// SPDX-License-Identifier: GPL-2.0

  /*
   * fs/proc_namespace.c - handling of /proc/<pid>/{mounts,mountinfo,mountstats}
   *
   * In fact, that's a piece of procfs; it's *almost* isolated from
   * the rest of fs/proc, but has rather close relationships with
   * fs/namespace.c, thus here instead of fs/proc
   *
   */
  #include <linux/mnt_namespace.h>
  #include <linux/nsproxy.h>
  #include <linux/security.h>
  #include <linux/fs_struct.h>

  #include <linux/sched/task.h>

  #include "proc/internal.h" /* only for get_proc_task() in ->open() */
  
  #include "pnode.h"
  #include "internal.h"

  static __poll_t mounts_poll(struct file *file, poll_table *wait)

  {

  	struct seq_file *m = file->private_data;
  	struct proc_mounts *p = m->private;

  	struct mnt_namespace *ns = p->ns;

  	__poll_t res = EPOLLIN | EPOLLRDNORM;

  	int event;

  
  	poll_wait(file, &p->ns->poll, wait);

  	event = READ_ONCE(ns->event);

  	if (m->poll_event != event) {
  		m->poll_event = event;

  		res |= EPOLLERR | EPOLLPRI;

  	}

  
  	return res;
  }

  struct proc_fs_opts {

  	int flag;
  	const char *str;
  };
  
  static int show_sb_opts(struct seq_file *m, struct super_block *sb)
  {

  	static const struct proc_fs_opts fs_opts[] = {

  		{ SB_SYNCHRONOUS, ",sync" },
  		{ SB_DIRSYNC, ",dirsync" },
  		{ SB_MANDLOCK, ",mand" },
  		{ SB_LAZYTIME, ",lazytime" },

  		{ 0, NULL }
  	};

  	const struct proc_fs_opts *fs_infop;

  	for (fs_infop = fs_opts; fs_infop->flag; fs_infop++) {

  		if (sb->s_flags & fs_infop->flag)
  			seq_puts(m, fs_infop->str);
  	}
  
  	return security_sb_show_options(m, sb);
  }
  
  static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
  {

  	static const struct proc_fs_opts mnt_opts[] = {

  		{ MNT_NOSUID, ",nosuid" },
  		{ MNT_NODEV, ",nodev" },
  		{ MNT_NOEXEC, ",noexec" },
  		{ MNT_NOATIME, ",noatime" },
  		{ MNT_NODIRATIME, ",nodiratime" },
  		{ MNT_RELATIME, ",relatime" },

  		{ MNT_NOSYMFOLLOW, ",nosymfollow" },

  		{ 0, NULL }
  	};

  	const struct proc_fs_opts *fs_infop;

  	for (fs_infop = mnt_opts; fs_infop->flag; fs_infop++) {

  		if (mnt->mnt_flags & fs_infop->flag)
  			seq_puts(m, fs_infop->str);
  	}
  }
  
  static inline void mangle(struct seq_file *m, const char *s)
  {
  	seq_escape(m, s, " \t
  \\");
  }
  
  static void show_type(struct seq_file *m, struct super_block *sb)
  {
  	mangle(m, sb->s_type->name);

  	if (sb->s_subtype) {

  		seq_putc(m, '.');
  		mangle(m, sb->s_subtype);
  	}
  }
  
  static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
  {

  	struct proc_mounts *p = m->private;

  	struct mount *r = real_mount(mnt);

  	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };

  	struct super_block *sb = mnt_path.dentry->d_sb;

  	int err;

  	if (sb->s_op->show_devname) {
  		err = sb->s_op->show_devname(m, mnt_path.dentry);

  		if (err)
  			goto out;
  	} else {
  		mangle(m, r->mnt_devname ? r->mnt_devname : "none");
  	}
  	seq_putc(m, ' ');

  	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
  	err = seq_path_root(m, &mnt_path, &p->root, " \t
  \\");
  	if (err)
  		goto out;

  	seq_putc(m, ' ');

  	show_type(m, sb);

  	seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");

  	err = show_sb_opts(m, sb);

  	if (err)
  		goto out;
  	show_mnt_opts(m, mnt);

  	if (sb->s_op->show_options)

  		err = sb->s_op->show_options(m, mnt_path.dentry);

  	seq_puts(m, " 0 0
  ");
  out:
  	return err;
  }
  
  static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
  {

  	struct proc_mounts *p = m->private;

  	struct mount *r = real_mount(mnt);
  	struct super_block *sb = mnt->mnt_sb;
  	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };

  	int err;

  
  	seq_printf(m, "%i %i %u:%u ", r->mnt_id, r->mnt_parent->mnt_id,
  		   MAJOR(sb->s_dev), MINOR(sb->s_dev));

  	if (sb->s_op->show_path) {

  		err = sb->s_op->show_path(m, mnt->mnt_root);

  		if (err)
  			goto out;
  	} else {

  		seq_dentry(m, mnt->mnt_root, " \t
  \\");

  	}

  	seq_putc(m, ' ');
  
  	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */

  	err = seq_path_root(m, &mnt_path, &p->root, " \t
  \\");

  	if (err)
  		goto out;
  
  	seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
  	show_mnt_opts(m, mnt);
  
  	/* Tagged fields ("foo:X" or "bar") */
  	if (IS_MNT_SHARED(r))
  		seq_printf(m, " shared:%i", r->mnt_group_id);
  	if (IS_MNT_SLAVE(r)) {
  		int master = r->mnt_master->mnt_group_id;
  		int dom = get_dominating_id(r, &p->root);
  		seq_printf(m, " master:%i", master);
  		if (dom && dom != master)
  			seq_printf(m, " propagate_from:%i", dom);
  	}
  	if (IS_MNT_UNBINDABLE(r))
  		seq_puts(m, " unbindable");
  
