Merge patch series "ns: tweak ns common handling"

Christian Brauner <brauner@kernel.org> says:

This contains three minor tweaks for namespace handling:

* Make struct ns_tree private. There's no need for anything to access
  that directly.

* Drop a debug assert that would trigger in conditions that are benign.

* Move the type of the namespace out of struct proc_ns_operations and
  into struct ns_common. This eliminates a pointer dereference and also
  allows assertions to work when the namespace type is disabled and the
  operations field set to NULL.

* patches from https://lore.kernel.org/20250924-work-namespaces-fixes-v1-0-8fb682c8678e@kernel.org:
  ns: drop assert
  ns: move ns type into struct ns_common
  nstree: make struct ns_tree private

Signed-off-by: Christian Brauner <brauner@kernel.org>

11 files changed, 27 insertions, 17 deletions

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 245b43ff2fa4..9b75102e81cb 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -224,6 +224,7 @@ struct cgroup_namespace init_cgroup_ns = {
 	.ns.ops		= &cgroupns_operations,
 	.ns.inum	= ns_init_inum(&init_cgroup_ns),
 	.root_cset	= &init_css_set,
+	.ns.ns_type	= ns_common_type(&init_cgroup_ns),
 };
 
 static struct file_system_type cgroup2_fs_type;
diff --git a/kernel/cgroup/namespace.c b/kernel/cgroup/namespace.c
index 04c98338ac08..241ca05f07c8 100644
--- a/kernel/cgroup/namespace.c
+++ b/kernel/cgroup/namespace.c
@@ -137,7 +137,6 @@ static struct user_namespace *cgroupns_owner(struct ns_common *ns)
 
 const struct proc_ns_operations cgroupns_operations = {
 	.name		= "cgroup",
-	.type		= CLONE_NEWCGROUP,
 	.get		= cgroupns_get,
 	.put		= cgroupns_put,
 	.install	= cgroupns_install,
diff --git a/kernel/nscommon.c b/kernel/nscommon.c
index 3cef89ddef41..c1fb2bad6d72 100644
--- a/kernel/nscommon.c
+++ b/kernel/nscommon.c
@@ -7,7 +7,7 @@
 #ifdef CONFIG_DEBUG_VFS
 static void ns_debug(struct ns_common *ns, const struct proc_ns_operations *ops)
 {
-	switch (ns->ops->type) {
+	switch (ns->ns_type) {
 #ifdef CONFIG_CGROUPS
 	case CLONE_NEWCGROUP:
 		VFS_WARN_ON_ONCE(ops != &cgroupns_operations);
@@ -46,18 +46,17 @@ static void ns_debug(struct ns_common *ns, const struct proc_ns_operations *ops)
 		VFS_WARN_ON_ONCE(ops != &utsns_operations);
 		break;
 #endif
-	default:
-		VFS_WARN_ON_ONCE(true);
 	}
 }
 #endif
 
-int __ns_common_init(struct ns_common *ns, const struct proc_ns_operations *ops, int inum)
+int __ns_common_init(struct ns_common *ns, u32 ns_type, const struct proc_ns_operations *ops, int inum)
 {
 	refcount_set(&ns->__ns_ref, 1);
 	ns->stashed = NULL;
 	ns->ops = ops;
 	ns->ns_id = 0;
+	ns->ns_type = ns_type;
 	RB_CLEAR_NODE(&ns->ns_tree_node);
 	INIT_LIST_HEAD(&ns->ns_list_node);
 
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 5f31fdff8a38..8d62449237b6 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -545,9 +545,9 @@ SYSCALL_DEFINE2(setns, int, fd, int, flags)
 
 	if (proc_ns_file(fd_file(f))) {
 		ns = get_proc_ns(file_inode(fd_file(f)));
-		if (flags && (ns->ops->type != flags))
+		if (flags && (ns->ns_type != flags))
 			err = -EINVAL;
-		flags = ns->ops->type;
+		flags = ns->ns_type;
 	} else if (!IS_ERR(pidfd_pid(fd_file(f)))) {
 		err = check_setns_flags(flags);
 	} else {
diff --git a/kernel/nstree.c b/kernel/nstree.c
index bbe8bedc924c..b24a320a11a6 100644
--- a/kernel/nstree.c
+++ b/kernel/nstree.c
@@ -4,6 +4,20 @@
 #include <linux/proc_ns.h>
 #include <linux/vfsdebug.h>
 
+/**
+ * struct ns_tree - Namespace tree
+ * @ns_tree: Rbtree of namespaces of a particular type
+ * @ns_list: Sequentially walkable list of all namespaces of this type
+ * @ns_tree_lock: Seqlock to protect the tree and list
+ * @type: type of namespaces in this tree
+ */
+struct ns_tree {
+       struct rb_root ns_tree;
+       struct list_head ns_list;
+       seqlock_t ns_tree_lock;
+       int type;
+};
+
 struct ns_tree mnt_ns_tree = {
 	.ns_tree = RB_ROOT,
 	.ns_list = LIST_HEAD_INIT(mnt_ns_tree.ns_list),
@@ -92,7 +106,7 @@ void __ns_tree_add_raw(struct ns_common *ns, struct ns_tree *ns_tree)
 
 	write_seqlock(&ns_tree->ns_tree_lock);
 
