fs/ecryptfs/mmap.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * eCryptfs: Linux filesystem encryption layer
   4  * This is where eCryptfs coordinates the symmetric encryption and
   5  * decryption of the file data as it passes between the lower
   6  * encrypted file and the upper decrypted file.
   7  *
   8  * Copyright (C) 1997-2003 Erez Zadok
   9  * Copyright (C) 2001-2003 Stony Brook University
  10  * Copyright (C) 2004-2007 International Business Machines Corp.
  11  *   Author(s): Michael A. Halcrow <[email protected]>
  12  */
  13
  14 #include <linux/pagemap.h>
  15 #include <linux/writeback.h>
  16 #include <linux/page-flags.h>
  17 #include <linux/mount.h>
  18 #include <linux/file.h>
  19 #include <linux/scatterlist.h>
  20 #include <linux/slab.h>
  21 #include <linux/xattr.h>
  22 #include <linux/unaligned.h>
  23 #include "ecryptfs_kernel.h"
  24
  25 /*
  26  * This is where we encrypt the data and pass the encrypted data to
  27  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
  28  * entire underlying packets.
  29  */
  30 static int ecryptfs_writepages(struct address_space *mapping,
  31                 struct writeback_control *wbc)
  32 {
  33         struct folio *folio = NULL;
  34         int error;
  35
  36         while ((folio = writeback_iter(mapping, wbc, folio, &error))) {
  37                 error = ecryptfs_encrypt_page(folio);
  38                 if (error) {
  39                         ecryptfs_printk(KERN_WARNING,
  40                                 "Error encrypting folio (index [0x%.16lx])\n",
  41                                 folio->index);
  42                         folio_clear_uptodate(folio);
  43                         mapping_set_error(mapping, error);
  44                 }
  45                 folio_unlock(folio);
  46         }
  47
  48         return error;
  49 }
  50
  51 static void strip_xattr_flag(char *page_virt,
  52                              struct ecryptfs_crypt_stat *crypt_stat)
  53 {
  54         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
  55                 size_t written;
  56
  57                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
  58                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
  59                                                 &written);
  60                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
  61         }
  62 }
  63
  64 /*
  65  *   Header Extent:
  66  *     Octets 0-7:        Unencrypted file size (big-endian)
  67  *     Octets 8-15:       eCryptfs special marker
  68  *     Octets 16-19:      Flags
  69  *      Octet 16:         File format version number (between 0 and 255)
  70  *      Octets 17-18:     Reserved
  71  *      Octet 19:         Bit 1 (lsb): Reserved
  72  *                        Bit 2: Encrypted?
  73  *                        Bits 3-8: Reserved
  74  *     Octets 20-23:      Header extent size (big-endian)
  75  *     Octets 24-25:      Number of header extents at front of file
  76  *                        (big-endian)
  77  *     Octet  26:         Begin RFC 2440 authentication token packet set
  78  */
  79
  80 /**
  81  * ecryptfs_copy_up_encrypted_with_header
  82  * @folio: Sort of a ``virtual'' representation of the encrypted lower
  83  *        file. The actual lower file does not have the metadata in
  84  *        the header. This is locked.
  85  * @crypt_stat: The eCryptfs inode's cryptographic context
  86  *
  87  * The ``view'' is the version of the file that userspace winds up
  88  * seeing, with the header information inserted.
