Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1713 insertions, 0 deletions

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
new file mode 100644
index 0000000000..de484195f4
--- /dev/null
+++ b/fs/proc/proc_sysctl.c
@@ -0,0 +1,1713 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * /proc/sys support
+ */
+#include <linux/init.h>
+#include <linux/sysctl.h>
+#include <linux/poll.h>
+#include <linux/proc_fs.h>
+#include <linux/printk.h>
+#include <linux/security.h>
+#include <linux/sched.h>
+#include <linux/cred.h>
+#include <linux/namei.h>
+#include <linux/mm.h>
+#include <linux/uio.h>
+#include <linux/module.h>
+#include <linux/bpf-cgroup.h>
+#include <linux/mount.h>
+#include <linux/kmemleak.h>
+#include "internal.h"
+
+#define list_for_each_table_entry(entry, header)	\
+	entry = header->ctl_table;			\
+	for (size_t i = 0 ; i < header->ctl_table_size && entry->procname; ++i, entry++)
+
+static const struct dentry_operations proc_sys_dentry_operations;
+static const struct file_operations proc_sys_file_operations;
+static const struct inode_operations proc_sys_inode_operations;
+static const struct file_operations proc_sys_dir_file_operations;
+static const struct inode_operations proc_sys_dir_operations;
+
+/* Support for permanently empty directories */
+static struct ctl_table sysctl_mount_point[] = {
+	{.type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY }
+};
+
+/**
+ * register_sysctl_mount_point() - registers a sysctl mount point
+ * @path: path for the mount point
+ *
+ * Used to create a permanently empty directory to serve as mount point.
+ * There are some subtle but important permission checks this allows in the
+ * case of unprivileged mounts.
+ */
+struct ctl_table_header *register_sysctl_mount_point(const char *path)
+{
+	return register_sysctl_sz(path, sysctl_mount_point, 0);
+}
+EXPORT_SYMBOL(register_sysctl_mount_point);
+
+#define sysctl_is_perm_empty_ctl_table(tptr)		\
+	(tptr[0].type == SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)
+#define sysctl_is_perm_empty_ctl_header(hptr)		\
+	(sysctl_is_perm_empty_ctl_table(hptr->ctl_table))
+#define sysctl_set_perm_empty_ctl_header(hptr)		\
+	(hptr->ctl_table[0].type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)
+#define sysctl_clear_perm_empty_ctl_header(hptr)	\
+	(hptr->ctl_table[0].type = SYSCTL_TABLE_TYPE_DEFAULT)
+
+void proc_sys_poll_notify(struct ctl_table_poll *poll)
+{
+	if (!poll)
+		return;
+
+	atomic_inc(&poll->event);
+	wake_up_interruptible(&poll->wait);
+}
+
+static struct ctl_table root_table[] = {
+	{
+		.procname = "",
+		.mode = S_IFDIR|S_IRUGO|S_IXUGO,
+	},
+	{ }
+};
+static struct ctl_table_root sysctl_table_root = {
+	.default_set.dir.header = {
+		{{.count = 1,
+		  .nreg = 1,
+		  .ctl_table = root_table }},
+		.ctl_table_arg = root_table,
+		.root = &sysctl_table_root,
+		.set = &sysctl_table_root.default_set,
+	},
+};
+
+static DEFINE_SPINLOCK(sysctl_lock);
+
+static void drop_sysctl_table(struct ctl_table_header *header);
+static int sysctl_follow_link(struct ctl_table_header **phead,
+	struct ctl_table **pentry);
+static int insert_links(struct ctl_table_header *head);
+static void put_links(struct ctl_table_header *header);
+
+static void sysctl_print_dir(struct ctl_dir *dir)
+{
+	if (dir->header.parent)
+		sysctl_print_dir(dir->header.parent);
+	pr_cont("%s/", dir->header.ctl_table[0].procname);
+}
+
+static int namecmp(const char *name1, int len1, const char *name2, int len2)
+{
+	int cmp;
+
+	cmp = memcmp(name1, name2, min(len1, len2));
+	if (cmp == 0)
+		cmp = len1 - len2;
+	return cmp;
+}
+
+/* Called under sysctl_lock */
+static struct ctl_table *find_entry(struct ctl_table_header **phead,
+	struct ctl_dir *dir, const char *name, int namelen)
+{
+	struct ctl_table_header *head;
+	struct ctl_table *entry;
+	struct rb_node *node = dir->root.rb_node;
+
+	while (node)
+	{
+		struct ctl_node *ctl_node;
+		const char *procname;
+		int cmp;
+
+		ctl_node = rb_entry(node, struct ctl_node, node);
+		head = ctl_node->header;
+		entry = &head->ctl_table[ctl_node - head->node];
+		procname = entry->procname;
+
+		cmp = namecmp(name, namelen, procname, strlen(procname));
+		if (cmp < 0)
+			node = node->rb_left;
+		else if (cmp > 0)
+			node = node->rb_right;
+		else {
+			*phead = head;
+			return entry;
+		}
+	}
+	return NULL;
+}
+
+static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
+{
+	struct rb_node *node = &head->node[entry - head->ctl_table].node;
+	struct rb_node **p = &head->parent->root.rb_node;
+	struct rb_node *parent = NULL;
+	const char *name = entry->procname;
+	int namelen = strlen(name);
+
+	while (*p) {
+		struct ctl_table_header *parent_head;
+		struct ctl_table *parent_entry;
+		struct ctl_node *parent_node;
+		const char *parent_name;
+		int cmp;
+
+		parent = *p;
+		parent_node = rb_entry(parent, struct ctl_node, node);
+		parent_head = parent_node->header;
+		parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
+		parent_name = parent_entry->procname;
+
+		cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
+		if (cmp < 0)
+			p = &(*p)->rb_left;
+		else if (cmp > 0)
+			p = &(*p)->rb_right;
+		else {
+			pr_err("sysctl duplicate entry: ");
+			sysctl_print_dir(head->parent);
+			pr_cont("%s\n", entry->procname);
+			return -EEXIST;
+		}
+	}
+
+	rb_link_node(node, parent, p);
+	rb_insert_color(node, &head->parent->root);
+	return 0;
+}
+
+static void erase_entry(struct ctl_table_header *head, struct ctl_table *entry)
+{
+	struct rb_node *node = &head->node[entry - head->ctl_table].node;
