kernel/security/tomoyo/mount.c

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