path: root/fs/autofs4/dev-ioctl.c

/*
 * Copyright 2008 Red Hat, Inc. All rights reserved.
 * Copyright 2008 Ian Kent <raven@themaw.net>
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 */

#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/miscdevice.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <linux/namei.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/sched.h>
#include <linux/compat.h>
#include <linux/syscalls.h>
#include <linux/smp_lock.h>
#include <linux/magic.h>
#include <linux/dcache.h>
#include <linux/uaccess.h>

#include "autofs_i.h"

/*
 * This module implements an interface for routing autofs ioctl control
 * commands via a miscellaneous device file.
 *
 * The alternate interface is needed because we need to be able open
 * an ioctl file descriptor on an autofs mount that may be covered by
 * another mount. This situation arises when starting automount(8)
 * or other user space daemon which uses direct mounts or offset
 * mounts (used for autofs lazy mount/umount of nested mount trees),
 * which have been left busy at at service shutdown.
 */

#define AUTOFS_DEV_IOCTL_SIZE	sizeof(struct autofs_dev_ioctl)

typedef int (*ioctl_fn)(struct file *, struct autofs_sb_info *,
			struct autofs_dev_ioctl *);

static int check_name(const char *name)
{
	if (!strchr(name, '/'))
		return -EINVAL;
	return 0;
}

/*
 * Check a string doesn't overrun the chunk of
 * memory we copied from user land.
 */
static int invalid_str(char *str, void *end)
{
	while ((void *) str <= end)
		if (!*str++)
			return 0;
	return -EINVAL;
}

/*
 * Check that the user compiled against correct version of autofs
 * misc device code.
 *
 * As well as checking the version compatibility this always copies
 * the kernel interface version out.
 */
static int check_dev_ioctl_version(int cmd, struct autofs_dev_ioctl *param)
{
	int err = 0;

	if ((AUTOFS_DEV_IOCTL_VERSION_MAJOR != param->ver_major) ||
	    (AUTOFS_DEV_IOCTL_VERSION_MINOR < param->ver_minor)) {
		AUTOFS_WARN("ioctl control interface version mismatch: "
		     "kernel(%u.%u), user(%u.%u), cmd(%d)",
		     AUTOFS_DEV_IOCTL_VERSION_MAJOR,
		     AUTOFS_DEV_IOCTL_VERSION_MINOR,
		     param->ver_major, param->ver_minor, cmd);
		err = -EINVAL;
	}

	/* Fill in the kernel version. */
	param->ver_major = AUTOFS_DEV_IOCTL_VERSION_MAJOR;
	param->ver_minor = AUTOFS_DEV_IOCTL_VERSION_MINOR;

	return err;
}

/*
 * Copy parameter control struct, including a possible path allocated
 * at the end of the struct.
 */
static struct autofs_dev_ioctl *copy_dev_ioctl(struct autofs_dev_ioctl __user *in)
{
	struct autofs_dev_ioctl tmp, *ads;

	if (copy_from_user(&tmp, in, sizeof(tmp)))
		return ERR_PTR(-EFAULT);

	if (tmp.size < sizeof(tmp))
		return ERR_PTR(-EINVAL);

	ads = kmalloc(tmp.size, GFP_KERNEL);
	if (!ads)
		return ERR_PTR(-ENOMEM);

	if (copy_from_user(ads, in, tmp.size)) {
		kfree(ads);
		return ERR_PTR(-EFAULT);
	}

	return ads;
}

static inline void free_dev_ioctl(struct autofs_dev_ioctl *param)
{
	kfree(param);
	return;
}

/*
 * Check sanity of parameter control fields and if a path is present
 * check that it has a "/" and is terminated.
 */
static int validate_dev_ioctl(int cmd, struct autofs_dev_ioctl *param)
{
	int err = -EINVAL;

	if (check_dev_ioctl_version(cmd, param)) {
		AUTOFS_WARN("invalid device control module version "
		     "supplied for cmd(0x%08x)", cmd);
		goto out;
	}

	if (param->size > sizeof(*param)) {
		err = check_name(param->path);
		if (err) {
			AUTOFS_WARN("invalid path supplied for cmd(0x%08x)",
				    cmd);
			goto out;
		}

		err = invalid_str(param->path,
				 (void *) ((size_t) param + param->size));
		if (err) {
			AUTOFS_WARN("invalid path supplied for cmd(0x%08x)",
				    cmd);
			goto out;
		}
	}

	err = 0;
out:
	return err;
}

/*
 * Get the autofs super block info struct from the file opened on
 * the autofs mount point.
 */
static struct autofs_sb_info *autofs_dev_ioctl_sbi(struct file *f)
{
	struct autofs_sb_info *sbi = NULL;
	struct inode *inode;

	if (f) {
		inode = f->f_path.dentry->d_inode;
		sbi = autofs4_sbi(inode->i_sb);
	}
	return sbi;
}

