fs/kernfs/inode.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * fs/kernfs/inode.c - kernfs inode implementation
   4  *
   5  * Copyright (c) 2001-3 Patrick Mochel
   6  * Copyright (c) 2007 SUSE Linux Products GmbH
   7  * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
   8  */
   9
  10 #include <linux/pagemap.h>
  11 #include <linux/backing-dev.h>
  12 #include <linux/capability.h>
  13 #include <linux/errno.h>
  14 #include <linux/slab.h>
  15 #include <linux/xattr.h>
  16 #include <linux/security.h>
  17
  18 #include "kernfs-internal.h"
  19
  20 static const struct inode_operations kernfs_iops = {
  21         .permission     = kernfs_iop_permission,
  22         .setattr        = kernfs_iop_setattr,
  23         .getattr        = kernfs_iop_getattr,
  24         .listxattr      = kernfs_iop_listxattr,
  25 };
  26
  27 static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc)
  28 {
  29         static DEFINE_MUTEX(iattr_mutex);
  30         struct kernfs_iattrs *ret;
  31
  32         mutex_lock(&iattr_mutex);
  33
  34         if (kn->iattr || !alloc)
  35                 goto out_unlock;
  36
  37         kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
  38         if (!kn->iattr)
  39                 goto out_unlock;
  40
  41         /* assign default attributes */
  42         kn->iattr->ia_uid = GLOBAL_ROOT_UID;
  43         kn->iattr->ia_gid = GLOBAL_ROOT_GID;
  44
  45         ktime_get_real_ts64(&kn->iattr->ia_atime);
  46         kn->iattr->ia_mtime = kn->iattr->ia_atime;
  47         kn->iattr->ia_ctime = kn->iattr->ia_atime;
  48
  49         simple_xattrs_init(&kn->iattr->xattrs);
  50         atomic_set(&kn->iattr->nr_user_xattrs, 0);
  51         atomic_set(&kn->iattr->user_xattr_size, 0);
  52 out_unlock:
  53         ret = kn->iattr;
  54         mutex_unlock(&iattr_mutex);
  55         return ret;
  56 }
  57
  58 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
  59 {
  60         return __kernfs_iattrs(kn, 1);
  61 }
  62
  63 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
  64 {
  65         return __kernfs_iattrs(kn, 0);
  66 }
  67
  68 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
  69 {
  70         struct kernfs_iattrs *attrs;
  71         unsigned int ia_valid = iattr->ia_valid;
  72
  73         attrs = kernfs_iattrs(kn);
  74         if (!attrs)
  75                 return -ENOMEM;
  76
  77         if (ia_valid & ATTR_UID)
  78                 attrs->ia_uid = iattr->ia_uid;
  79         if (ia_valid & ATTR_GID)
  80                 attrs->ia_gid = iattr->ia_gid;
  81         if (ia_valid & ATTR_ATIME)
  82                 attrs->ia_atime = iattr->ia_atime;
  83         if (ia_valid & ATTR_MTIME)
  84                 attrs->ia_mtime = iattr->ia_mtime;
  85         if (ia_valid & ATTR_CTIME)
  86                 attrs->ia_ctime = iattr->ia_ctime;
  87         if (ia_valid & ATTR_MODE)
  88                 kn->mode = iattr->ia_mode;
  89         return 0;
  90 }
  91
  92 /**
  93  * kernfs_setattr - set iattr on a node
  94  * @kn: target node
  95  * @iattr: iattr to set
  96  *
  97  * Return: %0 on success, -errno on failure.
  98  */
  99 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 100 {
 101         int ret;
 102         struct kernfs_root *root = kernfs_root(kn);
 103
 104         down_write(&root->kernfs_iattr_rwsem);
 105         ret = __kernfs_setattr(kn, iattr);
 106         up_write(&root->kernfs_iattr_rwsem);
 107         return ret;
 108 }
 109
 110 int kernfs_iop_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 111                        struct iattr *iattr)
 112 {
 113         struct inode *inode = d_inode(dentry);
 114         struct kernfs_node *kn = inode->i_private;
 115         struct kernfs_root *root;
 116         int error;
 117
 118         if (!kn)
 119                 return -EINVAL;
 120
 121         root = kernfs_root(kn);
 122         down_write(&root->kernfs_iattr_rwsem);
 123         error = setattr_prepare(&nop_mnt_idmap, dentry, iattr);
 124         if (error)
 125                 goto out;
 126
 127         error = __kernfs_setattr(kn, iattr);
 128         if (error)
 129                 goto out;
 130
 131         /* this ignores size changes */
 132         setattr_copy(&nop_mnt_idmap, inode, iattr);
 133
 134 out:
 135         up_write(&root->kernfs_iattr_rwsem);
 136         return error;
 137 }
 138
 139 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
 140 {
 141         struct kernfs_node *kn = kernfs_dentry_node(dentry);
 142         struct kernfs_iattrs *attrs;
 143
 144         attrs = kernfs_iattrs(kn);
 145         if (!attrs)
 146                 return -ENOMEM;
 147
 148         return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
 149 }
 150
 151 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
 152 {
 153         inode->i_mode = mode;
 154         simple_inode_init_ts(inode);
 155 }
 156
 157 static inline void set_inode_attr(struct inode *inode,
 158                                   struct kernfs_iattrs *attrs)
 159 {
 160         inode->i_uid = attrs->ia_uid;
 161         inode->i_gid = attrs->ia_gid;
 162         inode_set_atime_to_ts(inode, attrs->ia_atime);
 163         inode_set_mtime_to_ts(inode, attrs->ia_mtime);
 164         inode_set_ctime_to_ts(inode, attrs->ia_ctime);
 165 }
 166
 167 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
 168 {
 169         struct kernfs_iattrs *attrs = kn->iattr;
 170
 171         inode->i_mode = kn->mode;
 172         if (attrs)
 173                 /*
 174                  * kernfs_node has non-default attributes get them from
 175                  * persistent copy in kernfs_node.
