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 <mahalcro@us.ibm.com>
  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 <asm/unaligned.h>
  23 #include "ecryptfs_kernel.h"
  24
  25 /**
  26  * ecryptfs_get_locked_page
  27  *
  28  * Get one page from cache or lower f/s, return error otherwise.
  29  *
  30  * Returns locked and up-to-date page (if ok), with increased
  31  * refcnt.
  32  */
  33 struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index)
  34 {
  35         struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
  36         if (!IS_ERR(page))
  37                 lock_page(page);
  38         return page;
  39 }
  40
  41 /**
  42  * ecryptfs_writepage
  43  * @page: Page that is locked before this call is made
  44  *
  45  * Returns zero on success; non-zero otherwise
  46  *
  47  * This is where we encrypt the data and pass the encrypted data to
  48  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
  49  * entire underlying packets.
  50  */
  51 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  52 {
  53         int rc;
  54
  55         rc = ecryptfs_encrypt_page(page);
  56         if (rc) {
  57                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
  58                                 "page (upper index [0x%.16lx])\n", page->index);
  59                 ClearPageUptodate(page);
  60                 goto out;
  61         }
  62         SetPageUptodate(page);
  63 out:
  64         unlock_page(page);
  65         return rc;
  66 }
  67
  68 static void strip_xattr_flag(char *page_virt,
  69                              struct ecryptfs_crypt_stat *crypt_stat)
  70 {
  71         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
  72                 size_t written;
  73
  74                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
  75                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
  76                                                 &written);
  77                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
  78         }
  79 }
  80
  81 /**
  82  *   Header Extent:
  83  *     Octets 0-7:        Unencrypted file size (big-endian)
  84  *     Octets 8-15:       eCryptfs special marker
  85  *     Octets 16-19:      Flags
  86  *      Octet 16:         File format version number (between 0 and 255)
  87  *      Octets 17-18:     Reserved
  88  *      Octet 19:         Bit 1 (lsb): Reserved
  89  *                        Bit 2: Encrypted?
  90  *                        Bits 3-8: Reserved
  91  *     Octets 20-23:      Header extent size (big-endian)
  92  *     Octets 24-25:      Number of header extents at front of file
  93  *                        (big-endian)
  94  *     Octet  26:         Begin RFC 2440 authentication token packet set
  95  */
  96
  97 /**
  98  * ecryptfs_copy_up_encrypted_with_header
  99  * @page: Sort of a ``virtual'' representation of the encrypted lower
 100  *        file. The actual lower file does not have the metadata in
 101  *        the header. This is locked.
 102  * @crypt_stat: The eCryptfs inode's cryptographic context
 103  *
 104  * The ``view'' is the version of the file that userspace winds up
 105  * seeing, with the header information inserted.
 106  */
 107 static int
 108 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 109                                        struct ecryptfs_crypt_stat *crypt_stat)
 110 {
 111         loff_t extent_num_in_page = 0;
 112         loff_t num_extents_per_page = (PAGE_SIZE
 113                                        / crypt_stat->extent_size);
 114         int rc = 0;
 115
 116         while (extent_num_in_page < num_extents_per_page) {
 117                 loff_t view_extent_num = ((((loff_t)page->index)
 118                                            * num_extents_per_page)
 119                                           + extent_num_in_page);
 120                 size_t num_header_extents_at_front =
 121                         (crypt_stat->metadata_size / crypt_stat->extent_size);
 122
 123                 if (view_extent_num < num_header_extents_at_front) {
 124                         /* This is a header extent */
 125                         char *page_virt;
 126
 127                         page_virt = kmap_atomic(page);
 128                         memset(page_virt, 0, PAGE_SIZE);
 129                         /* TODO: Support more than one header extent */
 130                         if (view_extent_num == 0) {
 131                                 size_t written;
 132
 133                                 rc = ecryptfs_read_xattr_region(
 134                                         page_virt, page->mapping->host);
 135                                 strip_xattr_flag(page_virt + 16, crypt_stat);
 136                                 ecryptfs_write_header_metadata(page_virt + 20,
 137                                                                crypt_stat,
 138                                                                &written);
 139                         }
 140                         kunmap_atomic(page_virt);
 141                         flush_dcache_page(page);
 142                         if (rc) {
 143                                 printk(KERN_ERR "%s: Error reading xattr "
 144                                        "region; rc = [%d]\n", __func__, rc);
 145                                 goto out;
 146                         }
 147                 } else {
 148                         /* This is an encrypted data extent */
 149                         loff_t lower_offset =
 150                                 ((view_extent_num * crypt_stat->extent_size)
 151                                  - crypt_stat->metadata_size);
 152
 153                         rc = ecryptfs_read_lower_page_segment(
 154                                 page, (lower_offset >> PAGE_SHIFT),
 155                                 (lower_offset & ~PAGE_MASK),
 156                                 crypt_stat->extent_size, page->mapping->host);
 157                         if (rc) {
 158                                 printk(KERN_ERR "%s: Error attempting to read "
 159                                        "extent at offset [%lld] in the lower "
 160                                        "file; rc = [%d]\n", __func__,
 161                                        lower_offset, rc);
 162                                 goto out;
 163                         }
 164                 }
 165                 extent_num_in_page++;
 166         }
 167 out:
 168         return rc;
 169 }
 170
 171 /**
 172  * ecryptfs_readpage
 173  * @file: An eCryptfs file
 174  * @page: Page from eCryptfs inode mapping into which to stick the read data
 175  *
 176  * Read in a page, decrypting if necessary.