/* Return autofs module protocol version */
static int autofs_dev_ioctl_protover(struct file *fp,
				     struct autofs_sb_info *sbi,
				     struct autofs_dev_ioctl *param)
{
	param->arg1 = sbi->version;
	return 0;
}

/* Return autofs module protocol sub version */
static int autofs_dev_ioctl_protosubver(struct file *fp,
					struct autofs_sb_info *sbi,
					struct autofs_dev_ioctl *param)
{
	param->arg1 = sbi->sub_version;
	return 0;
}

/*
 * Walk down the mount stack looking for an autofs mount that
 * has the requested device number (aka. new_encode_dev(sb->s_dev).
 */
static int autofs_dev_ioctl_find_super(struct nameidata *nd, dev_t devno)
{
	struct dentry *dentry;
	struct inode *inode;
	struct super_block *sb;
	dev_t s_dev;
	unsigned int err;

	err = -ENOENT;

	/* Lookup the dentry name at the base of our mount point */
	dentry = d_lookup(nd->path.dentry, &nd->last);
	if (!dentry)
		goto out;

	dput(nd->path.dentry);
	nd->path.dentry = dentry;

	/* And follow the mount stack looking for our autofs mount */
	while (follow_down(&nd->path.mnt, &nd->path.dentry)) {
		inode = nd->path.dentry->d_inode;
		if (!inode)
			break;

		sb = inode->i_sb;
		s_dev = new_encode_dev(sb->s_dev);
		if (devno == s_dev) {
			if (sb->s_magic == AUTOFS_SUPER_MAGIC) {
				err = 0;
				break;
			}
		}
	}
out:
	return err;
}

/*
 * Walk down the mount stack looking for an autofs mount that
 * has the requested mount type (ie. indirect, direct or offset).
 */
static int autofs_dev_ioctl_find_sbi_type(struct nameidata *nd, unsigned int type)
{
	struct dentry *dentry;
	struct autofs_info *ino;
	unsigned int err;

	err = -ENOENT;

	/* Lookup the dentry name at the base of our mount point */
	dentry = d_lookup(nd->path.dentry, &nd->last);
	if (!dentry)
		goto out;

	dput(nd->path.dentry);
	nd->path.dentry = dentry;

	/* And follow the mount stack looking for our autofs mount */
	while (follow_down(&nd->path.mnt, &nd->path.dentry)) {
		ino = autofs4_dentry_ino(nd->path.dentry);
		if (ino && ino->sbi->type & type) {
			err = 0;
			break;
		}
	}
out:
	return err;
}

static void autofs_dev_ioctl_fd_install(unsigned int fd, struct file *file)
{
	struct files_struct *files = current->files;
	struct fdtable *fdt;

	spin_lock(&files->file_lock);
	fdt = files_fdtable(files);
	BUG_ON(fdt->fd[fd] != NULL);
	rcu_assign_pointer(fdt->fd[fd], file);
	FD_SET(fd, fdt->close_on_exec);
	spin_unlock(&files->file_lock);
}


/*
 * Open a file descriptor on the autofs mount point corresponding
 * to the given path and device number (aka. new_encode_dev(sb->s_dev)).
 */
static int autofs_dev_ioctl_open_mountpoint(const char *path, dev_t devid)
{
	struct file *filp;
	struct nameidata nd;
	int err, fd;

	fd = get_unused_fd();
	if (likely(fd >= 0)) {
		/* Get nameidata of the parent directory */
		err = path_lookup(path, LOOKUP_PARENT, &nd);
		if (err)
			goto out;