 176                  */
 177                 set_inode_attr(inode, attrs);
 178
 179         if (kernfs_type(kn) == KERNFS_DIR)
 180                 set_nlink(inode, kn->dir.subdirs + 2);
 181 }
 182
 183 int kernfs_iop_getattr(struct mnt_idmap *idmap,
 184                        const struct path *path, struct kstat *stat,
 185                        u32 request_mask, unsigned int query_flags)
 186 {
 187         struct inode *inode = d_inode(path->dentry);
 188         struct kernfs_node *kn = inode->i_private;
 189         struct kernfs_root *root = kernfs_root(kn);
 190
 191         down_read(&root->kernfs_iattr_rwsem);
 192         kernfs_refresh_inode(kn, inode);
 193         generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
 194         up_read(&root->kernfs_iattr_rwsem);
 195
 196         return 0;
 197 }
 198
 199 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
 200 {
 201         kernfs_get(kn);
 202         inode->i_private = kn;
 203         inode->i_mapping->a_ops = &ram_aops;
 204         inode->i_op = &kernfs_iops;
 205         inode->i_generation = kernfs_gen(kn);
 206
 207         set_default_inode_attr(inode, kn->mode);
 208         kernfs_refresh_inode(kn, inode);
 209
 210         /* initialize inode according to type */
 211         switch (kernfs_type(kn)) {
 212         case KERNFS_DIR:
 213                 inode->i_op = &kernfs_dir_iops;
 214                 inode->i_fop = &kernfs_dir_fops;
 215                 if (kn->flags & KERNFS_EMPTY_DIR)
 216                         make_empty_dir_inode(inode);
 217                 break;
 218         case KERNFS_FILE:
 219                 inode->i_size = kn->attr.size;
 220                 inode->i_fop = &kernfs_file_fops;
 221                 break;
 222         case KERNFS_LINK:
 223                 inode->i_op = &kernfs_symlink_iops;
 224                 break;
 225         default:
 226                 BUG();
 227         }
 228
 229         unlock_new_inode(inode);
 230 }
 231
 232 /**
 233  *      kernfs_get_inode - get inode for kernfs_node
 234  *      @sb: super block
 235  *      @kn: kernfs_node to allocate inode for
 236  *
 237  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
 238  *      allocated and basics are initialized.  New inode is returned
 239  *      locked.
 240  *
 241  *      Locking:
 242  *      Kernel thread context (may sleep).
 243  *
 244  *      Return:
 245  *      Pointer to allocated inode on success, %NULL on failure.
 246  */
 247 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 248 {
 249         struct inode *inode;
 250
 251         inode = iget_locked(sb, kernfs_ino(kn));
 252         if (inode && (inode->i_state & I_NEW))
 253                 kernfs_init_inode(kn, inode);
 254
 255         return inode;
 256 }
 257
 258 /*
 259  * The kernfs_node serves as both an inode and a directory entry for
 260  * kernfs.  To prevent the kernfs inode numbers from being freed
 261  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
 262  * super_operations.evict_inode() implementation is needed to drop that
 263  * reference upon inode destruction.
