LXR linux/security/tomoyo/mount.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * security/tomoyo/mount.c
   4 *
   5 * Copyright (C) 2005-2011  NTT DATA CORPORATION
   6 */
   7
   8#include <linux/slab.h>
   9#include <uapi/linux/mount.h>
  10#include "common.h"
  11
  12/* String table for special mount operations. */
  13static const char * const tomoyo_mounts[TOMOYO_MAX_SPECIAL_MOUNT] = {
  14        [TOMOYO_MOUNT_BIND]            = "--bind",
  15        [TOMOYO_MOUNT_MOVE]            = "--move",
  16        [TOMOYO_MOUNT_REMOUNT]         = "--remount",
  17        [TOMOYO_MOUNT_MAKE_UNBINDABLE] = "--make-unbindable",
  18        [TOMOYO_MOUNT_MAKE_PRIVATE]    = "--make-private",
  19        [TOMOYO_MOUNT_MAKE_SLAVE]      = "--make-slave",
  20        [TOMOYO_MOUNT_MAKE_SHARED]     = "--make-shared",
  21};
  22
  23/**
  24 * tomoyo_audit_mount_log - Audit mount log.
  25 *
  26 * @r: Pointer to "struct tomoyo_request_info".
  27 *
  28 * Returns 0 on success, negative value otherwise.
  29 */
  30static int tomoyo_audit_mount_log(struct tomoyo_request_info *r)
  31{
  32        return tomoyo_supervisor(r, "file mount %s %s %s 0x%lX\n",
  33                                 r->param.mount.dev->name,
  34                                 r->param.mount.dir->name,
  35                                 r->param.mount.type->name,
  36                                 r->param.mount.flags);
  37}
  38
  39/**
  40 * tomoyo_check_mount_acl - Check permission for path path path number operation.
  41 *
  42 * @r:   Pointer to "struct tomoyo_request_info".
  43 * @ptr: Pointer to "struct tomoyo_acl_info".
  44 *
  45 * Returns true if granted, false otherwise.
  46 */
  47static bool tomoyo_check_mount_acl(struct tomoyo_request_info *r,
  48                                   const struct tomoyo_acl_info *ptr)
  49{
  50        const struct tomoyo_mount_acl *acl =
  51                container_of(ptr, typeof(*acl), head);
  52
  53        return tomoyo_compare_number_union(r->param.mount.flags,
  54                                           &acl->flags) &&
  55                tomoyo_compare_name_union(r->param.mount.type,
  56                                          &acl->fs_type) &&
  57                tomoyo_compare_name_union(r->param.mount.dir,
  58                                          &acl->dir_name) &&
  59                (!r->param.mount.need_dev ||
  60                 tomoyo_compare_name_union(r->param.mount.dev,
  61                                           &acl->dev_name));
  62}
  63
  64/**
  65 * tomoyo_mount_acl - Check permission for mount() operation.
  66 *
  67 * @r:        Pointer to "struct tomoyo_request_info".
  68 * @dev_name: Name of device file. Maybe NULL.
  69 * @dir:      Pointer to "struct path".
  70 * @type:     Name of filesystem type.
  71 * @flags:    Mount options.
  72 *
  73 * Returns 0 on success, negative value otherwise.
  74 *
  75 * Caller holds tomoyo_read_lock().
  76 */
  77static int tomoyo_mount_acl(struct tomoyo_request_info *r,
  78                            const char *dev_name,
  79                            const struct path *dir, const char *type,
  80                            unsigned long flags)
  81{
  82        struct tomoyo_obj_info obj = { };
  83        struct path path;
  84        struct file_system_type *fstype = NULL;
  85        const char *requested_type = NULL;
  86        const char *requested_dir_name = NULL;
  87        const char *requested_dev_name = NULL;
  88        struct tomoyo_path_info rtype;
  89        struct tomoyo_path_info rdev;
  90        struct tomoyo_path_info rdir;
  91        int need_dev = 0;
  92        int error = -ENOMEM;
  93
  94        r->obj = &obj;
  95
  96        /* Get fstype. */
  97        requested_type = tomoyo_encode(type);
  98        if (!requested_type)
  99                goto out;
 100        rtype.name = requested_type;
 101        tomoyo_fill_path_info(&rtype);
 102
 103        /* Get mount point. */
 104        obj.path2 = *dir;
 105        requested_dir_name = tomoyo_realpath_from_path(dir);
 106        if (!requested_dir_name) {
 107                error = -ENOMEM;
 108                goto out;
 109        }
 110        rdir.name = requested_dir_name;
 111        tomoyo_fill_path_info(&rdir);
 112
 113        /* Compare fs name. */
 114        if (type == tomoyo_mounts[TOMOYO_MOUNT_REMOUNT]) {
 115                /* dev_name is ignored. */
 116        } else if (type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE] ||
 117                   type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE] ||
 118                   type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE] ||
 119                   type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED]) {
 120                /* dev_name is ignored. */
 121        } else if (type == tomoyo_mounts[TOMOYO_MOUNT_BIND] ||
 122                   type == tomoyo_mounts[TOMOYO_MOUNT_MOVE]) {
 123                need_dev = -1; /* dev_name is a directory */