  89  */
  90 static int
  91 ecryptfs_copy_up_encrypted_with_header(struct folio *folio,
  92                                        struct ecryptfs_crypt_stat *crypt_stat)
  93 {
  94         loff_t extent_num_in_page = 0;
  95         loff_t num_extents_per_page = (PAGE_SIZE
  96                                        / crypt_stat->extent_size);
  97         int rc = 0;
  98
  99         while (extent_num_in_page < num_extents_per_page) {
 100                 loff_t view_extent_num = ((loff_t)folio->index
 101                                            * num_extents_per_page)
 102                                           + extent_num_in_page;
 103                 size_t num_header_extents_at_front =
 104                         (crypt_stat->metadata_size / crypt_stat->extent_size);
 105
 106                 if (view_extent_num < num_header_extents_at_front) {
 107                         /* This is a header extent */
 108                         char *page_virt;
 109
 110                         page_virt = kmap_local_folio(folio, 0);
 111                         memset(page_virt, 0, PAGE_SIZE);
 112                         /* TODO: Support more than one header extent */
 113                         if (view_extent_num == 0) {
 114                                 size_t written;
 115
 116                                 rc = ecryptfs_read_xattr_region(
 117                                         page_virt, folio->mapping->host);
 118                                 strip_xattr_flag(page_virt + 16, crypt_stat);
 119                                 ecryptfs_write_header_metadata(page_virt + 20,
 120                                                                crypt_stat,
 121                                                                &written);
 122                         }
 123                         kunmap_local(page_virt);
 124                         flush_dcache_folio(folio);
 125                         if (rc) {
 126                                 printk(KERN_ERR "%s: Error reading xattr "
 127                                        "region; rc = [%d]\n", __func__, rc);
 128                                 goto out;
 129                         }
 130                 } else {
 131                         /* This is an encrypted data extent */
 132                         loff_t lower_offset =
 133                                 ((view_extent_num * crypt_stat->extent_size)
 134                                  - crypt_stat->metadata_size);
 135
 136                         rc = ecryptfs_read_lower_page_segment(
 137                                 folio, (lower_offset >> PAGE_SHIFT),
 138                                 (lower_offset & ~PAGE_MASK),
 139                                 crypt_stat->extent_size, folio->mapping->host);
 140                         if (rc) {
 141                                 printk(KERN_ERR "%s: Error attempting to read "
 142                                        "extent at offset [%lld] in the lower "
 143                                        "file; rc = [%d]\n", __func__,
 144                                        lower_offset, rc);
 145                                 goto out;
 146                         }
 147                 }
 148                 extent_num_in_page++;
 149         }
 150 out:
 151         return rc;
 152 }
 153
 154 /**
 155  * ecryptfs_read_folio
 156  * @file: An eCryptfs file
 157  * @folio: Folio from eCryptfs inode mapping into which to stick the read data
 158  *
 159  * Read in a folio, decrypting if necessary.
 160  *
 161  * Returns zero on success; non-zero on error.
 162  */
 163 static int ecryptfs_read_folio(struct file *file, struct folio *folio)
 164 {
 165         struct inode *inode = folio->mapping->host;
 166         struct ecryptfs_crypt_stat *crypt_stat =
 167                 &ecryptfs_inode_to_private(inode)->crypt_stat;
 168         int err = 0;
 169
 170         if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 171                 err = ecryptfs_read_lower_page_segment(folio, folio->index, 0,
 172                                 folio_size(folio), inode);
 173         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 174                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 175                         err = ecryptfs_copy_up_encrypted_with_header(folio,
 176                                         crypt_stat);
 177                         if (err) {
 178                                 printk(KERN_ERR "%s: Error attempting to copy "
 179                                        "the encrypted content from the lower "
 180                                        "file whilst inserting the metadata "
 181                                        "from the xattr into the header; err = "
 182                                        "[%d]\n", __func__, err);
 183                                 goto out;
 184                         }
 185
 186                 } else {
 187                         err = ecryptfs_read_lower_page_segment(folio,
 188                                         folio->index, 0, folio_size(folio),
 189                                         inode);
 190                         if (err) {
 191                                 printk(KERN_ERR "Error reading page; err = "
 192                                        "[%d]\n", err);
 193                                 goto out;
 194                         }
 195                 }
 196         } else {
 197                 err = ecryptfs_decrypt_page(folio);
 198                 if (err) {
 199                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 200                                         "err = [%d]\n", err);
 201                         goto out;
 202                 }
 203         }
 204 out:
 205         ecryptfs_printk(KERN_DEBUG, "Unlocking folio with index = [0x%.16lx]\n",
 206                         folio->index);
 207         folio_end_read(folio, err == 0);
 208         return err;
 209 }
 210
 211 /*
 212  * Called with lower inode mutex held.
