diff --git a/config/kernel-namespace.m4 b/config/kernel-namespace.m4
new file mode 100644
index 000000000..9b0b12e4e
--- /dev/null
+++ b/config/kernel-namespace.m4
@@ -0,0 +1,31 @@
+dnl #
+dnl # 6.18 API change
+dnl # ns->ops->type was moved to ns->ns.ns_type (struct ns_common)
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_NS_COMMON_TYPE], [
+	ZFS_LINUX_TEST_SRC([ns_common_type], [
+		#include <linux/user_namespace.h>
+	],[
+		struct user_namespace ns;
+		ns.ns.ns_type = 0;
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_NS_COMMON_TYPE], [
+	AC_MSG_CHECKING([whether ns_type is accessible through ns_common])
+	ZFS_LINUX_TEST_RESULT([ns_common_type], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE([HAVE_NS_COMMON_TYPE], 1,
+			[Define if ns_type is accessible through ns_common])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_SRC_NAMESPACE], [
+	ZFS_AC_KERNEL_SRC_NS_COMMON_TYPE
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_NAMESPACE], [
+	ZFS_AC_KERNEL_NS_COMMON_TYPE
+])
diff --git a/config/kernel-userns-capabilities.m4 b/config/kernel-userns-capabilities.m4
deleted file mode 100644
index f4e24fb16..000000000
--- a/config/kernel-userns-capabilities.m4
+++ /dev/null
@@ -1,79 +0,0 @@
-dnl #
-dnl # 2.6.38 API change
-dnl # ns_capable() was introduced
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_SRC_NS_CAPABLE], [
-	ZFS_LINUX_TEST_SRC([ns_capable], [
-		#include <linux/capability.h>
-	],[
-		ns_capable((struct user_namespace *)NULL, CAP_SYS_ADMIN);
-	])
-])
-
-AC_DEFUN([ZFS_AC_KERNEL_NS_CAPABLE], [
-	AC_MSG_CHECKING([whether ns_capable exists])
-	ZFS_LINUX_TEST_RESULT([ns_capable], [
-		AC_MSG_RESULT(yes)
-	],[
-		ZFS_LINUX_TEST_ERROR([ns_capable()])
-	])
-])
-
-dnl #
-dnl # 2.6.39 API change
-dnl # struct user_namespace was added to struct cred_t as cred->user_ns member
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_SRC_CRED_USER_NS], [
-	ZFS_LINUX_TEST_SRC([cred_user_ns], [
-		#include <linux/cred.h>
-	],[
-		struct cred cr;
-		cr.user_ns = (struct user_namespace *)NULL;
-	])
-])
-
-AC_DEFUN([ZFS_AC_KERNEL_CRED_USER_NS], [
-	AC_MSG_CHECKING([whether cred_t->user_ns exists])
-	ZFS_LINUX_TEST_RESULT([cred_user_ns], [
-		AC_MSG_RESULT(yes)
-	],[
-		ZFS_LINUX_TEST_ERROR([cred_t->user_ns()])
-	])
-])
-
-dnl #
-dnl # 3.4 API change
-dnl # kuid_has_mapping() and kgid_has_mapping() were added to distinguish
-dnl # between internal kernel uids/gids and user namespace uids/gids.
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_SRC_KUID_HAS_MAPPING], [
-	ZFS_LINUX_TEST_SRC([kuid_has_mapping], [
-		#include <linux/uidgid.h>
-	],[
-		kuid_has_mapping((struct user_namespace *)NULL, KUIDT_INIT(0));
-		kgid_has_mapping((struct user_namespace *)NULL, KGIDT_INIT(0));
-	])
-])
-
-AC_DEFUN([ZFS_AC_KERNEL_KUID_HAS_MAPPING], [
-	AC_MSG_CHECKING([whether kuid_has_mapping/kgid_has_mapping exist])
-	ZFS_LINUX_TEST_RESULT([kuid_has_mapping], [
-		AC_MSG_RESULT(yes)
-	],[
-		ZFS_LINUX_TEST_ERROR([kuid_has_mapping()])
-	])
-])
-
-AC_DEFUN([ZFS_AC_KERNEL_SRC_USERNS_CAPABILITIES], [
-	ZFS_AC_KERNEL_SRC_NS_CAPABLE
-	ZFS_AC_KERNEL_SRC_HAS_CAPABILITY
-	ZFS_AC_KERNEL_SRC_CRED_USER_NS
-	ZFS_AC_KERNEL_SRC_KUID_HAS_MAPPING
-])
-
-AC_DEFUN([ZFS_AC_KERNEL_USERNS_CAPABILITIES], [
-	ZFS_AC_KERNEL_NS_CAPABLE
-	ZFS_AC_KERNEL_HAS_CAPABILITY
-	ZFS_AC_KERNEL_CRED_USER_NS
-	ZFS_AC_KERNEL_KUID_HAS_MAPPING
-])
diff --git a/config/kernel.m4 b/config/kernel.m4
index 27fe76616..8484bcfb1 100644
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -136,6 +136,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_TIMER
 	ZFS_AC_KERNEL_SRC_SUPER_BLOCK_S_WB_ERR
 	ZFS_AC_KERNEL_SRC_SOPS_FREE_INODE
+	ZFS_AC_KERNEL_SRC_NAMESPACE
 	case "$host_cpu" in
 		powerpc*)
 			ZFS_AC_KERNEL_SRC_CPU_HAS_FEATURE
@@ -256,6 +257,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_TIMER
 	ZFS_AC_KERNEL_SUPER_BLOCK_S_WB_ERR
 	ZFS_AC_KERNEL_SOPS_FREE_INODE
+	ZFS_AC_KERNEL_NAMESPACE
 	case "$host_cpu" in
 		powerpc*)
 			ZFS_AC_KERNEL_CPU_HAS_FEATURE
diff --git a/module/os/linux/spl/spl-zone.c b/module/os/linux/spl/spl-zone.c
index 45c2999a4..b2eae5d00 100644
--- a/module/os/linux/spl/spl-zone.c
+++ b/module/os/linux/spl/spl-zone.c
@@ -25,6 +25,10 @@
  * SUCH DAMAGE.
  */
 
+/*
+ * Copyright (c) 2025, Rob Norris <robn@despairlabs.com>
+ */
+
 #include <sys/types.h>
 #include <sys/sysmacros.h>
 #include <sys/kmem.h>
@@ -56,6 +60,19 @@ typedef struct zone_dataset {
 } zone_dataset_t;
 
 #ifdef CONFIG_USER_NS
+
+/*
+ * Linux 6.18 moved the generic namespace type away from ns->ops->type onto
+ * ns_common itself.
+ */
+#ifdef HAVE_NS_COMMON_TYPE
+#define	ns_is_newuser(ns)	\
+	((ns)->ns_type == CLONE_NEWUSER)
+#else
+#define	ns_is_newuser(ns)	\
+	((ns)->ops != NULL && (ns)->ops->type == CLONE_NEWUSER)
+#endif
+
 /*
  * Returns:
  * - 0 on success
@@ -84,7 +101,7 @@ user_ns_get(int fd, struct user_namespace **userns)
 		goto done;
 	}
 	ns = get_proc_ns(file_inode(nsfile));
-	if (ns->ops->type != CLONE_NEWUSER) {
+	if (!ns_is_newuser(ns)) {
 		error = ENOTTY;
 		goto done;
 	}