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