 177  *
 178  * Returns zero on success; non-zero on error.
 179  */
 180 static int ecryptfs_readpage(struct file *file, struct page *page)
 181 {
 182         struct ecryptfs_crypt_stat *crypt_stat =
 183                 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
 184         int rc = 0;
 185
 186         if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 187                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 188                                                       PAGE_SIZE,
 189                                                       page->mapping->host);
 190         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 191                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 192                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 193                                                                     crypt_stat);
 194                         if (rc) {
 195                                 printk(KERN_ERR "%s: Error attempting to copy "
 196                                        "the encrypted content from the lower "
 197                                        "file whilst inserting the metadata "
 198                                        "from the xattr into the header; rc = "
 199                                        "[%d]\n", __func__, rc);
 200                                 goto out;
 201                         }
 202
 203                 } else {
 204                         rc = ecryptfs_read_lower_page_segment(
 205                                 page, page->index, 0, PAGE_SIZE,
 206                                 page->mapping->host);
 207                         if (rc) {
 208                                 printk(KERN_ERR "Error reading page; rc = "
 209                                        "[%d]\n", rc);
 210                                 goto out;
 211                         }
 212                 }
 213         } else {
 214                 rc = ecryptfs_decrypt_page(page);
 215                 if (rc) {
 216                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 217                                         "rc = [%d]\n", rc);
 218                         goto out;
 219                 }
 220         }
 221 out:
 222         if (rc)
 223                 ClearPageUptodate(page);
 224         else
 225                 SetPageUptodate(page);
 226         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
 227                         page->index);
 228         unlock_page(page);
 229         return rc;
 230 }
 231
 232 /**
 233  * Called with lower inode mutex held.
 234  */
 235 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 236 {
 237         struct inode *inode = page->mapping->host;
 238         int end_byte_in_page;
 239
 240         if ((i_size_read(inode) / PAGE_SIZE) != page->index)
 241                 goto out;
 242         end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
 243         if (to > end_byte_in_page)
 244                 end_byte_in_page = to;
 245         zero_user_segment(page, end_byte_in_page, PAGE_SIZE);
 246 out:
 247         return 0;
 248 }
 249
 250 /**
 251  * ecryptfs_write_begin
 252  * @file: The eCryptfs file
 253  * @mapping: The eCryptfs object
 254  * @pos: The file offset at which to start writing
 255  * @len: Length of the write
 256  * @flags: Various flags
 257  * @pagep: Pointer to return the page
 258  * @fsdata: Pointer to return fs data (unused)
 259  *
 260  * This function must zero any hole we create
 261  *
 262  * Returns zero on success; non-zero otherwise
 263  */
 264 static int ecryptfs_write_begin(struct file *file,
 265                         struct address_space *mapping,
 266                         loff_t pos, unsigned len, unsigned flags,
 267                         struct page **pagep, void **fsdata)
 268 {
 269         pgoff_t index = pos >> PAGE_SHIFT;
 270         struct page *page;
 271         loff_t prev_page_end_size;
 272         int rc = 0;
 273
 274         page = grab_cache_page_write_begin(mapping, index, flags);
 275         if (!page)
 276                 return -ENOMEM;
 277         *pagep = page;
 278
 279         prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
 280         if (!PageUptodate(page)) {
 281                 struct ecryptfs_crypt_stat *crypt_stat =
 282                         &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
 283
 284                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 285                         rc = ecryptfs_read_lower_page_segment(
 286                                 page, index, 0, PAGE_SIZE, mapping->host);
 287                         if (rc) {
 288                                 printk(KERN_ERR "%s: Error attempting to read "