		/*
		 * Search down, within the parent, looking for an
		 * autofs super block that has the device number
		 * corresponding to the autofs fs we want to open.
		 */
		err = autofs_dev_ioctl_find_super(&nd, devid);
		if (err) {
			path_put(&nd.path);
			goto out;
		}

		filp = dentry_open(nd.path.dentry, nd.path.mnt, O_RDONLY,
				   current_cred());
		if (IS_ERR(filp)) {
			err = PTR_ERR(filp);
			goto out;
		}

		autofs_dev_ioctl_fd_install(fd, filp);
	}

	return fd;

out:
	put_unused_fd(fd);
	return err;
}

/* Open a file descriptor on an autofs mount point */
static int autofs_dev_ioctl_openmount(struct file *fp,
				      struct autofs_sb_info *sbi,
				      struct autofs_dev_ioctl *param)
{
	const char *path;
	dev_t devid;
	int err, fd;

	/* param->path has already been checked */
	if (!param->arg1)
		return -EINVAL;

	param->ioctlfd = -1;

	path = param->path;
	devid = param->arg1;

	err = 0;
	fd = autofs_dev_ioctl_open_mountpoint(path, devid);
	if (unlikely(fd < 0)) {
		err = fd;
		goto out;
	}

	param->ioctlfd = fd;
out:
	return err;
}

/* Close file descriptor allocated above (user can also use close(2)). */
static int autofs_dev_ioctl_closemount(struct file *fp,
				       struct autofs_sb_info *sbi,
				       struct autofs_dev_ioctl *param)
{
	return sys_close(param->ioctlfd);
}

/*
 * Send "ready" status for an existing wait (either a mount or an expire
 * request).
 */
static int autofs_dev_ioctl_ready(struct file *fp,
				  struct autofs_sb_info *sbi,
				  struct autofs_dev_ioctl *param)
{
	autofs_wqt_t token;

	token = (autofs_wqt_t) param->arg1;
	return autofs4_wait_release(sbi, token, 0);
}

/*
 * Send "fail" status for an existing wait (either a mount or an expire
 * request).
 */
static int autofs_dev_ioctl_fail(struct file *fp,
				 struct autofs_sb_info *sbi,
				 struct autofs_dev_ioctl *param)
{
	autofs_wqt_t token;
	int status;

	token = (autofs_wqt_t) param->arg1;
	status = param->arg2 ? param->arg2 : -ENOENT;
	return autofs4_wait_release(sbi, token, status);
}

/*
 * Set the pipe fd for kernel communication to the daemon.
 *
 * Normally this is set at mount using an option but if we
 * are reconnecting to a busy mount then we need to use this
 * to tell the autofs mount about the new kernel pipe fd. In
 * order to protect mounts against incorrectly setting the
 * pipefd we also require that the autofs mount be catatonic.
 *
 * This also sets the process group id used to identify the
 * controlling process (eg. the owning automount(8) daemon).
 */
static int autofs_dev_ioctl_setpipefd(struct file *fp,
				      struct autofs_sb_info *sbi,
				      struct autofs_dev_ioctl *param)
{
	int pipefd;
	int err = 0;

	if (param->arg1 == -1)
		return -EINVAL;

	pipefd = param->arg1;

	mutex_lock(&sbi->wq_mutex);
	if (!sbi->catatonic) {
		mutex_unlock(&sbi->wq_mutex);
		return -EBUSY;
	} else {
		struct file *pipe = fget(pipefd);
		if (!pipe->f_op || !pipe->f_op->write) {
			err = -EPIPE;
			fput(pipe);
			goto out;
		}
		sbi->oz_pgrp = task_pgrp_nr(current);
		sbi->pipefd = pipefd;
		sbi->pipe = pipe;
		sbi->catatonic = 0;
	}
out:
	mutex_unlock(&sbi->wq_mutex);
	return err;
}

/*
 * Make the autofs mount point catatonic, no longer responsive to
 * mount requests. Also closes the kernel pipe file descriptor.
 */
static int autofs_dev_ioctl_catatonic(struct file *fp,
				      struct autofs_sb_info *sbi,
				      struct autofs_dev_ioctl *param)
{
	autofs4_catatonic_mode(sbi);
	return 0;
}

/* Set the autofs mount timeout */
static int autofs_dev_ioctl_timeout(struct file *fp,
				    struct autofs_sb_info *sbi,
				    struct autofs_dev_ioctl *param)
{
	unsigned long timeout;

	timeout = param->arg1;
	param->arg1 = sbi->exp_timeout / HZ;
	sbi->exp_timeout = timeout * HZ;
	return 0;
}