+
+	rb_erase(node, &head->parent->root);
+}
+
+static void init_header(struct ctl_table_header *head,
+	struct ctl_table_root *root, struct ctl_table_set *set,
+	struct ctl_node *node, struct ctl_table *table, size_t table_size)
+{
+	head->ctl_table = table;
+	head->ctl_table_size = table_size;
+	head->ctl_table_arg = table;
+	head->used = 0;
+	head->count = 1;
+	head->nreg = 1;
+	head->unregistering = NULL;
+	head->root = root;
+	head->set = set;
+	head->parent = NULL;
+	head->node = node;
+	INIT_HLIST_HEAD(&head->inodes);
+	if (node) {
+		struct ctl_table *entry;
+
+		list_for_each_table_entry(entry, head) {
+			node->header = head;
+			node++;
+		}
+	}
+}
+
+static void erase_header(struct ctl_table_header *head)
+{
+	struct ctl_table *entry;
+
+	list_for_each_table_entry(entry, head)
+		erase_entry(head, entry);
+}
+
+static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
+{
+	struct ctl_table *entry;
+	struct ctl_table_header *dir_h = &dir->header;
+	int err;
+
+
+	/* Is this a permanently empty directory? */
+	if (sysctl_is_perm_empty_ctl_header(dir_h))
+		return -EROFS;
+
+	/* Am I creating a permanently empty directory? */
+	if (sysctl_is_perm_empty_ctl_table(header->ctl_table)) {
+		if (!RB_EMPTY_ROOT(&dir->root))
+			return -EINVAL;
+		sysctl_set_perm_empty_ctl_header(dir_h);
+	}
+
+	dir_h->nreg++;
+	header->parent = dir;
+	err = insert_links(header);
+	if (err)
+		goto fail_links;
+	list_for_each_table_entry(entry, header) {
+		err = insert_entry(header, entry);
+		if (err)
+			goto fail;
+	}
+	return 0;
+fail:
+	erase_header(header);
+	put_links(header);
+fail_links:
+	if (header->ctl_table == sysctl_mount_point)
+		sysctl_clear_perm_empty_ctl_header(dir_h);
+	header->parent = NULL;
+	drop_sysctl_table(dir_h);
+	return err;
+}
+
+/* called under sysctl_lock */
+static int use_table(struct ctl_table_header *p)
+{
+	if (unlikely(p->unregistering))
+		return 0;
+	p->used++;
+	return 1;
+}
+
+/* called under sysctl_lock */
+static void unuse_table(struct ctl_table_header *p)
+{
+	if (!--p->used)
+		if (unlikely(p->unregistering))
+			complete(p->unregistering);
+}
+
+static void proc_sys_invalidate_dcache(struct ctl_table_header *head)
+{
+	proc_invalidate_siblings_dcache(&head->inodes, &sysctl_lock);
+}
+
+/* called under sysctl_lock, will reacquire if has to wait */
+static void start_unregistering(struct ctl_table_header *p)
+{
+	/*
+	 * if p->used is 0, nobody will ever touch that entry again;
+	 * we'll eliminate all paths to it before dropping sysctl_lock
+	 */
+	if (unlikely(p->used)) {
+		struct completion wait;
+		init_completion(&wait);
+		p->unregistering = &wait;
+		spin_unlock(&sysctl_lock);
+		wait_for_completion(&wait);
+	} else {
+		/* anything non-NULL; we'll never dereference it */
+		p->unregistering = ERR_PTR(-EINVAL);
+		spin_unlock(&sysctl_lock);
+	}
+	/*
+	 * Invalidate dentries for unregistered sysctls: namespaced sysctls
+	 * can have duplicate names and contaminate dcache very badly.
+	 */
+	proc_sys_invalidate_dcache(p);
+	/*
+	 * do not remove from the list until nobody holds it; walking the
+	 * list in do_sysctl() relies on that.
+	 */
+	spin_lock(&sysctl_lock);
+	erase_header(p);
+}
+
+static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
+{
+	BUG_ON(!head);
+	spin_lock(&sysctl_lock);
+	if (!use_table(head))
+		head = ERR_PTR(-ENOENT);
+	spin_unlock(&sysctl_lock);
+	return head;
+}
+
+static void sysctl_head_finish(struct ctl_table_header *head)
+{
+	if (!head)
+		return;
+	spin_lock(&sysctl_lock);
+	unuse_table(head);
+	spin_unlock(&sysctl_lock);
+}
+
+static struct ctl_table_set *
+lookup_header_set(struct ctl_table_root *root)
+{
+	struct ctl_table_set *set = &root->default_set;
+	if (root->lookup)
+		set = root->lookup(root);
+	return set;
+}
+
+static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
+				      struct ctl_dir *dir,
+				      const char *name, int namelen)
+{
+	struct ctl_table_header *head;
+	struct ctl_table *entry;
+
+	spin_lock(&sysctl_lock);
+	entry = find_entry(&head, dir, name, namelen);
+	if (entry && use_table(head))
+		*phead = head;
+	else
+		entry = NULL;
+	spin_unlock(&sysctl_lock);
+	return entry;
+}
+
+static struct ctl_node *first_usable_entry(struct rb_node *node)
+{
+	struct ctl_node *ctl_node;
+
+	for (;node; node = rb_next(node)) {
+		ctl_node = rb_entry(node, struct ctl_node, node);
+		if (use_table(ctl_node->header))
+			return ctl_node;
+	}
+	return NULL;
+}
+
+static void first_entry(struct ctl_dir *dir,
+	struct ctl_table_header **phead, struct ctl_table **pentry)
+{
+	struct ctl_table_header *head = NULL;
+	struct ctl_table *entry = NULL;
+	struct ctl_node *ctl_node;
+
+	spin_lock(&sysctl_lock);
+	ctl_node = first_usable_entry(rb_first(&dir->root));
+	spin_unlock(&sysctl_lock);
+	if (ctl_node) {
+		head = ctl_node->header;
+		entry = &head->ctl_table[ctl_node - head->node];
+	}
+	*phead = head;
+	*pentry = entry;
+}
+
+static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentry)
+{
+	struct ctl_table_header *head = *phead;
+	struct ctl_table *entry = *pentry;
+	struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
+
+	spin_lock(&sysctl_lock);
+	unuse_table(head);
+
+	ctl_node = first_usable_entry(rb_next(&ctl_node->node));
+	spin_unlock(&sysctl_lock);
+	head = NULL;
+	if (ctl_node) {
+		head = ctl_node->header;
+		entry = &head->ctl_table[ctl_node - head->node];
+	}
+	*phead = head;
+	*pentry = entry;
+}
+
+/*
+ * sysctl_perm does NOT grant the superuser all rights automatically, because
+ * some sysctl variables are readonly even to root.