 124        } else {
 125                fstype = get_fs_type(type);
 126                if (!fstype) {
 127                        error = -ENODEV;
 128                        goto out;
 129                }
 130                if (fstype->fs_flags & FS_REQUIRES_DEV)
 131                        /* dev_name is a block device file. */
 132                        need_dev = 1;
 133        }
 134        if (need_dev) {
 135                /* Get mount point or device file. */
 136                if (!dev_name || kern_path(dev_name, LOOKUP_FOLLOW, &path)) {
 137                        error = -ENOENT;
 138                        goto out;
 139                }
 140                obj.path1 = path;
 141                requested_dev_name = tomoyo_realpath_from_path(&path);
 142                if (!requested_dev_name) {
 143                        error = -ENOENT;
 144                        goto out;
 145                }
 146        } else {
 147                /* Map dev_name to "<NULL>" if no dev_name given. */
 148                if (!dev_name)
 149                        dev_name = "<NULL>";
 150                requested_dev_name = tomoyo_encode(dev_name);
 151                if (!requested_dev_name) {
 152                        error = -ENOMEM;
 153                        goto out;
 154                }
 155        }
 156        rdev.name = requested_dev_name;
 157        tomoyo_fill_path_info(&rdev);
 158        r->param_type = TOMOYO_TYPE_MOUNT_ACL;
 159        r->param.mount.need_dev = need_dev;
 160        r->param.mount.dev = &rdev;
 161        r->param.mount.dir = &rdir;
 162        r->param.mount.type = &rtype;
 163        r->param.mount.flags = flags;
 164        do {
 165                tomoyo_check_acl(r, tomoyo_check_mount_acl);
 166                error = tomoyo_audit_mount_log(r);
 167        } while (error == TOMOYO_RETRY_REQUEST);
 168 out:
 169        kfree(requested_dev_name);
 170        kfree(requested_dir_name);
 171        if (fstype)
 172                put_filesystem(fstype);
 173        kfree(requested_type);
 174        /* Drop refcount obtained by kern_path(). */
 175        if (obj.path1.dentry)
 176                path_put(&obj.path1);
 177        return error;
 178}
 179
 180/**
 181 * tomoyo_mount_permission - Check permission for mount() operation.
 182 *
 183 * @dev_name:  Name of device file. Maybe NULL.
 184 * @path:      Pointer to "struct path".
 185 * @type:      Name of filesystem type. Maybe NULL.
 186 * @flags:     Mount options.
 187 * @data_page: Optional data. Maybe NULL.
 188 *
 189 * Returns 0 on success, negative value otherwise.
 190 */
 191int tomoyo_mount_permission(const char *dev_name, const struct path *path,
 192                            const char *type, unsigned long flags,
 193                            void *data_page)
 194{
 195        struct tomoyo_request_info r;
 196        int error;
 197        int idx;
 198
 199        if (tomoyo_init_request_info(&r, NULL, TOMOYO_MAC_FILE_MOUNT)
 200            == TOMOYO_CONFIG_DISABLED)
 201                return 0;
 202        if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
 203                flags &= ~MS_MGC_MSK;
 204        if (flags & MS_REMOUNT) {
 205                type = tomoyo_mounts[TOMOYO_MOUNT_REMOUNT];
 206                flags &= ~MS_REMOUNT;
 207        } else if (flags & MS_BIND) {
 208                type = tomoyo_mounts[TOMOYO_MOUNT_BIND];
 209                flags &= ~MS_BIND;
 210        } else if (flags & MS_SHARED) {
 211                if (flags & (MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
 212                        return -EINVAL;
 213                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED];
 214                flags &= ~MS_SHARED;
 215        } else if (flags & MS_PRIVATE) {
 216                if (flags & (MS_SHARED | MS_SLAVE | MS_UNBINDABLE))
 217                        return -EINVAL;
 218                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE];
 219                flags &= ~MS_PRIVATE;
 220        } else if (flags & MS_SLAVE) {
 221                if (flags & (MS_SHARED | MS_PRIVATE | MS_UNBINDABLE))
 222                        return -EINVAL;
 223                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE];
 224                flags &= ~MS_SLAVE;
 225        } else if (flags & MS_UNBINDABLE) {
 226                if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE))
 227                        return -EINVAL;
 228                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE];
 229                flags &= ~MS_UNBINDABLE;
 230        } else if (flags & MS_MOVE) {
 231                type = tomoyo_mounts[TOMOYO_MOUNT_MOVE];
 232                flags &= ~MS_MOVE;
 233        }
 234        if (!type)
 235                type = "<NULL>";
 236        idx = tomoyo_read_lock();
 237        error = tomoyo_mount_acl(&r, dev_name, path, type, flags);
 238        tomoyo_read_unlock(idx);
 239        return error;
 240}
 241