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. */
  12 static 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  */
  29 static 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  */
  46 static 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  */
  75 static 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  */
 188 int 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 }