+ */
+
+static int test_perm(int mode, int op)
+{
+	if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
+		mode >>= 6;
+	else if (in_egroup_p(GLOBAL_ROOT_GID))
+		mode >>= 3;
+	if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
+		return 0;
+	return -EACCES;
+}
+
+static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, int op)
+{
+	struct ctl_table_root *root = head->root;
+	int mode;
+
+	if (root->permissions)
+		mode = root->permissions(head, table);
+	else
+		mode = table->mode;
+
+	return test_perm(mode, op);
+}
+
+static struct inode *proc_sys_make_inode(struct super_block *sb,
+		struct ctl_table_header *head, struct ctl_table *table)
+{
+	struct ctl_table_root *root = head->root;
+	struct inode *inode;
+	struct proc_inode *ei;
+
+	inode = new_inode(sb);
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+
+	inode->i_ino = get_next_ino();
+
+	ei = PROC_I(inode);
+
+	spin_lock(&sysctl_lock);
+	if (unlikely(head->unregistering)) {
+		spin_unlock(&sysctl_lock);
+		iput(inode);
+		return ERR_PTR(-ENOENT);
+	}
+	ei->sysctl = head;
+	ei->sysctl_entry = table;
+	hlist_add_head_rcu(&ei->sibling_inodes, &head->inodes);
+	head->count++;
+	spin_unlock(&sysctl_lock);
+
+	inode->i_mtime = inode->i_atime = inode_set_ctime_current(inode);
+	inode->i_mode = table->mode;
+	if (!S_ISDIR(table->mode)) {
+		inode->i_mode |= S_IFREG;
+		inode->i_op = &proc_sys_inode_operations;
+		inode->i_fop = &proc_sys_file_operations;
+	} else {
+		inode->i_mode |= S_IFDIR;
+		inode->i_op = &proc_sys_dir_operations;
+		inode->i_fop = &proc_sys_dir_file_operations;
+		if (sysctl_is_perm_empty_ctl_header(head))
+			make_empty_dir_inode(inode);
+	}
+
+	if (root->set_ownership)
+		root->set_ownership(head, table, &inode->i_uid, &inode->i_gid);
+	else {
+		inode->i_uid = GLOBAL_ROOT_UID;
+		inode->i_gid = GLOBAL_ROOT_GID;
+	}
+
+	return inode;
+}
+
+void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
+{
+	spin_lock(&sysctl_lock);
+	hlist_del_init_rcu(&PROC_I(inode)->sibling_inodes);
+	if (!--head->count)
+		kfree_rcu(head, rcu);
+	spin_unlock(&sysctl_lock);
+}
+
+static struct ctl_table_header *grab_header(struct inode *inode)
+{
+	struct ctl_table_header *head = PROC_I(inode)->sysctl;
+	if (!head)
+		head = &sysctl_table_root.default_set.dir.header;
+	return sysctl_head_grab(head);
+}
+
+static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
+					unsigned int flags)
+{
+	struct ctl_table_header *head = grab_header(dir);
+	struct ctl_table_header *h = NULL;
+	const struct qstr *name = &dentry->d_name;
+	struct ctl_table *p;
+	struct inode *inode;
+	struct dentry *err = ERR_PTR(-ENOENT);
+	struct ctl_dir *ctl_dir;
+	int ret;
+
+	if (IS_ERR(head))
+		return ERR_CAST(head);
+
+	ctl_dir = container_of(head, struct ctl_dir, header);
+
+	p = lookup_entry(&h, ctl_dir, name->name, name->len);
+	if (!p)
+		goto out;
+
+	if (S_ISLNK(p->mode)) {
+		ret = sysctl_follow_link(&h, &p);
+		err = ERR_PTR(ret);
+		if (ret)
+			goto out;
+	}
+
+	inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
+	if (IS_ERR(inode)) {
+		err = ERR_CAST(inode);
+		goto out;
+	}
+
+	d_set_d_op(dentry, &proc_sys_dentry_operations);
+	err = d_splice_alias(inode, dentry);
+
+out:
+	if (h)
+		sysctl_head_finish(h);
+	sysctl_head_finish(head);
+	return err;
+}
+
+static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter,
+		int write)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	struct ctl_table_header *head = grab_header(inode);
+	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
+	size_t count = iov_iter_count(iter);
+	char *kbuf;
+	ssize_t error;
+
+	if (IS_ERR(head))
+		return PTR_ERR(head);
+
+	/*
+	 * At this point we know that the sysctl was not unregistered
+	 * and won't be until we finish.
+	 */
+	error = -EPERM;
+	if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))
+		goto out;
+
+	/* if that can happen at all, it should be -EINVAL, not -EISDIR */
+	error = -EINVAL;
+	if (!table->proc_handler)
+		goto out;
+
+	/* don't even try if the size is too large */
+	error = -ENOMEM;
+	if (count >= KMALLOC_MAX_SIZE)
+		goto out;
+	kbuf = kvzalloc(count + 1, GFP_KERNEL);
+	if (!kbuf)
+		goto out;
+
+	if (write) {
+		error = -EFAULT;
+		if (!copy_from_iter_full(kbuf, count, iter))
+			goto out_free_buf;
+		kbuf[count] = '\0';
+	}
+
+	error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count,
+					   &iocb->ki_pos);
+	if (error)
+		goto out_free_buf;
+
+	/* careful: calling conventions are nasty here */
+	error = table->proc_handler(table, write, kbuf, &count, &iocb->ki_pos);
+	if (error)
+		goto out_free_buf;
+
+	if (!write) {
+		error = -EFAULT;
+		if (copy_to_iter(kbuf, count, iter) < count)
+			goto out_free_buf;
+	}
+
+	error = count;
+out_free_buf:
+	kvfree(kbuf);
+out:
+	sysctl_head_finish(head);
+
+	return error;
+}
+
+static ssize_t proc_sys_read(struct kiocb *iocb, struct iov_iter *iter)
+{
+	return proc_sys_call_handler(iocb, iter, 0);
+}
+
+static ssize_t proc_sys_write(struct kiocb *iocb, struct iov_iter *iter)
+{
+	return proc_sys_call_handler(iocb, iter, 1);
+}
+
+static int proc_sys_open(struct inode *inode, struct file *filp)
+{
+	struct ctl_table_header *head = grab_header(inode);
+	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
+
+	/* sysctl was unregistered */
+	if (IS_ERR(head))
+		return PTR_ERR(head);
+
+	if (table->poll)
+		filp->private_data = proc_sys_poll_event(table->poll);
+
+	sysctl_head_finish(head);
+
+	return 0;
+}
+
+static __poll_t proc_sys_poll(struct file *filp, poll_table *wait)
+{
+	struct inode *inode = file_inode(filp);
+	struct ctl_table_header *head = grab_header(inode);
+	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
+	__poll_t ret = DEFAULT_POLLMASK;
+	unsigned long event;
+
+	/* sysctl was unregistered */