-	VFS_WARN_ON_ONCE(ns->ops->type != ns_tree->type);
+	VFS_WARN_ON_ONCE(ns->ns_type != ns_tree->type);
 
 	node = rb_find_add_rcu(&ns->ns_tree_node, &ns_tree->ns_tree, ns_cmp);
 	/*
@@ -114,7 +128,7 @@ void __ns_tree_remove(struct ns_common *ns, struct ns_tree *ns_tree)
 {
 	VFS_WARN_ON_ONCE(RB_EMPTY_NODE(&ns->ns_tree_node));
 	VFS_WARN_ON_ONCE(list_empty(&ns->ns_list_node));
-	VFS_WARN_ON_ONCE(ns->ops->type != ns_tree->type);
+	VFS_WARN_ON_ONCE(ns->ns_type != ns_tree->type);
 
 	write_seqlock(&ns_tree->ns_tree_lock);
 	rb_erase(&ns->ns_tree_node, &ns_tree->ns_tree);
@@ -183,7 +197,7 @@ struct ns_common *ns_tree_lookup_rcu(u64 ns_id, int ns_type)
 	if (!node)
 		return NULL;
 
-	VFS_WARN_ON_ONCE(node_to_ns(node)->ops->type != ns_type);
+	VFS_WARN_ON_ONCE(node_to_ns(node)->ns_type != ns_type);
 
 	return node_to_ns(node);
 }
@@ -211,7 +225,7 @@ struct ns_common *__ns_tree_adjoined_rcu(struct ns_common *ns,
 	if (list_is_head(list, &ns_tree->ns_list))
 		return ERR_PTR(-ENOENT);
 
-	VFS_WARN_ON_ONCE(list_entry_rcu(list, struct ns_common, ns_list_node)->ops->type != ns_tree->type);
+	VFS_WARN_ON_ONCE(list_entry_rcu(list, struct ns_common, ns_list_node)->ns_type != ns_tree->type);
 
 	return list_entry_rcu(list, struct ns_common, ns_list_node);
 }
diff --git a/kernel/pid.c b/kernel/pid.c
index 7e8c66e0bf67..0c2dcddb317a 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -85,6 +85,7 @@ struct pid_namespace init_pid_ns = {
 #if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
 	.memfd_noexec_scope = MEMFD_NOEXEC_SCOPE_EXEC,
 #endif
+	.ns.ns_type = ns_common_type(&init_pid_ns),
 };
 EXPORT_SYMBOL_GPL(init_pid_ns);
 
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index a262a3f19443..f5b222c8ac39 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -443,7 +443,6 @@ static struct user_namespace *pidns_owner(struct ns_common *ns)
 
 const struct proc_ns_operations pidns_operations = {
 	.name		= "pid",
-	.type		= CLONE_NEWPID,
 	.get		= pidns_get,
 	.put		= pidns_put,
 	.install	= pidns_install,
@@ -454,7 +453,6 @@ const struct proc_ns_operations pidns_operations = {
 const struct proc_ns_operations pidns_for_children_operations = {
 	.name		= "pid_for_children",
 	.real_ns_name	= "pid",
-	.type		= CLONE_NEWPID,
 	.get		= pidns_for_children_get,
 	.put		= pidns_put,
 	.install	= pidns_install,
diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index 9f26e61be044..530cf99c2212 100644
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -462,7 +462,6 @@ out:
 
 const struct proc_ns_operations timens_operations = {
 	.name		= "time",
-	.type		= CLONE_NEWTIME,
 	.get		= timens_get,
 	.put		= timens_put,
 	.install	= timens_install,
@@ -472,7 +471,6 @@ const struct proc_ns_operations timens_operations = {
 const struct proc_ns_operations timens_for_children_operations = {
 	.name		= "time_for_children",
 	.real_ns_name	= "time",
-	.type		= CLONE_NEWTIME,
 	.get		= timens_for_children_get,
 	.put		= timens_put,
 	.install	= timens_install,
@@ -480,6 +478,7 @@ const struct proc_ns_operations timens_for_children_operations = {
 };
 
 struct time_namespace init_time_ns = {
+	.ns.ns_type	= ns_common_type(&init_time_ns),
 	.ns.__ns_ref	= REFCOUNT_INIT(3),
 	.user_ns	= &init_user_ns,
 	.ns.inum	= ns_init_inum(&init_time_ns),
diff --git a/kernel/user.c b/kernel/user.c
index b2a53674d506..0163665914c9 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -65,6 +65,7 @@ struct user_namespace init_user_ns = {
 			.nr_extents = 1,
 		},
 	},
+	.ns.ns_type = ns_common_type(&init_user_ns),
 	.ns.__ns_ref = REFCOUNT_INIT(3),
 	.owner = GLOBAL_ROOT_UID,
 	.group = GLOBAL_ROOT_GID,
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index e1559e8a8a02..03cb63883d04 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -1400,7 +1400,6 @@ static struct user_namespace *userns_owner(struct ns_common *ns)
 
 const struct proc_ns_operations userns_operations = {
 	.name		= "user",
-	.type		= CLONE_NEWUSER,
 	.get		= userns_get,
 	.put		= userns_put,
 	.install	= userns_install,
diff --git a/kernel/utsname.c b/kernel/utsname.c
index 00001592ad13..a8cdc84648ee 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -146,7 +146,6 @@ static struct user_namespace *utsns_owner(struct ns_common *ns)
 
 const struct proc_ns_operations utsns_operations = {
 	.name		= "uts",
-	.type		= CLONE_NEWUTS,
 	.get		= utsns_get,
 	.put		= utsns_put,
 	.install	= utsns_install,