/*
 * Return the uid and gid of the last request for the mount
 *
 * When reconstructing an autofs mount tree with active mounts
 * we need to re-connect to mounts that may have used the original
 * process uid and gid (or string variations of them) for mount
 * lookups within the map entry.
 */
static int autofs_dev_ioctl_requester(struct file *fp,
				      struct autofs_sb_info *sbi,
				      struct autofs_dev_ioctl *param)
{
	struct autofs_info *ino;
	struct nameidata nd;
	const char *path;
	dev_t devid;
	int err = -ENOENT;

	if (param->size <= sizeof(*param)) {
		err = -EINVAL;
		goto out;
	}

	path = param->path;
	devid = sbi->sb->s_dev;

	param->arg1 = param->arg2 = -1;

	/* Get nameidata of the parent directory */
	err = path_lookup(path, LOOKUP_PARENT, &nd);
	if (err)
		goto out;

	err = autofs_dev_ioctl_find_super(&nd, devid);
	if (err)
		goto out_release;

	ino = autofs4_dentry_ino(nd.path.dentry);
	if (ino) {
		err = 0;
		autofs4_expire_wait(nd.path.dentry);
		spin_lock(&sbi->fs_lock);
		param->arg1 = ino->uid;
		param->arg2 = ino->gid;
		spin_unlock(&sbi->fs_lock);
	}

out_release:
	path_put(&nd.path);
out:
	return err;
}

/*
 * Call repeatedly until it returns -EAGAIN, meaning there's nothing
 * more that can be done.
 */
static int autofs_dev_ioctl_expire(struct file *fp,
				   struct autofs_sb_info *sbi,
				   struct autofs_dev_ioctl *param)
{
	struct dentry *dentry;
	struct vfsmount *mnt;
	int err = -EAGAIN;
	int how;

	how = param->arg1;
	mnt = fp->f_path.mnt;

	if (sbi->type & AUTOFS_TYPE_TRIGGER)
		dentry = autofs4_expire_direct(sbi->sb, mnt, sbi, how);
	else
		dentry = autofs4_expire_indirect(sbi->sb, mnt, sbi, how);

	if (dentry) {
		struct autofs_info *ino = autofs4_dentry_ino(dentry);

		/*
		 * This is synchronous because it makes the daemon a
		 * little easier
		*/
		err = autofs4_wait(sbi, dentry, NFY_EXPIRE);

		spin_lock(&sbi->fs_lock);
		if (ino->flags & AUTOFS_INF_MOUNTPOINT) {
			ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
			sbi->sb->s_root->d_mounted++;
		}
		ino->flags &= ~AUTOFS_INF_EXPIRING;
		complete_all(&ino->expire_complete);
		spin_unlock(&sbi->fs_lock);
		dput(dentry);
	}

	return err;
}

/* Check if autofs mount point is in use */
static int autofs_dev_ioctl_askumount(struct file *fp,
				      struct autofs_sb_info *sbi,
				      struct autofs_dev_ioctl *param)
{
	param->arg1 = 0;
	if (may_umount(fp->f_path.mnt))
		param->arg1 = 1;
	return 0;
}

/*
 * Check if the given path is a mountpoint.
 *
 * If we are supplied with the file descriptor of an autofs
 * mount we're looking for a specific mount. In this case
 * the path is considered a mountpoint if it is itself a
 * mountpoint or contains a mount, such as a multi-mount
 * without a root mount. In this case we return 1 if the
 * path is a mount point and the super magic of the covering
 * mount if there is one or 0 if it isn't a mountpoint.
 *
 * If we aren't supplied with a file descriptor then we
 * lookup the nameidata of the path and check if it is the
 * root of a mount. If a type is given we are looking for
 * a particular autofs mount and if we don't find a match
 * we return fail. If the located nameidata path is the
 * root of a mount we return 1 along with the super magic
 * of the mount or 0 otherwise.
 *
 * In both cases the the device number (as returned by
 * new_encode_dev()) is also returned.
 */
static int autofs_dev_ioctl_ismountpoint(struct file *fp,
					 struct autofs_sb_info *sbi,
					 struct autofs_dev_ioctl *param)
{
	struct nameidata nd;
	const char *path;
	unsigned int type;
	int err = -ENOENT;