+	if (IS_ERR(head))
+		return EPOLLERR | EPOLLHUP;
+
+	if (!table->proc_handler)
+		goto out;
+
+	if (!table->poll)
+		goto out;
+
+	event = (unsigned long)filp->private_data;
+	poll_wait(filp, &table->poll->wait, wait);
+
+	if (event != atomic_read(&table->poll->event)) {
+		filp->private_data = proc_sys_poll_event(table->poll);
+		ret = EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
+	}
+
+out:
+	sysctl_head_finish(head);
+
+	return ret;
+}
+
+static bool proc_sys_fill_cache(struct file *file,
+				struct dir_context *ctx,
+				struct ctl_table_header *head,
+				struct ctl_table *table)
+{
+	struct dentry *child, *dir = file->f_path.dentry;
+	struct inode *inode;
+	struct qstr qname;
+	ino_t ino = 0;
+	unsigned type = DT_UNKNOWN;
+
+	qname.name = table->procname;
+	qname.len  = strlen(table->procname);
+	qname.hash = full_name_hash(dir, qname.name, qname.len);
+
+	child = d_lookup(dir, &qname);
+	if (!child) {
+		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+		child = d_alloc_parallel(dir, &qname, &wq);
+		if (IS_ERR(child))
+			return false;
+		if (d_in_lookup(child)) {
+			struct dentry *res;
+			inode = proc_sys_make_inode(dir->d_sb, head, table);
+			if (IS_ERR(inode)) {
+				d_lookup_done(child);
+				dput(child);
+				return false;
+			}
+			d_set_d_op(child, &proc_sys_dentry_operations);
+			res = d_splice_alias(inode, child);
+			d_lookup_done(child);
+			if (unlikely(res)) {
+				if (IS_ERR(res)) {
+					dput(child);
+					return false;
+				}
+				dput(child);
+				child = res;
+			}
+		}
+	}
+	inode = d_inode(child);
+	ino  = inode->i_ino;
+	type = inode->i_mode >> 12;
+	dput(child);
+	return dir_emit(ctx, qname.name, qname.len, ino, type);
+}
+
+static bool proc_sys_link_fill_cache(struct file *file,
+				    struct dir_context *ctx,
+				    struct ctl_table_header *head,
+				    struct ctl_table *table)
+{
+	bool ret = true;
+
+	head = sysctl_head_grab(head);
+	if (IS_ERR(head))
+		return false;
+
+	/* It is not an error if we can not follow the link ignore it */
+	if (sysctl_follow_link(&head, &table))
+		goto out;
+
+	ret = proc_sys_fill_cache(file, ctx, head, table);
+out:
+	sysctl_head_finish(head);
+	return ret;
+}
+
+static int scan(struct ctl_table_header *head, struct ctl_table *table,
+		unsigned long *pos, struct file *file,
+		struct dir_context *ctx)
+{
+	bool res;
+
+	if ((*pos)++ < ctx->pos)
+		return true;
+
+	if (unlikely(S_ISLNK(table->mode)))
+		res = proc_sys_link_fill_cache(file, ctx, head, table);
+	else
+		res = proc_sys_fill_cache(file, ctx, head, table);
+
+	if (res)
+		ctx->pos = *pos;
+
+	return res;
+}
+
+static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct ctl_table_header *head = grab_header(file_inode(file));
+	struct ctl_table_header *h = NULL;
+	struct ctl_table *entry;
+	struct ctl_dir *ctl_dir;
+	unsigned long pos;
+
+	if (IS_ERR(head))
+		return PTR_ERR(head);
+
+	ctl_dir = container_of(head, struct ctl_dir, header);
+
+	if (!dir_emit_dots(file, ctx))
+		goto out;
+
+	pos = 2;
+
+	for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) {
+		if (!scan(h, entry, &pos, file, ctx)) {
+			sysctl_head_finish(h);
+			break;
+		}
+	}
+out:
+	sysctl_head_finish(head);
+	return 0;
+}
+
+static int proc_sys_permission(struct mnt_idmap *idmap,
+			       struct inode *inode, int mask)
+{
+	/*
+	 * sysctl entries that are not writeable,
+	 * are _NOT_ writeable, capabilities or not.
+	 */
+	struct ctl_table_header *head;
+	struct ctl_table *table;
+	int error;
+
+	/* Executable files are not allowed under /proc/sys/ */
+	if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
+		return -EACCES;
+
+	head = grab_header(inode);
+	if (IS_ERR(head))
+		return PTR_ERR(head);
+
+	table = PROC_I(inode)->sysctl_entry;
+	if (!table) /* global root - r-xr-xr-x */
+		error = mask & MAY_WRITE ? -EACCES : 0;
+	else /* Use the permissions on the sysctl table entry */
+		error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
+
+	sysctl_head_finish(head);
+	return error;
+}
+
+static int proc_sys_setattr(struct mnt_idmap *idmap,
+			    struct dentry *dentry, struct iattr *attr)
+{
+	struct inode *inode = d_inode(dentry);
+	int error;
+
+	if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
+		return -EPERM;
+
+	error = setattr_prepare(&nop_mnt_idmap, dentry, attr);
+	if (error)
+		return error;
+
+	setattr_copy(&nop_mnt_idmap, inode, attr);
+	return 0;
+}
+
+static int proc_sys_getattr(struct mnt_idmap *idmap,
+			    const struct path *path, struct kstat *stat,
+			    u32 request_mask, unsigned int query_flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+	struct ctl_table_header *head = grab_header(inode);
+	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
+
+	if (IS_ERR(head))
+		return PTR_ERR(head);
+
+	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
+	if (table)
+		stat->mode = (stat->mode & S_IFMT) | table->mode;
+
+	sysctl_head_finish(head);
+	return 0;
+}
+
+static const struct file_operations proc_sys_file_operations = {
+	.open		= proc_sys_open,
+	.poll		= proc_sys_poll,
+	.read_iter	= proc_sys_read,
+	.write_iter	= proc_sys_write,
+	.splice_read	= copy_splice_read,
+	.splice_write	= iter_file_splice_write,
+	.llseek		= default_llseek,
+};
+
+static const struct file_operations proc_sys_dir_file_operations = {
+	.read		= generic_read_dir,
+	.iterate_shared	= proc_sys_readdir,
+	.llseek		= generic_file_llseek,
+};
+
+static const struct inode_operations proc_sys_inode_operations = {
+	.permission	= proc_sys_permission,
+	.setattr	= proc_sys_setattr,
+	.getattr	= proc_sys_getattr,
+};
+
+static const struct inode_operations proc_sys_dir_operations = {
+	.lookup		= proc_sys_lookup,
+	.permission	= proc_sys_permission,
+	.setattr	= proc_sys_setattr,
+	.getattr	= proc_sys_getattr,
