v4.19.13 snapshot.
diff --git a/fs/proc/root.c b/fs/proc/root.c
new file mode 100644
index 0000000..f4b1a9d
--- /dev/null
+++ b/fs/proc/root.c
@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/proc/root.c
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ *
+ * proc root directory handling functions
+ */
+
+#include <linux/uaccess.h>
+
+#include <linux/errno.h>
+#include <linux/time.h>
+#include <linux/proc_fs.h>
+#include <linux/stat.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/sched/stat.h>
+#include <linux/module.h>
+#include <linux/bitops.h>
+#include <linux/user_namespace.h>
+#include <linux/mount.h>
+#include <linux/pid_namespace.h>
+#include <linux/parser.h>
+#include <linux/cred.h>
+
+#include "internal.h"
+
+enum {
+ Opt_gid, Opt_hidepid, Opt_err,
+};
+
+static const match_table_t tokens = {
+ {Opt_hidepid, "hidepid=%u"},
+ {Opt_gid, "gid=%u"},
+ {Opt_err, NULL},
+};
+
+int proc_parse_options(char *options, struct pid_namespace *pid)
+{
+ char *p;
+ substring_t args[MAX_OPT_ARGS];
+ int option;
+
+ if (!options)
+ return 1;
+
+ while ((p = strsep(&options, ",")) != NULL) {
+ int token;
+ if (!*p)
+ continue;
+
+ args[0].to = args[0].from = NULL;
+ token = match_token(p, tokens, args);
+ switch (token) {
+ case Opt_gid:
+ if (match_int(&args[0], &option))
+ return 0;
+ pid->pid_gid = make_kgid(current_user_ns(), option);
+ break;
+ case Opt_hidepid:
+ if (match_int(&args[0], &option))
+ return 0;
+ if (option < HIDEPID_OFF ||
+ option > HIDEPID_INVISIBLE) {
+ pr_err("proc: hidepid value must be between 0 and 2.\n");
+ return 0;
+ }
+ pid->hide_pid = option;
+ break;
+ default:
+ pr_err("proc: unrecognized mount option \"%s\" "
+ "or missing value\n", p);
+ return 0;
+ }
+ }
+
+ return 1;
+}
+
+int proc_remount(struct super_block *sb, int *flags, char *data)
+{
+ struct pid_namespace *pid = sb->s_fs_info;
+
+ sync_filesystem(sb);
+ return !proc_parse_options(data, pid);
+}
+
+static struct dentry *proc_mount(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data)
+{
+ struct pid_namespace *ns;
+
+ if (flags & SB_KERNMOUNT) {
+ ns = data;
+ data = NULL;
+ } else {
+ ns = task_active_pid_ns(current);
+ }
+
+ return mount_ns(fs_type, flags, data, ns, ns->user_ns, proc_fill_super);
+}
+
+static void proc_kill_sb(struct super_block *sb)
+{
+ struct pid_namespace *ns;
+
+ ns = (struct pid_namespace *)sb->s_fs_info;
+ if (ns->proc_self)
+ dput(ns->proc_self);
+ if (ns->proc_thread_self)
+ dput(ns->proc_thread_self);
+ kill_anon_super(sb);
+ put_pid_ns(ns);
+}
+
+static struct file_system_type proc_fs_type = {
+ .name = "proc",
+ .mount = proc_mount,
+ .kill_sb = proc_kill_sb,
+ .fs_flags = FS_USERNS_MOUNT,
+};
+
+void __init proc_root_init(void)
+{
+ proc_init_kmemcache();
+ set_proc_pid_nlink();
+ proc_self_init();
+ proc_thread_self_init();
+ proc_symlink("mounts", NULL, "self/mounts");
+
+ proc_net_init();
+ proc_mkdir("fs", NULL);
+ proc_mkdir("driver", NULL);
+ proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
+#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
+ /* just give it a mountpoint */
+ proc_create_mount_point("openprom");
+#endif
+ proc_tty_init();
+ proc_mkdir("bus", NULL);
+ proc_sys_init();
+
+ register_filesystem(&proc_fs_type);
+}
+
+static int proc_root_getattr(const struct path *path, struct kstat *stat,
+ u32 request_mask, unsigned int query_flags)
+{
+ generic_fillattr(d_inode(path->dentry), stat);
+ stat->nlink = proc_root.nlink + nr_processes();
+ return 0;
+}
+
+static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
+{
+ if (!proc_pid_lookup(dir, dentry, flags))
+ return NULL;
+
+ return proc_lookup(dir, dentry, flags);
+}
+
+static int proc_root_readdir(struct file *file, struct dir_context *ctx)
+{
+ if (ctx->pos < FIRST_PROCESS_ENTRY) {
+ int error = proc_readdir(file, ctx);
+ if (unlikely(error <= 0))
+ return error;
+ ctx->pos = FIRST_PROCESS_ENTRY;
+ }
+
+ return proc_pid_readdir(file, ctx);
+}
+
+/*
+ * The root /proc directory is special, as it has the
+ * <pid> directories. Thus we don't use the generic
+ * directory handling functions for that..
+ */
+static const struct file_operations proc_root_operations = {
+ .read = generic_read_dir,
+ .iterate_shared = proc_root_readdir,
+ .llseek = generic_file_llseek,
+};
+
+/*
+ * proc root can do almost nothing..
+ */
+static const struct inode_operations proc_root_inode_operations = {
+ .lookup = proc_root_lookup,
+ .getattr = proc_root_getattr,
+};
+
+/*
+ * This is the root "inode" in the /proc tree..
+ */
+struct proc_dir_entry proc_root = {
+ .low_ino = PROC_ROOT_INO,
+ .namelen = 5,
+ .mode = S_IFDIR | S_IRUGO | S_IXUGO,
+ .nlink = 2,
+ .refcnt = REFCOUNT_INIT(1),
+ .proc_iops = &proc_root_inode_operations,
+ .proc_fops = &proc_root_operations,
+ .parent = &proc_root,
+ .subdir = RB_ROOT,
+ .name = "/proc",
+};
+
+int pid_ns_prepare_proc(struct pid_namespace *ns)
+{
+ struct vfsmount *mnt;
+
+ mnt = kern_mount_data(&proc_fs_type, ns);
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);
+
+ ns->proc_mnt = mnt;
+ return 0;
+}
+
+void pid_ns_release_proc(struct pid_namespace *ns)
+{
+ kern_unmount(ns->proc_mnt);
+}