linux/fs/autofs4/dev-ioctl.c
Eric W. Biederman 45634cd8cb userns: Support autofs4 interacing with multiple user namespaces
Use kuid_t and kgid_t in struct autofs_info and struct autofs_wait_queue.

When creating directories and symlinks default the uid and gid of
the mount requester to the global root uid and gid.  autofs4_wait
will update these fields when a mount is requested.

When generating autofsv5 packets report the uid and gid of the mount
requestor in user namespace of the process that opened the pipe,
reporting unmapped uids and gids as overflowuid and overflowgid.

In autofs_dev_ioctl_requester return the uid and gid of the last mount
requester converted into the calling processes user namespace.  When the
uid or gid don't map return overflowuid and overflowgid as appropriate,
allowing failure to find a mount requester to be distinguished from
failure to map a mount requester.

The uid and gid mount options specifying the user and group of the
root autofs inode are converted into kuid and kgid as they are parsed
defaulting to the current uid and current gid of the process that
mounts autofs.

Mounting of autofs for the present remains confined to processes in
the initial user namespace.

Cc: Ian Kent <raven@themaw.net>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2012-11-14 22:05:32 -08:00

749 lines
18 KiB
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/magic.h>
#include <linux/dcache.h>
#include <linux/uaccess.h>
#include <linux/slab.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, 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 ((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;
if (copy_from_user(&tmp, in, sizeof(tmp)))
return ERR_PTR(-EFAULT);
if (tmp.size < sizeof(tmp))
return ERR_PTR(-EINVAL);
return memdup_user(in, tmp.size);
}
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 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) {
AUTOFS_WARN("invalid device control module version "
"supplied for cmd(0x%08x)", cmd);
goto out;
}
if (param->size > sizeof(*param)) {
err = invalid_str(param->path, param->size - sizeof(*param));
if (err) {
AUTOFS_WARN(
"path string terminator missing for cmd(0x%08x)",
cmd);
goto out;
}
err = check_name(param->path);
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->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;
}
static int find_autofs_mount(const char *pathname,
struct path *res,
int test(struct path *path, void *data),
void *data)
{
struct path path;
int err = kern_path(pathname, 0, &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);
if (!err) /* already found some */
path_put(res);
*res = path;
err = 0;
}
}
if (!follow_up(&path))
break;
}
path_put(&path);
return err;
}
static int test_by_dev(struct path *path, void *p)
{
return path->dentry->d_sb->s_dev == *(dev_t *)p;
}
static int test_by_type(struct path *path, void *p)
{
struct autofs_info *ino = autofs4_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;
/*
* Find autofs super block that has the device number
* corresponding to the autofs fs we want to open.
*/
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 already been checked */
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 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->ready.token;
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->fail.token;
status = param->fail.status ? param->fail.status : -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->setpipefd.pipefd == -1)
return -EINVAL;
pipefd = param->setpipefd.pipefd;
mutex_lock(&sbi->wq_mutex);
if (!sbi->catatonic) {
mutex_unlock(&sbi->wq_mutex);
return -EBUSY;
} else {
struct file *pipe = fget(pipefd);
if (!pipe) {
err = -EBADF;
goto out;
}
if (autofs_prepare_pipe(pipe) < 0) {
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->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;
if (param->size <= sizeof(*param)) {
err = -EINVAL;
goto out;
}
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 = autofs4_dentry_ino(path.dentry);
if (ino) {
err = 0;
autofs4_expire_wait(path.dentry);
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 autofs4_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 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 path path;
const char *name;
unsigned int type;
unsigned int devid, magic;
int err = -ENOENT;
if (param->size <= sizeof(*param)) {
err = -EINVAL;
goto out;
}
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, &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 = have_submounts(path.dentry);
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 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,
.llseek = noop_llseek,
};
static struct miscdevice _autofs_dev_ioctl_misc = {
.minor = AUTOFS_MINOR,
.name = AUTOFS_DEVICE_NAME,
.fops = &_dev_ioctl_fops
};
MODULE_ALIAS_MISCDEV(AUTOFS_MINOR);
MODULE_ALIAS("devname:autofs");
/* 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;
}