+};
+
+static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+	return !PROC_I(d_inode(dentry))->sysctl->unregistering;
+}
+
+static int proc_sys_delete(const struct dentry *dentry)
+{
+	return !!PROC_I(d_inode(dentry))->sysctl->unregistering;
+}
+
+static int sysctl_is_seen(struct ctl_table_header *p)
+{
+	struct ctl_table_set *set = p->set;
+	int res;
+	spin_lock(&sysctl_lock);
+	if (p->unregistering)
+		res = 0;
+	else if (!set->is_seen)
+		res = 1;
+	else
+		res = set->is_seen(set);
+	spin_unlock(&sysctl_lock);
+	return res;
+}
+
+static int proc_sys_compare(const struct dentry *dentry,
+		unsigned int len, const char *str, const struct qstr *name)
+{
+	struct ctl_table_header *head;
+	struct inode *inode;
+
+	/* Although proc doesn't have negative dentries, rcu-walk means
+	 * that inode here can be NULL */
+	/* AV: can it, indeed? */
+	inode = d_inode_rcu(dentry);
+	if (!inode)
+		return 1;
+	if (name->len != len)
+		return 1;
+	if (memcmp(name->name, str, len))
+		return 1;
+	head = rcu_dereference(PROC_I(inode)->sysctl);
+	return !head || !sysctl_is_seen(head);
+}
+
+static const struct dentry_operations proc_sys_dentry_operations = {
+	.d_revalidate	= proc_sys_revalidate,
+	.d_delete	= proc_sys_delete,
+	.d_compare	= proc_sys_compare,
+};
+
+static struct ctl_dir *find_subdir(struct ctl_dir *dir,
+				   const char *name, int namelen)
+{
+	struct ctl_table_header *head;
+	struct ctl_table *entry;
+
+	entry = find_entry(&head, dir, name, namelen);
+	if (!entry)
+		return ERR_PTR(-ENOENT);
+	if (!S_ISDIR(entry->mode))
+		return ERR_PTR(-ENOTDIR);
+	return container_of(head, struct ctl_dir, header);
+}
+
+static struct ctl_dir *new_dir(struct ctl_table_set *set,
+			       const char *name, int namelen)
+{
+	struct ctl_table *table;
+	struct ctl_dir *new;
+	struct ctl_node *node;
+	char *new_name;
+
+	new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
+		      sizeof(struct ctl_table)*2 +  namelen + 1,
+		      GFP_KERNEL);
+	if (!new)
+		return NULL;
+
+	node = (struct ctl_node *)(new + 1);
+	table = (struct ctl_table *)(node + 1);
+	new_name = (char *)(table + 2);
+	memcpy(new_name, name, namelen);
+	table[0].procname = new_name;
+	table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
+	init_header(&new->header, set->dir.header.root, set, node, table, 1);
+
+	return new;
+}
+
+/**
+ * get_subdir - find or create a subdir with the specified name.
+ * @dir:  Directory to create the subdirectory in
+ * @name: The name of the subdirectory to find or create
+ * @namelen: The length of name
+ *
+ * Takes a directory with an elevated reference count so we know that
+ * if we drop the lock the directory will not go away.  Upon success
+ * the reference is moved from @dir to the returned subdirectory.
+ * Upon error an error code is returned and the reference on @dir is
+ * simply dropped.
+ */
+static struct ctl_dir *get_subdir(struct ctl_dir *dir,
+				  const char *name, int namelen)
+{
+	struct ctl_table_set *set = dir->header.set;
+	struct ctl_dir *subdir, *new = NULL;
+	int err;
+
+	spin_lock(&sysctl_lock);
+	subdir = find_subdir(dir, name, namelen);
+	if (!IS_ERR(subdir))
+		goto found;
+	if (PTR_ERR(subdir) != -ENOENT)
+		goto failed;
+
+	spin_unlock(&sysctl_lock);
+	new = new_dir(set, name, namelen);
+	spin_lock(&sysctl_lock);
+	subdir = ERR_PTR(-ENOMEM);
+	if (!new)
+		goto failed;
+
+	/* Was the subdir added while we dropped the lock? */
+	subdir = find_subdir(dir, name, namelen);
+	if (!IS_ERR(subdir))
+		goto found;
+	if (PTR_ERR(subdir) != -ENOENT)
+		goto failed;
+
+	/* Nope.  Use the our freshly made directory entry. */
+	err = insert_header(dir, &new->header);
+	subdir = ERR_PTR(err);
+	if (err)
+		goto failed;
+	subdir = new;
+found:
+	subdir->header.nreg++;
+failed:
+	if (IS_ERR(subdir)) {
+		pr_err("sysctl could not get directory: ");
+		sysctl_print_dir(dir);
+		pr_cont("%*.*s %ld\n", namelen, namelen, name,
+			PTR_ERR(subdir));
+	}
+	drop_sysctl_table(&dir->header);
+	if (new)
+		drop_sysctl_table(&new->header);
+	spin_unlock(&sysctl_lock);
+	return subdir;
+}
+
+static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
+{
+	struct ctl_dir *parent;
+	const char *procname;
+	if (!dir->header.parent)
+		return &set->dir;
+	parent = xlate_dir(set, dir->header.parent);
+	if (IS_ERR(parent))
+		return parent;
+	procname = dir->header.ctl_table[0].procname;
+	return find_subdir(parent, procname, strlen(procname));
+}
+
+static int sysctl_follow_link(struct ctl_table_header **phead,
+	struct ctl_table **pentry)
+{
+	struct ctl_table_header *head;
+	struct ctl_table_root *root;
+	struct ctl_table_set *set;
+	struct ctl_table *entry;
+	struct ctl_dir *dir;
+	int ret;
+
+	spin_lock(&sysctl_lock);
+	root = (*pentry)->data;
+	set = lookup_header_set(root);
+	dir = xlate_dir(set, (*phead)->parent);
+	if (IS_ERR(dir))
+		ret = PTR_ERR(dir);
+	else {
+		const char *procname = (*pentry)->procname;
+		head = NULL;
+		entry = find_entry(&head, dir, procname, strlen(procname));
+		ret = -ENOENT;
+		if (entry && use_table(head)) {
+			unuse_table(*phead);
+			*phead = head;
+			*pentry = entry;
+			ret = 0;
+		}
+	}
+
+	spin_unlock(&sysctl_lock);
+	return ret;
+}
+
+static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	pr_err("sysctl table check failed: %s/%s %pV\n",
+	       path, table->procname, &vaf);
+
+	va_end(args);
+	return -EINVAL;
+}
+
+static int sysctl_check_table_array(const char *path, struct ctl_table *table)
+{
+	int err = 0;
+
+	if ((table->proc_handler == proc_douintvec) ||
+	    (table->proc_handler == proc_douintvec_minmax)) {
+		if (table->maxlen != sizeof(unsigned int))
+			err |= sysctl_err(path, table, "array not allowed");
+	}
+
+	if (table->proc_handler == proc_dou8vec_minmax) {
+		if (table->maxlen != sizeof(u8))