 289                                        "lower page segment; rc = [%d]\n",
 290                                        __func__, rc);
 291                                 ClearPageUptodate(page);
 292                                 goto out;
 293                         } else
 294                                 SetPageUptodate(page);
 295                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 296                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 297                                 rc = ecryptfs_copy_up_encrypted_with_header(
 298                                         page, crypt_stat);
 299                                 if (rc) {
 300                                         printk(KERN_ERR "%s: Error attempting "
 301                                                "to copy the encrypted content "
 302                                                "from the lower file whilst "
 303                                                "inserting the metadata from "
 304                                                "the xattr into the header; rc "
 305                                                "= [%d]\n", __func__, rc);
 306                                         ClearPageUptodate(page);
 307                                         goto out;
 308                                 }
 309                                 SetPageUptodate(page);
 310                         } else {
 311                                 rc = ecryptfs_read_lower_page_segment(
 312                                         page, index, 0, PAGE_SIZE,
 313                                         mapping->host);
 314                                 if (rc) {
 315                                         printk(KERN_ERR "%s: Error reading "
 316                                                "page; rc = [%d]\n",
 317                                                __func__, rc);
 318                                         ClearPageUptodate(page);
 319                                         goto out;
 320                                 }
 321                                 SetPageUptodate(page);
 322                         }
 323                 } else {
 324                         if (prev_page_end_size
 325                             >= i_size_read(page->mapping->host)) {
 326                                 zero_user(page, 0, PAGE_SIZE);
 327                                 SetPageUptodate(page);
 328                         } else if (len < PAGE_SIZE) {
 329                                 rc = ecryptfs_decrypt_page(page);
 330                                 if (rc) {
 331                                         printk(KERN_ERR "%s: Error decrypting "
 332                                                "page at index [%ld]; "
 333                                                "rc = [%d]\n",
 334                                                __func__, page->index, rc);
 335                                         ClearPageUptodate(page);
 336                                         goto out;
 337                                 }
 338                                 SetPageUptodate(page);
 339                         }
 340                 }
 341         }
 342         /* If creating a page or more of holes, zero them out via truncate.
 343          * Note, this will increase i_size. */
 344         if (index != 0) {
 345                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 346                         rc = ecryptfs_truncate(file->f_path.dentry,
 347                                                prev_page_end_size);
 348                         if (rc) {
 349                                 printk(KERN_ERR "%s: Error on attempt to "
 350                                        "truncate to (higher) offset [%lld];"
 351                                        " rc = [%d]\n", __func__,
 352                                        prev_page_end_size, rc);
 353                                 goto out;
 354                         }
 355                 }
 356         }
 357         /* Writing to a new page, and creating a small hole from start
 358          * of page?  Zero it out. */
 359         if ((i_size_read(mapping->host) == prev_page_end_size)
 360             && (pos != 0))
 361                 zero_user(page, 0, PAGE_SIZE);
 362 out:
 363         if (unlikely(rc)) {
 364                 unlock_page(page);
 365                 put_page(page);
 366                 *pagep = NULL;
 367         }
 368         return rc;
 369 }
 370
 371 /**
 372  * ecryptfs_write_inode_size_to_header
 373  *
 374  * Writes the lower file size to the first 8 bytes of the header.
 375  *
 376  * Returns zero on success; non-zero on error.