	if (param->size <= sizeof(*param)) {
		err = -EINVAL;
		goto out;
	}

	path = param->path;
	type = param->arg1;

	param->arg1 = 0;
	param->arg2 = 0;

	if (!fp || param->ioctlfd == -1) {
		if (type == AUTOFS_TYPE_ANY) {
			struct super_block *sb;

			err = path_lookup(path, LOOKUP_FOLLOW, &nd);
			if (err)
				goto out;

			sb = nd.path.dentry->d_sb;
			param->arg1 = new_encode_dev(sb->s_dev);
		} else {
			struct autofs_info *ino;

			err = path_lookup(path, LOOKUP_PARENT, &nd);
			if (err)
				goto out;

			err = autofs_dev_ioctl_find_sbi_type(&nd, type);
			if (err)
				goto out_release;

			ino = autofs4_dentry_ino(nd.path.dentry);
			param->arg1 = autofs4_get_dev(ino->sbi);
		}

		err = 0;
		if (nd.path.dentry->d_inode &&
		    nd.path.mnt->mnt_root == nd.path.dentry) {
			err = 1;
			param->arg2 = nd.path.dentry->d_inode->i_sb->s_magic;
		}
	} else {
		dev_t devid = new_encode_dev(sbi->sb->s_dev);

		err = path_lookup(path, LOOKUP_PARENT, &nd);
		if (err)
			goto out;

		err = autofs_dev_ioctl_find_super(&nd, devid);
		if (err)
			goto out_release;

		param->arg1 = autofs4_get_dev(sbi);

		err = have_submounts(nd.path.dentry);

		if (nd.path.mnt->mnt_mountpoint != nd.path.mnt->mnt_root) {
			if (follow_down(&nd.path.mnt, &nd.path.dentry)) {
				struct inode *inode = nd.path.dentry->d_inode;
				param->arg2 = inode->i_sb->s_magic;
			}
		}
	}

out_release:
	path_put(&nd.path);
out:
	return err;
}

/*
 * Our range of ioctl numbers isn't 0 based so we need to shift
 * the array index by _IOC_NR(AUTOFS_CTL_IOC_FIRST) for the table
 * lookup.
 */
#define cmd_idx(cmd)	(cmd - _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST))

static ioctl_fn lookup_dev_ioctl(unsigned int cmd)
{
	static struct {
		int cmd;
		ioctl_fn fn;
	} _ioctls[] = {
		{cmd_idx(AUTOFS_DEV_IOCTL_VERSION_CMD), NULL},
		{cmd_idx(AUTOFS_DEV_IOCTL_PROTOVER_CMD),
			 autofs_dev_ioctl_protover},
		{cmd_idx(AUTOFS_DEV_IOCTL_PROTOSUBVER_CMD),
			 autofs_dev_ioctl_protosubver},
		{cmd_idx(AUTOFS_DEV_IOCTL_OPENMOUNT_CMD),
			 autofs_dev_ioctl_openmount},
		{cmd_idx(AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD),
			 autofs_dev_ioctl_closemount},
		{cmd_idx(AUTOFS_DEV_IOCTL_READY_CMD),
			 autofs_dev_ioctl_ready},
		{cmd_idx(AUTOFS_DEV_IOCTL_FAIL_CMD),
			 autofs_dev_ioctl_fail},
		{cmd_idx(AUTOFS_DEV_IOCTL_SETPIPEFD_CMD),
			 autofs_dev_ioctl_setpipefd},
		{cmd_idx(AUTOFS_DEV_IOCTL_CATATONIC_CMD),
			 autofs_dev_ioctl_catatonic},
		{cmd_idx(AUTOFS_DEV_IOCTL_TIMEOUT_CMD),
			 autofs_dev_ioctl_timeout},
		{cmd_idx(AUTOFS_DEV_IOCTL_REQUESTER_CMD),
			 autofs_dev_ioctl_requester},
		{cmd_idx(AUTOFS_DEV_IOCTL_EXPIRE_CMD),
			 autofs_dev_ioctl_expire},
		{cmd_idx(AUTOFS_DEV_IOCTL_ASKUMOUNT_CMD),
			 autofs_dev_ioctl_askumount},
		{cmd_idx(AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD),
			 autofs_dev_ioctl_ismountpoint}
	};
	unsigned int idx = cmd_idx(cmd);

	return (idx >= ARRAY_SIZE(_ioctls)) ? NULL : _ioctls[idx].fn;
}

/* ioctl dispatcher */
static int _autofs_dev_ioctl(unsigned int command, struct autofs_dev_ioctl __user *user)
{
	struct autofs_dev_ioctl *param;
	struct file *fp;
	struct autofs_sb_info *sbi;
	unsigned int cmd_first, cmd;
	ioctl_fn fn = NULL;
	int err = 0;

