// 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/fs_context.h>

  #include <linux/mount.h>

  #include <linux/pid_namespace.h>

  #include <linux/fs_parser.h>

  #include <linux/cred.h>

  #include <linux/magic.h>

  #include <linux/slab.h>

  #include "internal.h"

  struct proc_fs_context {
  	struct pid_namespace	*pid_ns;
  	unsigned int		mask;

  	enum proc_hidepid	hidepid;

  	int			gid;

  	enum proc_pidonly	pidonly;

  };

  enum proc_param {
  	Opt_gid,
  	Opt_hidepid,

  	Opt_subset,

  };

  static const struct fs_parameter_spec proc_fs_parameters[] = {

  	fsparam_u32("gid",	Opt_gid),

  	fsparam_string("hidepid",	Opt_hidepid),

  	fsparam_string("subset",	Opt_subset),

  	{}
  };

  static inline int valid_hidepid(unsigned int value)
  {
  	return (value == HIDEPID_OFF ||
  		value == HIDEPID_NO_ACCESS ||
  		value == HIDEPID_INVISIBLE ||
  		value == HIDEPID_NOT_PTRACEABLE);
  }

  static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param)
  {
  	struct proc_fs_context *ctx = fc->fs_private;
  	struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid);
  	struct fs_parse_result result;
  	int base = (unsigned long)hidepid_u32_spec.data;
  
  	if (param->type != fs_value_is_string)
  		return invalf(fc, "proc: unexpected type of hidepid value
  ");
  
  	if (!kstrtouint(param->string, base, &result.uint_32)) {
  		if (!valid_hidepid(result.uint_32))
  			return invalf(fc, "proc: unknown value of hidepid - %s
  ", param->string);
  		ctx->hidepid = result.uint_32;
  		return 0;
  	}
  
  	if (!strcmp(param->string, "off"))
  		ctx->hidepid = HIDEPID_OFF;
  	else if (!strcmp(param->string, "noaccess"))
  		ctx->hidepid = HIDEPID_NO_ACCESS;
  	else if (!strcmp(param->string, "invisible"))
  		ctx->hidepid = HIDEPID_INVISIBLE;
  	else if (!strcmp(param->string, "ptraceable"))
  		ctx->hidepid = HIDEPID_NOT_PTRACEABLE;
  	else
  		return invalf(fc, "proc: unknown value of hidepid - %s
  ", param->string);
  
  	return 0;
  }

  static int proc_parse_subset_param(struct fs_context *fc, char *value)
  {
  	struct proc_fs_context *ctx = fc->fs_private;
  
  	while (value) {
  		char *ptr = strchr(value, ',');
  
  		if (ptr != NULL)
  			*ptr++ = '\0';
  
  		if (*value != '\0') {
  			if (!strcmp(value, "pid")) {
  				ctx->pidonly = PROC_PIDONLY_ON;
  			} else {
  				return invalf(fc, "proc: unsupported subset option - %s
  ", value);
  			}
  		}
  		value = ptr;
  	}
  
  	return 0;
  }

  static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)

  {

  	struct proc_fs_context *ctx = fc->fs_private;
  	struct fs_parse_result result;
  	int opt;

  	opt = fs_parse(fc, proc_fs_parameters, param, &result);

  	if (opt < 0)
  		return opt;
  
  	switch (opt) {
  	case Opt_gid:
  		ctx->gid = result.uint_32;
  		break;
  
  	case Opt_hidepid:

  		if (proc_parse_hidepid_param(fc, param))
  			return -EINVAL;

  		break;

  	case Opt_subset:
  		if (proc_parse_subset_param(fc, param->string) < 0)
  			return -EINVAL;
  		break;

  	default:
  		return -EINVAL;

  	}

  	ctx->mask |= 1 << opt;
  	return 0;

  }

  static void proc_apply_options(struct proc_fs_info *fs_info,

  			       struct fs_context *fc,

  			       struct user_namespace *user_ns)

  {

  	struct proc_fs_context *ctx = fc->fs_private;
  
  	if (ctx->mask & (1 << Opt_gid))

  		fs_info->pid_gid = make_kgid(user_ns, ctx->gid);

  	if (ctx->mask & (1 << Opt_hidepid))

  		fs_info->hide_pid = ctx->hidepid;

  	if (ctx->mask & (1 << Opt_subset))
  		fs_info->pidonly = ctx->pidonly;