  	/* Filesystem specific data */
  	seq_puts(m, " - ");
  	show_type(m, sb);
  	seq_putc(m, ' ');

  	if (sb->s_op->show_devname) {

  		err = sb->s_op->show_devname(m, mnt->mnt_root);

  		if (err)
  			goto out;
  	} else {

  		mangle(m, r->mnt_devname ? r->mnt_devname : "none");

  	}

  	seq_puts(m, sb_rdonly(sb) ? " ro" : " rw");

  	err = show_sb_opts(m, sb);
  	if (err)
  		goto out;
  	if (sb->s_op->show_options)

  		err = sb->s_op->show_options(m, mnt->mnt_root);

  	seq_putc(m, '
  ');
  out:
  	return err;
  }
  
  static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
  {

  	struct proc_mounts *p = m->private;

  	struct mount *r = real_mount(mnt);
  	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };

  	struct super_block *sb = mnt_path.dentry->d_sb;

  	int err;

  
  	/* device */

  	if (sb->s_op->show_devname) {

  		seq_puts(m, "device ");

  		err = sb->s_op->show_devname(m, mnt_path.dentry);

  		if (err)
  			goto out;

  	} else {
  		if (r->mnt_devname) {
  			seq_puts(m, "device ");
  			mangle(m, r->mnt_devname);
  		} else
  			seq_puts(m, "no device");
  	}
  
  	/* mount point */
  	seq_puts(m, " mounted on ");

  	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
  	err = seq_path_root(m, &mnt_path, &p->root, " \t
  \\");
  	if (err)
  		goto out;

  	seq_putc(m, ' ');
  
  	/* file system type */
  	seq_puts(m, "with fstype ");

  	show_type(m, sb);

  
  	/* optional statistics */

  	if (sb->s_op->show_stats) {

  		seq_putc(m, ' ');

  		err = sb->s_op->show_stats(m, mnt_path.dentry);

  	}
  
  	seq_putc(m, '
  ');

  out:

  	return err;
  }
  
  static int mounts_open_common(struct inode *inode, struct file *file,
  			      int (*show)(struct seq_file *, struct vfsmount *))
  {
  	struct task_struct *task = get_proc_task(inode);
  	struct nsproxy *nsp;
  	struct mnt_namespace *ns = NULL;
  	struct path root;
  	struct proc_mounts *p;

  	struct seq_file *m;

  	int ret = -EINVAL;
  
  	if (!task)
  		goto err;

  	task_lock(task);
  	nsp = task->nsproxy;

  	if (!nsp || !nsp->mnt_ns) {

  		task_unlock(task);

  		put_task_struct(task);
  		goto err;
  	}
  	ns = nsp->mnt_ns;

  	get_mnt_ns(ns);

  	if (!task->fs) {
  		task_unlock(task);
  		put_task_struct(task);
  		ret = -ENOENT;
  		goto err_put_ns;
  	}
  	get_fs_root(task->fs, &root);
  	task_unlock(task);
  	put_task_struct(task);

  	ret = seq_open_private(file, &mounts_op, sizeof(struct proc_mounts));
  	if (ret)

  		goto err_put_path;

  	m = file->private_data;
  	m->poll_event = ns->event;

  	p = m->private;

  	p->ns = ns;
  	p->root = root;

  	p->show = show;

  	INIT_LIST_HEAD(&p->cursor.mnt_list);
  	p->cursor.mnt.mnt_flags = MNT_CURSOR;

  
  	return 0;

   err_put_path:
  	path_put(&root);
   err_put_ns:
  	put_mnt_ns(ns);
   err:
  	return ret;
  }
  
  static int mounts_release(struct inode *inode, struct file *file)
  {

  	struct seq_file *m = file->private_data;
  	struct proc_mounts *p = m->private;

  	path_put(&p->root);

  	mnt_cursor_del(p->ns, &p->cursor);

  	put_mnt_ns(p->ns);

  	return seq_release_private(inode, file);

  }
  
  static int mounts_open(struct inode *inode, struct file *file)
  {
  	return mounts_open_common(inode, file, show_vfsmnt);
  }
  
  static int mountinfo_open(struct inode *inode, struct file *file)
  {
  	return mounts_open_common(inode, file, show_mountinfo);
  }
  
  static int mountstats_open(struct inode *inode, struct file *file)
  {
  	return mounts_open_common(inode, file, show_vfsstat);
  }
  
  const struct file_operations proc_mounts_operations = {
  	.open		= mounts_open,

  	.read_iter	= seq_read_iter,
  	.splice_read	= generic_file_splice_read,

  	.llseek		= seq_lseek,
  	.release	= mounts_release,
  	.poll		= mounts_poll,
  };
  
  const struct file_operations proc_mountinfo_operations = {
  	.open		= mountinfo_open,

  	.read_iter	= seq_read_iter,
  	.splice_read	= generic_file_splice_read,

  	.llseek		= seq_lseek,
  	.release	= mounts_release,
  	.poll		= mounts_poll,
  };
  
  const struct file_operations proc_mountstats_operations = {
  	.open		= mountstats_open,

  	.read_iter	= seq_read_iter,
  	.splice_read	= generic_file_splice_read,

  	.llseek		= seq_lseek,
  	.release	= mounts_release,
  };