// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2008 Red Hat, Inc. All rights reserved.
 * Copyright 2008 Ian Kent <raven@themaw.net>
 */

#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/compat.h>
#include <linux/fdtable.h>
#include <linux/magic.h>
#include <linux/nospec.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 service shutdown.
 */

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, size_t size)
{
        if (memchr(str, 0, size))
                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 ((param->ver_major != AUTOFS_DEV_IOCTL_VERSION_MAJOR) ||
            (param->ver_minor > AUTOFS_DEV_IOCTL_VERSION_MINOR)) {
                pr_warn("ioctl control interface version mismatch: "
                        "kernel(%u.%u), user(%u.%u), cmd(0x%08x)\n",
                        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, *res;

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

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

        if (tmp.size > AUTOFS_DEV_IOCTL_SIZE + PATH_MAX)
                return ERR_PTR(-ENAMETOOLONG);

        res = memdup_user(in, tmp.size);
        if (!IS_ERR(res))
                res->size = tmp.size;

        return res;
}

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

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

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

        if (param->size > AUTOFS_DEV_IOCTL_SIZE) {
                err = invalid_str(param->path, param->size - AUTOFS_DEV_IOCTL_SIZE);
                if (err) {
                        pr_warn(
                          "path string terminator missing for cmd(0x%08x)\n",
                          cmd);
                        goto out;
                }

                err = check_name(param->path);
                if (err) {
                        pr_warn("invalid path supplied for cmd(0x%08x)\n",
                                cmd);
                        goto out;
                }
        } else {
                unsigned int inr = _IOC_NR(cmd);

                if (inr == AUTOFS_DEV_IOCTL_OPENMOUNT_CMD ||
                    inr == AUTOFS_DEV_IOCTL_REQUESTER_CMD ||
                    inr == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD) {
                        err = -EINVAL;
                        goto out;
                }
        }

        err = 0;
out:
        return err;
}

/* Return autofs dev ioctl version */
static int autofs_dev_ioctl_version(struct file *fp,
                                    struct autofs_sb_info *sbi,
                                    struct autofs_dev_ioctl *param)
{
        /* This should have already been set. */
        param->ver_major = AUTOFS_DEV_IOCTL_VERSION_MAJOR;
        param->ver_minor = AUTOFS_DEV_IOCTL_VERSION_MINOR;
        return 0;
}

/* 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->protover.version = 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->protosubver.sub_version = sbi->sub_version;
        return 0;
}

/* Find the topmost mount satisfying test() */
static int find_autofs_mount(const char *pathname,
                             struct path *res,
                             int test(const struct path *path, void *data),
                             void *data)
{
        struct path path;
        int err;

        err = kern_path(pathname, LOOKUP_MOUNTPOINT, &path);
        if (err)
                return err;
        err = -ENOENT;
        while (path.dentry == path.mnt->mnt_root) {
                if (path.dentry->d_sb->s_magic == AUTOFS_SUPER_MAGIC) {
                        if (test(&path, data)) {
                                path_get(&path);
                                *res = path;
                                err = 0;
                                break;
                        }
                }
                if (!follow_up(&path))
                        break;
        }
        path_put(&path);
        return err;
}

static int test_by_dev(const struct path *path, void *p)
{
        return path->dentry->d_sb->s_dev == *(dev_t *)p;
}

static int test_by_type(const struct path *path, void *p)
{
        struct autofs_info *ino = autofs_dentry_ino(path->dentry);

        return ino && ino->sbi->type & *(unsigned *)p;
}

/*
 * 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 *name, dev_t devid)
{
        int err, fd;

        fd = get_unused_fd_flags(O_CLOEXEC);
        if (likely(fd >= 0)) {
                struct file *filp;
                struct path path;

                err = find_autofs_mount(name, &path, test_by_dev, &devid);
                if (err)
                        goto out;

                filp = dentry_open(&path, O_RDONLY, current_cred());
                path_put(&path);
                if (IS_ERR(filp)) {
                        err = PTR_ERR(filp);
                        goto out;
                }

                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 been checked in validate_dev_ioctl() */

        if (!param->openmount.devid)
                return -EINVAL;

        param->ioctlfd = -1;

        path = param->path;
        devid = new_decode_dev(param->openmount.devid);

        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 close_fd(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->ready.token;
        return autofs_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->fail.token;
        status = param->fail.status < 0 ? param->fail.status : -ENOENT;
        return autofs_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;
        struct pid *new_pid = NULL;

        if (param->setpipefd.pipefd == -1)
                return -EINVAL;

        pipefd = param->setpipefd.pipefd;

        mutex_lock(&sbi->wq_mutex);
        if (!(sbi->flags & AUTOFS_SBI_CATATONIC)) {
                mutex_unlock(&sbi->wq_mutex);
                return -EBUSY;
        } else {
                struct file *pipe;

                new_pid = get_task_pid(current, PIDTYPE_PGID);

                if (ns_of_pid(new_pid) != ns_of_pid(sbi->oz_pgrp)) {
                        pr_warn("not allowed to change PID namespace\n");
                        err = -EINVAL;
                        goto out;
                }

                pipe = fget(pipefd);
                if (!pipe) {
                        err = -EBADF;
                        goto out;
                }
                if (autofs_prepare_pipe(pipe) < 0) {
                        err = -EPIPE;
                        fput(pipe);
                        goto out;
                }
                swap(sbi->oz_pgrp, new_pid);
                sbi->pipefd = pipefd;
                sbi->pipe = pipe;
                sbi->flags &= ~AUTOFS_SBI_CATATONIC;
        }
out:
        put_pid(new_pid);
        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)
{
        autofs_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->timeout.timeout;
        param->timeout.timeout = 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 path path;
        dev_t devid;
        int err = -ENOENT;

