text: // 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 unsigned 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;
  	unsigned res = POLLIN | POLLRDNORM;
  	int event;
  
  	poll_wait(file, &p->ns->poll, wait);
  
  	event = READ_ONCE(ns->event);
  	if (m->poll_event != event) {
  		m->poll_event = event;
  		res |= POLLERR | POLLPRI;
  	}
  
  	return res;
  }
  
  struct proc_fs_info {
  	int flag;
  	const char *str;
  };
  
  static int show_sb_opts(struct seq_file *m, struct super_block *sb)
  {
  	static const struct proc_fs_info fs_info[] = {
  		{ SB_SYNCHRONOUS, ",sync" },
  		{ SB_DIRSYNC, ",dirsync" },
  		{ SB_MANDLOCK, ",mand" },
  		{ SB_LAZYTIME, ",lazytime" },
  		{ 0, NULL }
  	};
  	const struct proc_fs_info *fs_infop;
  
  	for (fs_infop = fs_info; 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_info mnt_info[] = {
  		{ MNT_NOSUID, ",nosuid" },
  		{ MNT_NODEV, ",nodev" },
  		{ MNT_NOEXEC, ",noexec" },
  		{ MNT_NOATIME, ",noatime" },
  		{ MNT_NODIRATIME, ",nodiratime" },
  		{ MNT_RELATIME, ",relatime" },
  		{ 0, NULL }
  	};
  	const struct proc_fs_info *fs_infop;
  
  	for (fs_infop = mnt_info; 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\n\\");
  }
  
  static void show_type(struct seq_file *m, struct super_block *sb)
  {
  	mangle(m, sb->s_type->name);
  	if (sb->s_subtype && sb->s_subtype[0]) {
  		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\n\\");
  	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\n");
  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\n\\");
  	}
  	seq_putc(m, ' ');
  
  	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
  	err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
  	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, '\n');
  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\n\\");
  	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, '\n');
  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;
  	p->cached_event = ~0ULL;
  
  	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);
  	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		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= mounts_release,
  	.poll		= mounts_poll,
  };
  
  const struct file_operations proc_mountinfo_operations = {
  	.open		= mountinfo_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= mounts_release,
  	.poll		= mounts_poll,
  };
  
  const struct file_operations proc_mountstats_operations = {
  	.open		= mountstats_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= mounts_release,
  };
  