cregit-Linux how code gets into the kernel

Release 4.18 fs/autofs/dev-ioctl.c

Directory: fs/autofs
/*
 * 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/miscdevice.h>
#include <linux/compat.h>
#include <linux/syscalls.h>
#include <linux/magic.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.
 */


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; }

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/* * 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; }

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/* * 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; }

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/* * 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; }

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

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/* * 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; }

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/* * 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 = file_inode(f); sbi = autofs_sbi(inode->i_sb); } return sbi; }

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/* 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; }

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/* 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; }

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/* 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; }

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/* 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_mountpoint(AT_FDCWD, pathname, &path, 0); 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; }

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

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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; }

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/* * 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; }

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/* 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; }

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/* 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 ksys_close(param->ioctlfd); }

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/* * 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); }

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/* * 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); }

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Ian Kent67100.00%1100.00%
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/* * 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->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->catatonic = 0; } out: put_pid(new_pid); mutex_unlock(&sbi->wq_mutex); return err; }

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/* * 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; }

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/* 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; }

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/* * 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; }

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/* * 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); }

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/* 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; }

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/* * 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 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_mountpoint(AT_FDCWD, name, &path, LOOKUP_FOLLOW); 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; }

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/* * 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 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); return (idx >= ARRAY_SIZE(_ioctls)) ? NULL : _ioctls[idx]; }

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

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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; }

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#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)); }

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#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; }

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

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Directory: fs/autofs
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