meta.c
+++ b/net/netfilter/nft_meta.c
@@ -17,6 +17,7 @@
 #include <linux/random.h>
 #include <linux/smp.h>
 #include <linux/static_key.h>
+#include <linux/lsm_secxa.h>
 #include <net/dst.h>
 #include <net/ip.h>
 #include <net/sock.h>
@@ -502,7 +503,7 @@ void nft_meta_set_eval(const struct nft_expr *expr,
 		break;
 #ifdef CONFIG_NETWORK_SECMARK
 	case NFT_META_SECMARK:
-		skb->secmark = value;
+		secxa_set_secmark(skb, value);
 		break;
 #endif
 	default:
@@ -950,7 +951,7 @@ static void nft_secmark_obj_eval(struct nft_object *obj, struct nft_regs *regs,
 	const struct nft_secmark *priv = nft_obj_data(obj);
 	struct sk_buff *skb = pkt->skb;
 
-	skb->secmark = priv->secid;
+	secxa_set_secmark(skb, priv->secid);
 }
 
 static int nft_secmark_obj_init(const struct nft_ctx *ctx,
diff --git a/net/netfilter/xt_CONNSECMARK.c b/net/netfilter/xt_CONNSECMARK.c
index 1494b3ee30e1..9d799d2459dc 100644
--- a/net/netfilter/xt_CONNSECMARK.c
+++ b/net/netfilter/xt_CONNSECMARK.c
@@ -14,6 +14,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 #include <linux/module.h>
 #include <linux/skbuff.h>
+#include <linux/lsm_secxa.h>
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_CONNSECMARK.h>
 #include <net/netfilter/nf_conntrack.h>
@@ -55,7 +56,7 @@ static void secmark_restore(struct sk_buff *skb)
 
 		ct = nf_ct_get(skb, &ctinfo);
 		if (ct && ct->secmark)
-			skb->secmark = ct->secmark;
+			secxa_set_secmark(skb, ct->secmark);
 	}
 }
 
diff --git a/net/netfilter/xt_SECMARK.c b/net/netfilter/xt_SECMARK.c
index 5bc5ea505eb9..ea67aa92ddc2 100644
--- a/net/netfilter/xt_SECMARK.c
+++ b/net/netfilter/xt_SECMARK.c
@@ -11,6 +11,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 #include <linux/module.h>
 #include <linux/security.h>
+#include <linux/lsm_secxa.h>
 #include <linux/skbuff.h>
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_SECMARK.h>
@@ -36,7 +37,7 @@ secmark_tg(struct sk_buff *skb, const struct xt_secmark_target_info_v1 *info)
 		BUG();
 	}
 
-	skb->secmark = secmark;
+	secxa_set_secmark(skb, secmark);
 	return XT_CONTINUE;
 }
 
diff --git a/security/smack/smack_netfilter.c b/security/smack/smack_netfilter.c
index 17ba578b1308..b363c42f252e 100644
--- a/security/smack/smack_netfilter.c
+++ b/security/smack/smack_netfilter.c
@@ -14,6 +14,7 @@
 #include <linux/netfilter_ipv4.h>
 #include <linux/netfilter_ipv6.h>
 #include <linux/netdevice.h>
+#include <linux/lsm_secxa.h>
 #include <net/inet_sock.h>
 #include <net/net_namespace.h>
 #include "smack.h"
@@ -29,7 +30,7 @@ static unsigned int smack_ip_output(void *priv,
 	if (sk) {
 		ssp = smack_sock(sk);
 		skp = ssp->smk_out;
-		skb->secmark = skp->smk_secid;
+		secxa_set_secmark(skb, skp->smk_secid);
 	}
 
 	return NF_ACCEPT;
-- 
2.54.0