 213  */
 214 static int fill_zeros_to_end_of_page(struct folio *folio, unsigned int to)
 215 {
 216         struct inode *inode = folio->mapping->host;
 217         int end_byte_in_page;
 218
 219         if ((i_size_read(inode) / PAGE_SIZE) != folio->index)
 220                 goto out;
 221         end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
 222         if (to > end_byte_in_page)
 223                 end_byte_in_page = to;
 224         folio_zero_segment(folio, end_byte_in_page, PAGE_SIZE);
 225 out:
 226         return 0;
 227 }
 228
 229 /**
 230  * ecryptfs_write_begin
 231  * @file: The eCryptfs file
 232  * @mapping: The eCryptfs object
 233  * @pos: The file offset at which to start writing
 234  * @len: Length of the write
 235  * @foliop: Pointer to return the folio
 236  * @fsdata: Pointer to return fs data (unused)
 237  *
 238  * This function must zero any hole we create
 239  *
 240  * Returns zero on success; non-zero otherwise
 241  */
 242 static int ecryptfs_write_begin(struct file *file,
 243                         struct address_space *mapping,
 244                         loff_t pos, unsigned len,
 245                         struct folio **foliop, void **fsdata)
 246 {
 247         pgoff_t index = pos >> PAGE_SHIFT;
 248         struct folio *folio;
 249         loff_t prev_page_end_size;
 250         int rc = 0;
 251
 252         folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
 253                         mapping_gfp_mask(mapping));
 254         if (IS_ERR(folio))
 255                 return PTR_ERR(folio);
 256         *foliop = folio;
 257
 258         prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
 259         if (!folio_test_uptodate(folio)) {
 260                 struct ecryptfs_crypt_stat *crypt_stat =
 261                         &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
 262
 263                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 264                         rc = ecryptfs_read_lower_page_segment(
 265                                 folio, index, 0, PAGE_SIZE, mapping->host);
 266                         if (rc) {
 267                                 printk(KERN_ERR "%s: Error attempting to read "
 268                                        "lower page segment; rc = [%d]\n",
 269                                        __func__, rc);
 270                                 folio_clear_uptodate(folio);
 271                                 goto out;
 272                         } else
 273                                 folio_mark_uptodate(folio);
 274                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 275                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 276                                 rc = ecryptfs_copy_up_encrypted_with_header(
 277                                         folio, crypt_stat);
 278                                 if (rc) {
 279                                         printk(KERN_ERR "%s: Error attempting "
 280                                                "to copy the encrypted content "
 281                                                "from the lower file whilst "
 282                                                "inserting the metadata from "
 283                                                "the xattr into the header; rc "
 284                                                "= [%d]\n", __func__, rc);
 285                                         folio_clear_uptodate(folio);
 286                                         goto out;
 287                                 }
 288                                 folio_mark_uptodate(folio);
 289                         } else {
 290                                 rc = ecryptfs_read_lower_page_segment(
 291                                         folio, index, 0, PAGE_SIZE,
 292                                         mapping->host);
 293                                 if (rc) {
 294                                         printk(KERN_ERR "%s: Error reading "
 295                                                "page; rc = [%d]\n",
 296                                                __func__, rc);
 297                                         folio_clear_uptodate(folio);
 298                                         goto out;
 299                                 }
 300                                 folio_mark_uptodate(folio);
 301                         }
 302                 } else {
 303                         if (prev_page_end_size
 304                             >= i_size_read(mapping->host)) {
 305                                 folio_zero_range(folio, 0, PAGE_SIZE);
 306                                 folio_mark_uptodate(folio);
 307                         } else if (len < PAGE_SIZE) {
 308                                 rc = ecryptfs_decrypt_page(folio);
 309                                 if (rc) {
 310                                         printk(KERN_ERR "%s: Error decrypting "
 311                                                "page at index [%ld]; "
 312                                                "rc = [%d]\n",
 313                                                __func__, folio->index, rc);
 314                                         folio_clear_uptodate(folio);
 315                                         goto out;
 316                                 }
 317                                 folio_mark_uptodate(folio);
 318                         }
 319                 }
 320         }
 321         /* If creating a page or more of holes, zero them out via truncate.