 264  */
 265 void kernfs_evict_inode(struct inode *inode)
 266 {
 267         struct kernfs_node *kn = inode->i_private;
 268
 269         truncate_inode_pages_final(&inode->i_data);
 270         clear_inode(inode);
 271         kernfs_put(kn);
 272 }
 273
 274 int kernfs_iop_permission(struct mnt_idmap *idmap,
 275                           struct inode *inode, int mask)
 276 {
 277         struct kernfs_node *kn;
 278         struct kernfs_root *root;
 279         int ret;
 280
 281         if (mask & MAY_NOT_BLOCK)
 282                 return -ECHILD;
 283
 284         kn = inode->i_private;
 285         root = kernfs_root(kn);
 286
 287         down_read(&root->kernfs_iattr_rwsem);
 288         kernfs_refresh_inode(kn, inode);
 289         ret = generic_permission(&nop_mnt_idmap, inode, mask);
 290         up_read(&root->kernfs_iattr_rwsem);
 291
 292         return ret;
 293 }
 294
 295 int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
 296                      void *value, size_t size)
 297 {
 298         struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
 299         if (!attrs)
 300                 return -ENODATA;
 301
 302         return simple_xattr_get(&attrs->xattrs, name, value, size);
 303 }
 304
 305 int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
 306                      const void *value, size_t size, int flags)
 307 {
 308         struct simple_xattr *old_xattr;
 309         struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
 310         if (!attrs)
 311                 return -ENOMEM;
 312
 313         old_xattr = simple_xattr_set(&attrs->xattrs, name, value, size, flags);
 314         if (IS_ERR(old_xattr))
 315                 return PTR_ERR(old_xattr);
 316
 317         simple_xattr_free(old_xattr);
 318         return 0;
 319 }
 320
 321 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
 322                                 struct dentry *unused, struct inode *inode,
 323                                 const char *suffix, void *value, size_t size)
 324 {
 325         const char *name = xattr_full_name(handler, suffix);
 326         struct kernfs_node *kn = inode->i_private;
 327
 328         return kernfs_xattr_get(kn, name, value, size);
 329 }
 330
 331 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
 332                                 struct mnt_idmap *idmap,
 333                                 struct dentry *unused, struct inode *inode,
 334                                 const char *suffix, const void *value,
 335                                 size_t size, int flags)
 336 {
 337         const char *name = xattr_full_name(handler, suffix);
 338         struct kernfs_node *kn = inode->i_private;
 339
 340         return kernfs_xattr_set(kn, name, value, size, flags);
 341 }
 342
 343 static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn,
 344                                      const char *full_name,
 345                                      struct simple_xattrs *xattrs,
 346                                      const void *value, size_t size, int flags)
 347 {
 348         atomic_t *sz = &kn->iattr->user_xattr_size;
 349         atomic_t *nr = &kn->iattr->nr_user_xattrs;
 350         struct simple_xattr *old_xattr;
 351         int ret;
 352
 353         if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) {
 354                 ret = -ENOSPC;
 355                 goto dec_count_out;
 356         }
 357
 358         if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) {
 359                 ret = -ENOSPC;
 360                 goto dec_size_out;
 361         }
 362
 363         old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags);
 364         if (!old_xattr)
 365                 return 0;
 366
 367         if (IS_ERR(old_xattr)) {
 368                 ret = PTR_ERR(old_xattr);
 369                 goto dec_size_out;
 370         }
 371
 372         ret = 0;
 373         size = old_xattr->size;
 374         simple_xattr_free(old_xattr);
 375 dec_size_out:
 376         atomic_sub(size, sz);
 377 dec_count_out:
 378         atomic_dec(nr);
 379         return ret;
 380 }
 381
 382 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn,
 383                                     const char *full_name,
 384                                     struct simple_xattrs *xattrs,
 385                                     const void *value, size_t size, int flags)
 386 {
 387         atomic_t *sz = &kn->iattr->user_xattr_size;
 388         atomic_t *nr = &kn->iattr->nr_user_xattrs;
 389         struct simple_xattr *old_xattr;
 390
 391         old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags);
 392         if (!old_xattr)
 393                 return 0;
 394
 395         if (IS_ERR(old_xattr))
 396                 return PTR_ERR(old_xattr);
 397
 398         atomic_sub(old_xattr->size, sz);
 399         atomic_dec(nr);
 400         simple_xattr_free(old_xattr);
 401         return 0;
 402 }
 403
 404 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,
 405                                      struct mnt_idmap *idmap,
 406                                      struct dentry *unused, struct inode *inode,
 407                                      const char *suffix, const void *value,
 408                                      size_t size, int flags)
 409 {
 410         const char *full_name = xattr_full_name(handler, suffix);
 411         struct kernfs_node *kn = inode->i_private;
 412         struct kernfs_iattrs *attrs;
 413
 414         if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR))
 415                 return -EOPNOTSUPP;
 416
 417         attrs = kernfs_iattrs(kn);
 418         if (!attrs)
 419                 return -ENOMEM;
 420
 421         if (value)
 422                 return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs,
 423                                                  value, size, flags);
 424         else
 425                 return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs,
 426                                                 value, size, flags);
 427
 428 }
 429
 430 static const struct xattr_handler kernfs_trusted_xattr_handler = {
 431         .prefix = XATTR_TRUSTED_PREFIX,
 432         .get = kernfs_vfs_xattr_get,
 433         .set = kernfs_vfs_xattr_set,
 434 };
 435
 436 static const struct xattr_handler kernfs_security_xattr_handler = {
 437         .prefix = XATTR_SECURITY_PREFIX,
 438         .get = kernfs_vfs_xattr_get,
 439         .set = kernfs_vfs_xattr_set,
 440 };
 441
 442 static const struct xattr_handler kernfs_user_xattr_handler = {
 443         .prefix = XATTR_USER_PREFIX,
 444         .get = kernfs_vfs_xattr_get,
 445         .set = kernfs_vfs_user_xattr_set,
 446 };
 447
 448 const struct xattr_handler * const kernfs_xattr_handlers[] = {
 449         &kernfs_trusted_xattr_handler,
 450         &kernfs_security_xattr_handler,
 451         &kernfs_user_xattr_handler,
 452         NULL
 453 };