 377  */
 378 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 379 {
 380         char *file_size_virt;
 381         int rc;
 382
 383         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 384         if (!file_size_virt) {
 385                 rc = -ENOMEM;
 386                 goto out;
 387         }
 388         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 389         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 390                                   sizeof(u64));
 391         kfree(file_size_virt);
 392         if (rc < 0)
 393                 printk(KERN_ERR "%s: Error writing file size to header; "
 394                        "rc = [%d]\n", __func__, rc);
 395         else
 396                 rc = 0;
 397 out:
 398         return rc;
 399 }
 400
 401 struct kmem_cache *ecryptfs_xattr_cache;
 402
 403 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 404 {
 405         ssize_t size;
 406         void *xattr_virt;
 407         struct dentry *lower_dentry =
 408                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
 409         struct inode *lower_inode = d_inode(lower_dentry);
 410         int rc;
 411
 412         if (!(lower_inode->i_opflags & IOP_XATTR)) {
 413                 printk(KERN_WARNING
 414                        "No support for setting xattr in lower filesystem\n");
 415                 rc = -ENOSYS;
 416                 goto out;
 417         }
 418         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 419         if (!xattr_virt) {
 420                 rc = -ENOMEM;
 421                 goto out;
 422         }
 423         inode_lock(lower_inode);
 424         size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
 425                               xattr_virt, PAGE_SIZE);
 426         if (size < 0)
 427                 size = 8;
 428         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 429         rc = __vfs_setxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
 430                             xattr_virt, size, 0);
 431         inode_unlock(lower_inode);
 432         if (rc)
 433                 printk(KERN_ERR "Error whilst attempting to write inode size "
 434                        "to lower file xattr; rc = [%d]\n", rc);
 435         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 436 out:
 437         return rc;
 438 }
 439
 440 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 441 {
 442         struct ecryptfs_crypt_stat *crypt_stat;
 443
 444         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 445         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 446         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 447                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 448         else
 449                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 450 }
 451
 452 /**
 453  * ecryptfs_write_end
 454  * @file: The eCryptfs file object
 455  * @mapping: The eCryptfs object
 456  * @pos: The file position
 457  * @len: The length of the data (unused)
 458  * @copied: The amount of data copied
 459  * @page: The eCryptfs page
 460  * @fsdata: The fsdata (unused)
 461  */
 462 static int ecryptfs_write_end(struct file *file,
 463                         struct address_space *mapping,
 464                         loff_t pos, unsigned len, unsigned copied,
 465                         struct page *page, void *fsdata)
 466 {
 467         pgoff_t index = pos >> PAGE_SHIFT;
 468         unsigned from = pos & (PAGE_SIZE - 1);
 469         unsigned to = from + copied;
 470         struct inode *ecryptfs_inode = mapping->host;
 471         struct ecryptfs_crypt_stat *crypt_stat =
 472                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 473         int rc;
 474
 475         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 476                         "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
 477         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 478                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
 479                                                        to);
 480                 if (!rc) {
 481                         rc = copied;
 482                         fsstack_copy_inode_size(ecryptfs_inode,
 483                                 ecryptfs_inode_to_lower(ecryptfs_inode));
 484                 }
 485                 goto out;
 486         }
 487         if (!PageUptodate(page)) {
 488                 if (copied < PAGE_SIZE) {
 489                         rc = 0;
 490                         goto out;
 491                 }
 492                 SetPageUptodate(page);
 493         }
 494         /* Fills in zeros if 'to' goes beyond inode size */
 495         rc = fill_zeros_to_end_of_page(page, to);
 496         if (rc) {
 497                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 498                         "zeros in page with index = [0x%.16lx]\n", index);
 499                 goto out;
 500         }
 501         rc = ecryptfs_encrypt_page(page);
 502         if (rc) {
 503                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 504                                 "index [0x%.16lx])\n", index);
 505                 goto out;
 506         }
 507         if (pos + copied > i_size_read(ecryptfs_inode)) {
 508                 i_size_write(ecryptfs_inode, pos + copied);
 509                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 510                         "[0x%.16llx]\n",
 511                         (unsigned long long)i_size_read(ecryptfs_inode));
 512         }
 513         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 514         if (rc)
 515                 printk(KERN_ERR "Error writing inode size to metadata; "
 516                        "rc = [%d]\n", rc);
 517         else
 518                 rc = copied;
 519 out:
 520         unlock_page(page);
 521         put_page(page);
 522         return rc;
 523 }
 524
 525 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 526 {
 527         struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host);
 528         int ret = bmap(lower_inode, &block);
 529
 530         if (ret)
 531                 return 0;
 532         return block;
 533 }
 534
 535 const struct address_space_operations ecryptfs_aops = {
 536         .writepage = ecryptfs_writepage,
 537         .readpage = ecryptfs_readpage,
 538         .write_begin = ecryptfs_write_begin,
 539         .write_end = ecryptfs_write_end,
 540         .bmap = ecryptfs_bmap,
 541 };