 322          * Note, this will increase i_size. */
 323         if (index != 0) {
 324                 if (prev_page_end_size > i_size_read(mapping->host)) {
 325                         rc = ecryptfs_truncate(file->f_path.dentry,
 326                                                prev_page_end_size);
 327                         if (rc) {
 328                                 printk(KERN_ERR "%s: Error on attempt to "
 329                                        "truncate to (higher) offset [%lld];"
 330                                        " rc = [%d]\n", __func__,
 331                                        prev_page_end_size, rc);
 332                                 goto out;
 333                         }
 334                 }
 335         }
 336         /* Writing to a new page, and creating a small hole from start
 337          * of page?  Zero it out. */
 338         if ((i_size_read(mapping->host) == prev_page_end_size)
 339             && (pos != 0))
 340                 folio_zero_range(folio, 0, PAGE_SIZE);
 341 out:
 342         if (unlikely(rc)) {
 343                 folio_unlock(folio);
 344                 folio_put(folio);
 345         }
 346         return rc;
 347 }
 348
 349 /*
 350  * ecryptfs_write_inode_size_to_header
 351  *
 352  * Writes the lower file size to the first 8 bytes of the header.
 353  *
 354  * Returns zero on success; non-zero on error.
 355  */
 356 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 357 {
 358         char *file_size_virt;
 359         int rc;
 360
 361         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 362         if (!file_size_virt) {
 363                 rc = -ENOMEM;
 364                 goto out;
 365         }
 366         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 367         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 368                                   sizeof(u64));
 369         kfree(file_size_virt);
 370         if (rc < 0)
 371                 printk(KERN_ERR "%s: Error writing file size to header; "
 372                        "rc = [%d]\n", __func__, rc);
 373         else
 374                 rc = 0;
 375 out:
 376         return rc;
 377 }
 378
 379 struct kmem_cache *ecryptfs_xattr_cache;
 380
 381 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 382 {
 383         ssize_t size;
 384         void *xattr_virt;
 385         struct dentry *lower_dentry =
 386                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
 387         struct inode *lower_inode = d_inode(lower_dentry);
 388         int rc;
 389
 390         if (!(lower_inode->i_opflags & IOP_XATTR)) {
 391                 printk(KERN_WARNING
 392                        "No support for setting xattr in lower filesystem\n");
 393                 rc = -ENOSYS;
 394                 goto out;
 395         }
 396         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 397         if (!xattr_virt) {
 398                 rc = -ENOMEM;
 399                 goto out;
 400         }
 401         inode_lock(lower_inode);
 402         size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
 403                               xattr_virt, PAGE_SIZE);
 404         if (size < 0)
 405                 size = 8;
 406         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 407         rc = __vfs_setxattr(&nop_mnt_idmap, lower_dentry, lower_inode,
 408                             ECRYPTFS_XATTR_NAME, xattr_virt, size, 0);
 409         inode_unlock(lower_inode);
 410         if (rc)
 411                 printk(KERN_ERR "Error whilst attempting to write inode size "
 412                        "to lower file xattr; rc = [%d]\n", rc);
 413         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 414 out:
 415         return rc;
 416 }
 417
 418 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 419 {
 420         struct ecryptfs_crypt_stat *crypt_stat;
 421
 422         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 423         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 424         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 425                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 426         else
 427                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 428 }
 429
 430 /**
 431  * ecryptfs_write_end
 432  * @file: The eCryptfs file object