+			err |= sysctl_err(path, table, "array not allowed");
+	}
+
+	if (table->proc_handler == proc_dobool) {
+		if (table->maxlen != sizeof(bool))
+			err |= sysctl_err(path, table, "array not allowed");
+	}
+
+	return err;
+}
+
+static int sysctl_check_table(const char *path, struct ctl_table_header *header)
+{
+	struct ctl_table *entry;
+	int err = 0;
+	list_for_each_table_entry(entry, header) {
+		if ((entry->proc_handler == proc_dostring) ||
+		    (entry->proc_handler == proc_dobool) ||
+		    (entry->proc_handler == proc_dointvec) ||
+		    (entry->proc_handler == proc_douintvec) ||
+		    (entry->proc_handler == proc_douintvec_minmax) ||
+		    (entry->proc_handler == proc_dointvec_minmax) ||
+		    (entry->proc_handler == proc_dou8vec_minmax) ||
+		    (entry->proc_handler == proc_dointvec_jiffies) ||
+		    (entry->proc_handler == proc_dointvec_userhz_jiffies) ||
+		    (entry->proc_handler == proc_dointvec_ms_jiffies) ||
+		    (entry->proc_handler == proc_doulongvec_minmax) ||
+		    (entry->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
+			if (!entry->data)
+				err |= sysctl_err(path, entry, "No data");
+			if (!entry->maxlen)
+				err |= sysctl_err(path, entry, "No maxlen");
+			else
+				err |= sysctl_check_table_array(path, entry);
+		}
+		if (!entry->proc_handler)
+			err |= sysctl_err(path, entry, "No proc_handler");
+
+		if ((entry->mode & (S_IRUGO|S_IWUGO)) != entry->mode)
+			err |= sysctl_err(path, entry, "bogus .mode 0%o",
+				entry->mode);
+	}
+	return err;
+}
+
+static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table_header *head)
+{
+	struct ctl_table *link_table, *entry, *link;
+	struct ctl_table_header *links;
+	struct ctl_node *node;
+	char *link_name;
+	int nr_entries, name_bytes;
+
+	name_bytes = 0;
+	nr_entries = 0;
+	list_for_each_table_entry(entry, head) {
+		nr_entries++;
+		name_bytes += strlen(entry->procname) + 1;
+	}
+
+	links = kzalloc(sizeof(struct ctl_table_header) +
+			sizeof(struct ctl_node)*nr_entries +
+			sizeof(struct ctl_table)*(nr_entries + 1) +
+			name_bytes,
+			GFP_KERNEL);
+
+	if (!links)
+		return NULL;
+
+	node = (struct ctl_node *)(links + 1);
+	link_table = (struct ctl_table *)(node + nr_entries);
+	link_name = (char *)&link_table[nr_entries + 1];
+	link = link_table;
+
+	list_for_each_table_entry(entry, head) {
+		int len = strlen(entry->procname) + 1;
+		memcpy(link_name, entry->procname, len);
+		link->procname = link_name;
+		link->mode = S_IFLNK|S_IRWXUGO;
+		link->data = head->root;
+		link_name += len;
+		link++;
+	}
+	init_header(links, dir->header.root, dir->header.set, node, link_table,
+		    head->ctl_table_size);
+	links->nreg = nr_entries;
+
+	return links;
+}
+
+static bool get_links(struct ctl_dir *dir,
+		      struct ctl_table_header *header,
+		      struct ctl_table_root *link_root)
+{
+	struct ctl_table_header *tmp_head;
+	struct ctl_table *entry, *link;
+
+	/* Are there links available for every entry in table? */
+	list_for_each_table_entry(entry, header) {
+		const char *procname = entry->procname;
+		link = find_entry(&tmp_head, dir, procname, strlen(procname));
+		if (!link)
+			return false;
+		if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
+			continue;
+		if (S_ISLNK(link->mode) && (link->data == link_root))
+			continue;
+		return false;
+	}
+
+	/* The checks passed.  Increase the registration count on the links */
+	list_for_each_table_entry(entry, header) {
+		const char *procname = entry->procname;
+		link = find_entry(&tmp_head, dir, procname, strlen(procname));
+		tmp_head->nreg++;
+	}
+	return true;
+}
+
+static int insert_links(struct ctl_table_header *head)
+{
+	struct ctl_table_set *root_set = &sysctl_table_root.default_set;
+	struct ctl_dir *core_parent;
+	struct ctl_table_header *links;
+	int err;
+
+	if (head->set == root_set)
+		return 0;
+
+	core_parent = xlate_dir(root_set, head->parent);
+	if (IS_ERR(core_parent))
+		return 0;
+
+	if (get_links(core_parent, head, head->root))
+		return 0;
+
+	core_parent->header.nreg++;
+	spin_unlock(&sysctl_lock);
+
+	links = new_links(core_parent, head);
+
+	spin_lock(&sysctl_lock);
+	err = -ENOMEM;
+	if (!links)
+		goto out;
+
+	err = 0;
+	if (get_links(core_parent, head, head->root)) {
+		kfree(links);
+		goto out;
+	}
+
+	err = insert_header(core_parent, links);
+	if (err)
+		kfree(links);
+out:
+	drop_sysctl_table(&core_parent->header);
+	return err;
+}
+
+/* Find the directory for the ctl_table. If one is not found create it. */
+static struct ctl_dir *sysctl_mkdir_p(struct ctl_dir *dir, const char *path)
+{
+	const char *name, *nextname;
+
+	for (name = path; name; name = nextname) {
+		int namelen;
+		nextname = strchr(name, '/');
+		if (nextname) {
+			namelen = nextname - name;
+			nextname++;
+		} else {
+			namelen = strlen(name);
+		}
+		if (namelen == 0)
+			continue;
+
+		/*
+		 * namelen ensures if name is "foo/bar/yay" only foo is
+		 * registered first. We traverse as if using mkdir -p and
+		 * return a ctl_dir for the last directory entry.
+		 */
+		dir = get_subdir(dir, name, namelen);
+		if (IS_ERR(dir))
+			break;
+	}
+	return dir;
+}
+
+/**
+ * __register_sysctl_table - register a leaf sysctl table
+ * @set: Sysctl tree to register on
+ * @path: The path to the directory the sysctl table is in.
+ * @table: the top-level table structure without any child. This table
+ * 	 should not be free'd after registration. So it should not be
+ * 	 used on stack. It can either be a global or dynamically allocated
+ * 	 by the caller and free'd later after sysctl unregistration.
+ * @table_size : The number of elements in table
+ *
+ * Register a sysctl table hierarchy. @table should be a filled in ctl_table
+ * array. A completely 0 filled entry terminates the table.