  }

  static int proc_fill_super(struct super_block *s, struct fs_context *fc)

  {

  	struct proc_fs_context *ctx = fc->fs_private;

  	struct inode *root_inode;

  	struct proc_fs_info *fs_info;

  	int ret;

  	fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL);
  	if (!fs_info)
  		return -ENOMEM;
  
  	fs_info->pid_ns = get_pid_ns(ctx->pid_ns);
  	proc_apply_options(fs_info, fc, current_user_ns());

  
  	/* User space would break if executables or devices appear on proc */
  	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
  	s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
  	s->s_blocksize = 1024;
  	s->s_blocksize_bits = 10;
  	s->s_magic = PROC_SUPER_MAGIC;
  	s->s_op = &proc_sops;
  	s->s_time_gran = 1;

  	s->s_fs_info = fs_info;

  
  	/*
  	 * procfs isn't actually a stacking filesystem; however, there is
  	 * too much magic going on inside it to permit stacking things on
  	 * top of it
  	 */
  	s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;

  	/* procfs dentries and inodes don't require IO to create */
  	s->s_shrink.seeks = 0;
  
  	pde_get(&proc_root);
  	root_inode = proc_get_inode(s, &proc_root);
  	if (!root_inode) {
  		pr_err("proc_fill_super: get root inode failed
  ");
  		return -ENOMEM;
  	}
  
  	s->s_root = d_make_root(root_inode);
  	if (!s->s_root) {
  		pr_err("proc_fill_super: allocate dentry failed
  ");
  		return -ENOMEM;
  	}
  
  	ret = proc_setup_self(s);
  	if (ret) {
  		return ret;
  	}
  	return proc_setup_thread_self(s);
  }

  static int proc_reconfigure(struct fs_context *fc)

  {

  	struct super_block *sb = fc->root->d_sb;

  	struct proc_fs_info *fs_info = proc_sb_info(sb);

  
  	sync_filesystem(sb);

  	proc_apply_options(fs_info, fc, current_user_ns());

  	return 0;

  }

  static int proc_get_tree(struct fs_context *fc)

  {

  	return get_tree_nodev(fc, proc_fill_super);

  }

  static void proc_fs_context_free(struct fs_context *fc)
  {
  	struct proc_fs_context *ctx = fc->fs_private;

  	put_pid_ns(ctx->pid_ns);

  	kfree(ctx);
  }
  
  static const struct fs_context_operations proc_fs_context_ops = {
  	.free		= proc_fs_context_free,
  	.parse_param	= proc_parse_param,
  	.get_tree	= proc_get_tree,
  	.reconfigure	= proc_reconfigure,
  };
  
  static int proc_init_fs_context(struct fs_context *fc)
  {
  	struct proc_fs_context *ctx;
  
  	ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
  	if (!ctx)
  		return -ENOMEM;

  	ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));

  	put_user_ns(fc->user_ns);
  	fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);

  	fc->fs_private = ctx;
  	fc->ops = &proc_fs_context_ops;
  	return 0;

  }
  
  static void proc_kill_sb(struct super_block *sb)
  {

  	struct proc_fs_info *fs_info = proc_sb_info(sb);

  	if (!fs_info) {
  		kill_anon_super(sb);
  		return;
  	}

  	dput(fs_info->proc_self);
  	dput(fs_info->proc_thread_self);

  	kill_anon_super(sb);
  	put_pid_ns(fs_info->pid_ns);
  	kfree(fs_info);

  }

  static struct file_system_type proc_fs_type = {

  	.name			= "proc",
  	.init_fs_context	= proc_init_fs_context,

  	.parameters		= proc_fs_parameters,

  	.kill_sb		= proc_kill_sb,

  	.fs_flags		= FS_USERNS_MOUNT | FS_DISALLOW_NOTIFY_PERM,

  };

  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(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_dir_ops	= &proc_root_operations,

  	.parent		= &proc_root,

  	.subdir		= RB_ROOT,

  	.name		= "/proc",

  };