 433  * @mapping: The eCryptfs object
 434  * @pos: The file position
 435  * @len: The length of the data (unused)
 436  * @copied: The amount of data copied
 437  * @folio: The eCryptfs folio
 438  * @fsdata: The fsdata (unused)
 439  */
 440 static int ecryptfs_write_end(struct file *file,
 441                         struct address_space *mapping,
 442                         loff_t pos, unsigned len, unsigned copied,
 443                         struct folio *folio, void *fsdata)
 444 {
 445         pgoff_t index = pos >> PAGE_SHIFT;
 446         unsigned from = pos & (PAGE_SIZE - 1);
 447         unsigned to = from + copied;
 448         struct inode *ecryptfs_inode = mapping->host;
 449         struct ecryptfs_crypt_stat *crypt_stat =
 450                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 451         int rc;
 452
 453         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 454                         "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
 455         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 456                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
 457                                 folio, 0, to);
 458                 if (!rc) {
 459                         rc = copied;
 460                         fsstack_copy_inode_size(ecryptfs_inode,
 461                                 ecryptfs_inode_to_lower(ecryptfs_inode));
 462                 }
 463                 goto out;
 464         }
 465         if (!folio_test_uptodate(folio)) {
 466                 if (copied < PAGE_SIZE) {
 467                         rc = 0;
 468                         goto out;
 469                 }
 470                 folio_mark_uptodate(folio);
 471         }
 472         /* Fills in zeros if 'to' goes beyond inode size */
 473         rc = fill_zeros_to_end_of_page(folio, to);
 474         if (rc) {
 475                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 476                         "zeros in page with index = [0x%.16lx]\n", index);
 477                 goto out;
 478         }
 479         rc = ecryptfs_encrypt_page(folio);
 480         if (rc) {
 481                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 482                                 "index [0x%.16lx])\n", index);
 483                 goto out;
 484         }
 485         if (pos + copied > i_size_read(ecryptfs_inode)) {
 486                 i_size_write(ecryptfs_inode, pos + copied);
 487                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 488                         "[0x%.16llx]\n",
 489                         (unsigned long long)i_size_read(ecryptfs_inode));
 490         }
 491         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 492         if (rc)
 493                 printk(KERN_ERR "Error writing inode size to metadata; "
 494                        "rc = [%d]\n", rc);
 495         else
 496                 rc = copied;
 497 out:
 498         folio_unlock(folio);
 499         folio_put(folio);
 500         return rc;
 501 }
 502
 503 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 504 {
 505         struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host);
 506         int ret = bmap(lower_inode, &block);
 507
 508         if (ret)
 509                 return 0;
 510         return block;
 511 }
 512
 513 #include <linux/buffer_head.h>
 514
 515 const struct address_space_operations ecryptfs_aops = {
 516         /*
 517          * XXX: This is pretty broken for multiple reasons: ecryptfs does not
 518          * actually use buffer_heads, and ecryptfs will crash without
 519          * CONFIG_BLOCK.  But it matches the behavior before the default for
 520          * address_space_operations without the ->dirty_folio method was
 521          * cleaned up, so this is the best we can do without maintainer
 522          * feedback.
 523          */
 524 #ifdef CONFIG_BLOCK
 525         .dirty_folio    = block_dirty_folio,
 526         .invalidate_folio = block_invalidate_folio,
 527 #endif
 528         .writepages = ecryptfs_writepages,
 529         .read_folio = ecryptfs_read_folio,
 530         .write_begin = ecryptfs_write_begin,
 531         .write_end = ecryptfs_write_end,
 532         .migrate_folio = filemap_migrate_folio,
 533         .bmap = ecryptfs_bmap,
 534 };