+ *
+ * The members of the &struct ctl_table structure are used as follows:
+ *
+ * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
+ *            enter a sysctl file
+ *
+ * data - a pointer to data for use by proc_handler
+ *
+ * maxlen - the maximum size in bytes of the data
+ *
+ * mode - the file permissions for the /proc/sys file
+ *
+ * child - must be %NULL.
+ *
+ * proc_handler - the text handler routine (described below)
+ *
+ * extra1, extra2 - extra pointers usable by the proc handler routines
+ * XXX: we should eventually modify these to use long min / max [0]
+ * [0] https://lkml.kernel.org/87zgpte9o4.fsf@email.froward.int.ebiederm.org
+ *
+ * Leaf nodes in the sysctl tree will be represented by a single file
+ * under /proc; non-leaf nodes (where child is not NULL) are not allowed,
+ * sysctl_check_table() verifies this.
+ *
+ * There must be a proc_handler routine for any terminal nodes.
+ * Several default handlers are available to cover common cases -
+ *
+ * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
+ * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
+ * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
+ *
+ * It is the handler's job to read the input buffer from user memory
+ * and process it. The handler should return 0 on success.
+ *
+ * This routine returns %NULL on a failure to register, and a pointer
+ * to the table header on success.
+ */
+struct ctl_table_header *__register_sysctl_table(
+	struct ctl_table_set *set,
+	const char *path, struct ctl_table *table, size_t table_size)
+{
+	struct ctl_table_root *root = set->dir.header.root;
+	struct ctl_table_header *header;
+	struct ctl_dir *dir;
+	struct ctl_node *node;
+
+	header = kzalloc(sizeof(struct ctl_table_header) +
+			 sizeof(struct ctl_node)*table_size, GFP_KERNEL_ACCOUNT);
+	if (!header)
+		return NULL;
+
+	node = (struct ctl_node *)(header + 1);
+	init_header(header, root, set, node, table, table_size);
+	if (sysctl_check_table(path, header))
+		goto fail;
+
+	spin_lock(&sysctl_lock);
+	dir = &set->dir;
+	/* Reference moved down the directory tree get_subdir */
+	dir->header.nreg++;
+	spin_unlock(&sysctl_lock);
+
+	dir = sysctl_mkdir_p(dir, path);
+	if (IS_ERR(dir))
+		goto fail;
+	spin_lock(&sysctl_lock);
+	if (insert_header(dir, header))
+		goto fail_put_dir_locked;
+
+	drop_sysctl_table(&dir->header);
+	spin_unlock(&sysctl_lock);
+
+	return header;
+
+fail_put_dir_locked:
+	drop_sysctl_table(&dir->header);
+	spin_unlock(&sysctl_lock);
+fail:
+	kfree(header);
+	return NULL;
+}
+
+/**
+ * register_sysctl_sz - register a sysctl table
+ * @path: The path to the directory the sysctl table is in. If the path
+ * 	doesn't exist we will create it for you.
+ * @table: the table structure. The calller must ensure the life of the @table
+ * 	will be kept during the lifetime use of the syctl. It must not be freed
+ * 	until unregister_sysctl_table() is called with the given returned table
+ * 	with this registration. If your code is non modular then you don't need
+ * 	to call unregister_sysctl_table() and can instead use something like
+ * 	register_sysctl_init() which does not care for the result of the syctl
+ * 	registration.
+ * @table_size: The number of elements in table.
+ *
+ * Register a sysctl table. @table should be a filled in ctl_table
+ * array. A completely 0 filled entry terminates the table.
+ *
+ * See __register_sysctl_table for more details.
+ */
+struct ctl_table_header *register_sysctl_sz(const char *path, struct ctl_table *table,
+					    size_t table_size)
+{
+	return __register_sysctl_table(&sysctl_table_root.default_set,
+					path, table, table_size);
+}
+EXPORT_SYMBOL(register_sysctl_sz);
+
+/**
+ * __register_sysctl_init() - register sysctl table to path
+ * @path: path name for sysctl base. If that path doesn't exist we will create
+ * 	it for you.
+ * @table: This is the sysctl table that needs to be registered to the path.
+ * 	The caller must ensure the life of the @table will be kept during the
+ * 	lifetime use of the sysctl.
+ * @table_name: The name of sysctl table, only used for log printing when
+ *              registration fails
+ * @table_size: The number of elements in table
+ *
+ * The sysctl interface is used by userspace to query or modify at runtime
+ * a predefined value set on a variable. These variables however have default
+ * values pre-set. Code which depends on these variables will always work even
+ * if register_sysctl() fails. If register_sysctl() fails you'd just loose the
+ * ability to query or modify the sysctls dynamically at run time. Chances of
+ * register_sysctl() failing on init are extremely low, and so for both reasons
+ * this function does not return any error as it is used by initialization code.
+ *
+ * Context: if your base directory does not exist it will be created for you.
+ */
+void __init __register_sysctl_init(const char *path, struct ctl_table *table,
+				 const char *table_name, size_t table_size)
+{
+	struct ctl_table_header *hdr = register_sysctl_sz(path, table, table_size);
+
+	if (unlikely(!hdr)) {
+		pr_err("failed when register_sysctl_sz %s to %s\n", table_name, path);
+		return;
+	}
+	kmemleak_not_leak(hdr);
+}
+
+static void put_links(struct ctl_table_header *header)
+{
+	struct ctl_table_set *root_set = &sysctl_table_root.default_set;
+	struct ctl_table_root *root = header->root;
+	struct ctl_dir *parent = header->parent;
+	struct ctl_dir *core_parent;
+	struct ctl_table *entry;
+
+	if (header->set == root_set)
+		return;
+
+	core_parent = xlate_dir(root_set, parent);
+	if (IS_ERR(core_parent))
+		return;
+
+	list_for_each_table_entry(entry, header) {
+		struct ctl_table_header *link_head;
+		struct ctl_table *link;
+		const char *name = entry->procname;
+
+		link = find_entry(&link_head, core_parent, name, strlen(name));
+		if (link &&
+		    ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
+		     (S_ISLNK(link->mode) && (link->data == root)))) {
+			drop_sysctl_table(link_head);
+		}
+		else {
+			pr_err("sysctl link missing during unregister: ");
+			sysctl_print_dir(parent);
+			pr_cont("%s\n", name);
+		}
+	}
+}
+
+static void drop_sysctl_table(struct ctl_table_header *header)
+{
+	struct ctl_dir *parent = header->parent;
+
+	if (--header->nreg)
+		return;
+
+	if (parent) {
+		put_links(header);
+		start_unregistering(header);
+	}
+
+	if (!--header->count)
+		kfree_rcu(header, rcu);
+
+	if (parent)
+		drop_sysctl_table(&parent->header);
+}
+
+/**
+ * unregister_sysctl_table - unregister a sysctl table hierarchy
+ * @header: the header returned from register_sysctl or __register_sysctl_table
+ *
+ * Unregisters the sysctl table and all children. proc entries may not
+ * actually be removed until they are no longer used by anyone.