	/* only root can play with this */
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	cmd_first = _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST);
	cmd = _IOC_NR(command);

	if (_IOC_TYPE(command) != _IOC_TYPE(AUTOFS_DEV_IOCTL_IOC_FIRST) ||
	    cmd - cmd_first >= AUTOFS_DEV_IOCTL_IOC_COUNT) {
		return -ENOTTY;
	}

	/* Copy the parameters into kernel space. */
	param = copy_dev_ioctl(user);
	if (IS_ERR(param))
		return PTR_ERR(param);

	err = validate_dev_ioctl(command, param);
	if (err)
		goto out;

	/* The validate routine above always sets the version */
	if (cmd == AUTOFS_DEV_IOCTL_VERSION_CMD)
		goto done;

	fn = lookup_dev_ioctl(cmd);
	if (!fn) {
		AUTOFS_WARN("unknown command 0x%08x", command);
		return -ENOTTY;
	}

	fp = NULL;
	sbi = NULL;

	/*
	 * For obvious reasons the openmount can't have a file
	 * descriptor yet. We don't take a reference to the
	 * file during close to allow for immediate release.
	 */
	if (cmd != AUTOFS_DEV_IOCTL_OPENMOUNT_CMD &&
	    cmd != AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD) {
		fp = fget(param->ioctlfd);
		if (!fp) {
			if (cmd == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD)
				goto cont;
			err = -EBADF;
			goto out;
		}

		if (!fp->f_op) {
			err = -ENOTTY;
			fput(fp);
			goto out;
		}

		sbi = autofs_dev_ioctl_sbi(fp);
		if (!sbi || sbi->magic != AUTOFS_SBI_MAGIC) {
			err = -EINVAL;
			fput(fp);
			goto out;
		}

		/*
		 * Admin needs to be able to set the mount catatonic in
		 * order to be able to perform the re-open.
		 */
		if (!autofs4_oz_mode(sbi) &&
		    cmd != AUTOFS_DEV_IOCTL_CATATONIC_CMD) {
			err = -EACCES;
			fput(fp);
			goto out;
		}
	}
cont:
	err = fn(fp, sbi, param);

	if (fp)
		fput(fp);
done:
	if (err >= 0 && copy_to_user(user, param, AUTOFS_DEV_IOCTL_SIZE))
		err = -EFAULT;
out:
	free_dev_ioctl(param);
	return err;
}

static long autofs_dev_ioctl(struct file *file, uint command, ulong u)
{
	int err;
	err = _autofs_dev_ioctl(command, (struct autofs_dev_ioctl __user *) u);
	return (long) err;
}

#ifdef CONFIG_COMPAT
static long autofs_dev_ioctl_compat(struct file *file, uint command, ulong u)
{
	return (long) autofs_dev_ioctl(file, command, (ulong) compat_ptr(u));
}
#else
#define autofs_dev_ioctl_compat NULL
#endif

static const struct file_operations _dev_ioctl_fops = {
	.unlocked_ioctl	 = autofs_dev_ioctl,
	.compat_ioctl = autofs_dev_ioctl_compat,
	.owner	 = THIS_MODULE,
};

static struct miscdevice _autofs_dev_ioctl_misc = {
	.minor 		= MISC_DYNAMIC_MINOR,
	.name  		= AUTOFS_DEVICE_NAME,
	.fops  		= &_dev_ioctl_fops
};

/* Register/deregister misc character device */
int autofs_dev_ioctl_init(void)
{
	int r;

	r = misc_register(&_autofs_dev_ioctl_misc);
	if (r) {
		AUTOFS_ERROR("misc_register failed for control device");
		return r;
	}

	return 0;
}

void autofs_dev_ioctl_exit(void)
{
	misc_deregister(&_autofs_dev_ioctl_misc);
	return;
}