        /* param->path has been checked in validate_dev_ioctl() */

        devid = sbi->sb->s_dev;

        param->requester.uid = param->requester.gid = -1;

        err = find_autofs_mount(param->path, &path, test_by_dev, &devid);
        if (err)
                goto out;

        ino = autofs_dentry_ino(path.dentry);
        if (ino) {
                err = 0;
                autofs_expire_wait(&path, 0);
                spin_lock(&sbi->fs_lock);
                param->requester.uid =
                        from_kuid_munged(current_user_ns(), ino->uid);
                param->requester.gid =
                        from_kgid_munged(current_user_ns(), ino->gid);
                spin_unlock(&sbi->fs_lock);
        }
        path_put(&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 vfsmount *mnt;
        int how;

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

        return autofs_do_expire_multi(sbi->sb, mnt, sbi, how);
}

/* 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->askumount.may_umount = 0;
        if (may_umount(fp->f_path.mnt))
                param->askumount.may_umount = 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 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 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 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 path path;
        const char *name;
        unsigned int type;
        unsigned int devid, magic;
        int err = -ENOENT;

        /* param->path has been checked in validate_dev_ioctl() */

        name = param->path;
        type = param->ismountpoint.in.type;

        param->ismountpoint.out.devid = devid = 0;
        param->ismountpoint.out.magic = magic = 0;

        if (!fp || param->ioctlfd == -1) {
                if (autofs_type_any(type))
                        err = kern_path(name, LOOKUP_FOLLOW | LOOKUP_MOUNTPOINT,
                                        &path);
                else
                        err = find_autofs_mount(name, &path,
                                                test_by_type, &type);
                if (err)
                        goto out;
                devid = new_encode_dev(path.dentry->d_sb->s_dev);
                err = 0;
                if (path.mnt->mnt_root == path.dentry) {
                        err = 1;
                        magic = path.dentry->d_sb->s_magic;
                }
        } else {
                dev_t dev = sbi->sb->s_dev;

                err = find_autofs_mount(name, &path, test_by_dev, &dev);
                if (err)
                        goto out;

                devid = new_encode_dev(dev);

                err = path_has_submounts(&path);

                if (follow_down_one(&path))
                        magic = path.dentry->d_sb->s_magic;
        }

        param->ismountpoint.out.devid = devid;
        param->ismountpoint.out.magic = magic;
        path_put(&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 const ioctl_fn _ioctls[] = {
                autofs_dev_ioctl_version,
                autofs_dev_ioctl_protover,
                autofs_dev_ioctl_protosubver,
                autofs_dev_ioctl_openmount,
                autofs_dev_ioctl_closemount,
                autofs_dev_ioctl_ready,
                autofs_dev_ioctl_fail,
                autofs_dev_ioctl_setpipefd,
                autofs_dev_ioctl_catatonic,
                autofs_dev_ioctl_timeout,
                autofs_dev_ioctl_requester,
                autofs_dev_ioctl_expire,
                autofs_dev_ioctl_askumount,
                autofs_dev_ioctl_ismountpoint,
        };
        unsigned int idx = cmd_idx(cmd);

        if (idx >= ARRAY_SIZE(_ioctls))
                return NULL;
        idx = array_index_nospec(idx, ARRAY_SIZE(_ioctls));
        return _ioctls[idx];
}

/* 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;

        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;
        }

        /* Only root can use ioctls other than AUTOFS_DEV_IOCTL_VERSION_CMD
         * and AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD
         */
        if (cmd != AUTOFS_DEV_IOCTL_VERSION_CMD &&
            cmd != AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD &&
            !capable(CAP_SYS_ADMIN))
                return -EPERM;

        /* 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;

        fn = lookup_dev_ioctl(cmd);
        if (!fn) {
                pr_warn("unknown command 0x%08x\n", command);
                err = -ENOTTY;
                goto out;
        }

        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,
         * and the same for retrieving ioctl version.
         */
        if (cmd != AUTOFS_DEV_IOCTL_VERSION_CMD &&
            cmd != AUTOFS_DEV_IOCTL_OPENMOUNT_CMD &&
            cmd != AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD) {
                struct super_block *sb;

                fp = fget(param->ioctlfd);
                if (!fp) {
                        if (cmd == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD)
                                goto cont;
                        err = -EBADF;
                        goto out;
                }

                sb = file_inode(fp)->i_sb;
                if (sb->s_type != &autofs_fs_type) {
                        err = -EINVAL;
                        fput(fp);
                        goto out;
                }
                sbi = autofs_sbi(sb);

                /*
                 * Admin needs to be able to set the mount catatonic in
                 * order to be able to perform the re-open.
                 */
                if (!autofs_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);
        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, unsigned int command,
                             unsigned long 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, unsigned int command,
                                    unsigned long u)
{
        return autofs_dev_ioctl(file, command, (unsigned long) 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,
        .llseek = noop_llseek,
};

static struct miscdevice _autofs_dev_ioctl_misc = {
        .minor          = AUTOFS_MINOR,
        .name           = AUTOFS_DEVICE_NAME,
        .fops           = &_dev_ioctl_fops,
        .mode           = 0644,
};

MODULE_ALIAS_MISCDEV(AUTOFS_MINOR);
MODULE_ALIAS("devname:autofs");

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

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

        return 0;
}

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