+ */
+void unregister_sysctl_table(struct ctl_table_header * header)
+{
+	might_sleep();
+
+	if (header == NULL)
+		return;
+
+	spin_lock(&sysctl_lock);
+	drop_sysctl_table(header);
+	spin_unlock(&sysctl_lock);
+}
+EXPORT_SYMBOL(unregister_sysctl_table);
+
+void setup_sysctl_set(struct ctl_table_set *set,
+	struct ctl_table_root *root,
+	int (*is_seen)(struct ctl_table_set *))
+{
+	memset(set, 0, sizeof(*set));
+	set->is_seen = is_seen;
+	init_header(&set->dir.header, root, set, NULL, root_table, 1);
+}
+
+void retire_sysctl_set(struct ctl_table_set *set)
+{
+	WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
+}
+
+int __init proc_sys_init(void)
+{
+	struct proc_dir_entry *proc_sys_root;
+
+	proc_sys_root = proc_mkdir("sys", NULL);
+	proc_sys_root->proc_iops = &proc_sys_dir_operations;
+	proc_sys_root->proc_dir_ops = &proc_sys_dir_file_operations;
+	proc_sys_root->nlink = 0;
+
+	return sysctl_init_bases();
+}
+
+struct sysctl_alias {
+	const char *kernel_param;
+	const char *sysctl_param;
+};
+
+/*
+ * Historically some settings had both sysctl and a command line parameter.
+ * With the generic sysctl. parameter support, we can handle them at a single
+ * place and only keep the historical name for compatibility. This is not meant
+ * to add brand new aliases. When adding existing aliases, consider whether
+ * the possibly different moment of changing the value (e.g. from early_param
+ * to the moment do_sysctl_args() is called) is an issue for the specific
+ * parameter.
+ */
+static const struct sysctl_alias sysctl_aliases[] = {
+	{"hardlockup_all_cpu_backtrace",	"kernel.hardlockup_all_cpu_backtrace" },
+	{"hung_task_panic",			"kernel.hung_task_panic" },
+	{"numa_zonelist_order",			"vm.numa_zonelist_order" },
+	{"softlockup_all_cpu_backtrace",	"kernel.softlockup_all_cpu_backtrace" },
+	{ }
+};
+
+static const char *sysctl_find_alias(char *param)
+{
+	const struct sysctl_alias *alias;
+
+	for (alias = &sysctl_aliases[0]; alias->kernel_param != NULL; alias++) {
+		if (strcmp(alias->kernel_param, param) == 0)
+			return alias->sysctl_param;
+	}
+
+	return NULL;
+}
+
+bool sysctl_is_alias(char *param)
+{
+	const char *alias = sysctl_find_alias(param);
+
+	return alias != NULL;
+}
+
+/* Set sysctl value passed on kernel command line. */
+static int process_sysctl_arg(char *param, char *val,
+			       const char *unused, void *arg)
+{
+	char *path;
+	struct vfsmount **proc_mnt = arg;
+	struct file_system_type *proc_fs_type;
+	struct file *file;
+	int len;
+	int err;
+	loff_t pos = 0;
+	ssize_t wret;
+
+	if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
+		param += sizeof("sysctl") - 1;
+
+		if (param[0] != '/' && param[0] != '.')
+			return 0;
+
+		param++;
+	} else {
+		param = (char *) sysctl_find_alias(param);
+		if (!param)
+			return 0;
+	}
+
+	if (!val)
+		return -EINVAL;
+	len = strlen(val);
+	if (len == 0)
+		return -EINVAL;
+
+	/*
+	 * To set sysctl options, we use a temporary mount of proc, look up the
+	 * respective sys/ file and write to it. To avoid mounting it when no
+	 * options were given, we mount it only when the first sysctl option is
+	 * found. Why not a persistent mount? There are problems with a
+	 * persistent mount of proc in that it forces userspace not to use any
+	 * proc mount options.
+	 */
+	if (!*proc_mnt) {
+		proc_fs_type = get_fs_type("proc");
+		if (!proc_fs_type) {
+			pr_err("Failed to find procfs to set sysctl from command line\n");
+			return 0;
+		}
+		*proc_mnt = kern_mount(proc_fs_type);
+		put_filesystem(proc_fs_type);
+		if (IS_ERR(*proc_mnt)) {
+			pr_err("Failed to mount procfs to set sysctl from command line\n");
+			return 0;
+		}
+	}
+
+	path = kasprintf(GFP_KERNEL, "sys/%s", param);
+	if (!path)
+		panic("%s: Failed to allocate path for %s\n", __func__, param);
+	strreplace(path, '.', '/');
+
+	file = file_open_root_mnt(*proc_mnt, path, O_WRONLY, 0);
+	if (IS_ERR(file)) {
+		err = PTR_ERR(file);
+		if (err == -ENOENT)
+			pr_err("Failed to set sysctl parameter '%s=%s': parameter not found\n",
+				param, val);
+		else if (err == -EACCES)
+			pr_err("Failed to set sysctl parameter '%s=%s': permission denied (read-only?)\n",
+				param, val);
+		else
+			pr_err("Error %pe opening proc file to set sysctl parameter '%s=%s'\n",
+				file, param, val);
+		goto out;
+	}
+	wret = kernel_write(file, val, len, &pos);
+	if (wret < 0) {
+		err = wret;
+		if (err == -EINVAL)
+			pr_err("Failed to set sysctl parameter '%s=%s': invalid value\n",
+				param, val);
+		else
+			pr_err("Error %pe writing to proc file to set sysctl parameter '%s=%s'\n",
+				ERR_PTR(err), param, val);
+	} else if (wret != len) {
+		pr_err("Wrote only %zd bytes of %d writing to proc file %s to set sysctl parameter '%s=%s\n",
+			wret, len, path, param, val);
+	}
+
+	err = filp_close(file, NULL);
+	if (err)
+		pr_err("Error %pe closing proc file to set sysctl parameter '%s=%s\n",
+			ERR_PTR(err), param, val);
+out:
+	kfree(path);
+	return 0;
+}
+
+void do_sysctl_args(void)
+{
+	char *command_line;
+	struct vfsmount *proc_mnt = NULL;
+
+	command_line = kstrdup(saved_command_line, GFP_KERNEL);
+	if (!command_line)
+		panic("%s: Failed to allocate copy of command line\n", __func__);
+
+	parse_args("Setting sysctl args", command_line,
+		   NULL, 0, -1, -1, &proc_mnt, process_sysctl_arg);
+
+	if (proc_mnt)
+		kern_unmount(proc_mnt);
+
+	kfree(command_line);
+}