fs/ecryptfs/read_write.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * eCryptfs: Linux filesystem encryption layer
   4  *
   5  * Copyright (C) 2007 International Business Machines Corp.
   6  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
   7  */
   8
   9 #include <linux/fs.h>
  10 #include <linux/pagemap.h>
  11 #include <linux/sched/signal.h>
  12
  13 #include "ecryptfs_kernel.h"
  14
  15 /**
  16  * ecryptfs_write_lower
  17  * @ecryptfs_inode: The eCryptfs inode
  18  * @data: Data to write
  19  * @offset: Byte offset in the lower file to which to write the data
  20  * @size: Number of bytes from @data to write at @offset in the lower
  21  *        file
  22  *
  23  * Write data to the lower file.
  24  *
  25  * Returns bytes written on success; less than zero on error
  26  */
  27 int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
  28                          loff_t offset, size_t size)
  29 {
  30         struct file *lower_file;
  31         ssize_t rc;
  32
  33         lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
  34         if (!lower_file)
  35                 return -EIO;
  36         rc = kernel_write(lower_file, data, size, &offset);
  37         mark_inode_dirty_sync(ecryptfs_inode);
  38         return rc;
  39 }
  40
  41 /**
  42  * ecryptfs_write_lower_page_segment
  43  * @ecryptfs_inode: The eCryptfs inode
  44  * @folio_for_lower: The folio containing the data to be written to the
  45  *                  lower file
  46  * @offset_in_page: The offset in the @folio_for_lower from which to
  47  *                  start writing the data
  48  * @size: The amount of data from @folio_for_lower to write to the
  49  *        lower file
  50  *
  51  * Determines the byte offset in the file for the given page and
  52  * offset within the page, maps the page, and makes the call to write
  53  * the contents of @folio_for_lower to the lower inode.
  54  *
  55  * Returns zero on success; non-zero otherwise
  56  */
  57 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
  58                                       struct folio *folio_for_lower,
  59                                       size_t offset_in_page, size_t size)
  60 {
  61         char *virt;
  62         loff_t offset;
  63         int rc;
  64
  65         offset = (loff_t)folio_for_lower->index * PAGE_SIZE + offset_in_page;
  66         virt = kmap_local_folio(folio_for_lower, 0);
  67         rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
  68         if (rc > 0)
  69                 rc = 0;
  70         kunmap_local(virt);
  71         return rc;
  72 }
  73
  74 /**
  75  * ecryptfs_write
  76  * @ecryptfs_inode: The eCryptfs file into which to write
  77  * @data: Virtual address where data to write is located
  78  * @offset: Offset in the eCryptfs file at which to begin writing the
  79  *          data from @data
  80  * @size: The number of bytes to write from @data
  81  *
  82  * Write an arbitrary amount of data to an arbitrary location in the
  83  * eCryptfs inode page cache. This is done on a page-by-page, and then
  84  * by an extent-by-extent, basis; individual extents are encrypted and
  85  * written to the lower page cache (via VFS writes). This function
  86  * takes care of all the address translation to locations in the lower
  87  * filesystem; it also handles truncate events, writing out zeros
  88  * where necessary.
  89  *
  90  * Returns zero on success; non-zero otherwise
  91  */
  92 int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
  93                    size_t size)
  94 {
  95         struct ecryptfs_crypt_stat *crypt_stat;
  96         char *ecryptfs_page_virt;
  97         loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
  98         loff_t data_offset = 0;
  99         loff_t pos;
 100         int rc = 0;
 101
 102         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 103         /*
 104          * if we are writing beyond current size, then start pos
 105          * at the current size - we'll fill in zeros from there.
 106          */
 107         if (offset > ecryptfs_file_size)
 108                 pos = ecryptfs_file_size;
 109         else
 110                 pos = offset;
 111         while (pos < (offset + size)) {
 112                 struct folio *ecryptfs_folio;
 113                 pgoff_t ecryptfs_page_idx = (pos >> PAGE_SHIFT);
 114                 size_t start_offset_in_page = (pos & ~PAGE_MASK);
 115                 size_t num_bytes = (PAGE_SIZE - start_offset_in_page);
 116                 loff_t total_remaining_bytes = ((offset + size) - pos);
 117
 118                 if (fatal_signal_pending(current)) {
 119                         rc = -EINTR;
 120                         break;
 121                 }
 122
 123                 if (num_bytes > total_remaining_bytes)
 124                         num_bytes = total_remaining_bytes;
 125                 if (pos < offset) {
 126                         /* remaining zeros to write, up to destination offset */
 127                         loff_t total_remaining_zeros = (offset - pos);
 128
 129                         if (num_bytes > total_remaining_zeros)
 130                                 num_bytes = total_remaining_zeros;
 131                 }
 132                 ecryptfs_folio = read_mapping_folio(ecryptfs_inode->i_mapping,
 133                                 ecryptfs_page_idx, NULL);
 134                 if (IS_ERR(ecryptfs_folio)) {
 135                         rc = PTR_ERR(ecryptfs_folio);
 136                         printk(KERN_ERR "%s: Error getting page at "
 137                                "index [%ld] from eCryptfs inode "
 138                                "mapping; rc = [%d]\n", __func__,
 139                                ecryptfs_page_idx, rc);
 140                         goto out;
 141                 }
 142                 folio_lock(ecryptfs_folio);
 143                 ecryptfs_page_virt = kmap_local_folio(ecryptfs_folio, 0);
 144
 145                 /*
 146                  * pos: where we're now writing, offset: where the request was
 147                  * If current pos is before request, we are filling zeros
 148                  * If we are at or beyond request, we are writing the *data*
 149                  * If we're in a fresh page beyond eof, zero it in either case
 150                  */
 151                 if (pos < offset || !start_offset_in_page) {
 152                         /* We are extending past the previous end of the file.
 153                          * Fill in zero values to the end of the page */
 154                         memset(((char *)ecryptfs_page_virt
 155                                 + start_offset_in_page), 0,
 156                                 PAGE_SIZE - start_offset_in_page);
 157                 }
 158
 159                 /* pos >= offset, we are now writing the data request */
 160                 if (pos >= offset) {
 161                         memcpy(((char *)ecryptfs_page_virt
 162                                 + start_offset_in_page),
 163                                (data + data_offset), num_bytes);
 164                         data_offset += num_bytes;
 165                 }
 166                 kunmap_local(ecryptfs_page_virt);
 167                 flush_dcache_folio(ecryptfs_folio);
 168                 folio_mark_uptodate(ecryptfs_folio);
 169                 folio_unlock(ecryptfs_folio);
 170                 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 171                         rc = ecryptfs_encrypt_page(ecryptfs_folio);
 172                 else
 173                         rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
 174                                                 ecryptfs_folio,
 175                                                 start_offset_in_page,
 176                                                 data_offset);
 177                 folio_put(ecryptfs_folio);
 178                 if (rc) {
 179                         printk(KERN_ERR "%s: Error encrypting "
 180                                "page; rc = [%d]\n", __func__, rc);
 181                         goto out;
 182                 }
 183                 pos += num_bytes;
 184         }
 185         if (pos > ecryptfs_file_size) {
 186                 i_size_write(ecryptfs_inode, pos);
 187                 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
 188                         int rc2;
 189
 190                         rc2 = ecryptfs_write_inode_size_to_metadata(
 191                                                                 ecryptfs_inode);
 192                         if (rc2) {
 193                                 printk(KERN_ERR "Problem with "
 194                                        "ecryptfs_write_inode_size_to_metadata; "
 195                                        "rc = [%d]\n", rc2);
 196                                 if (!rc)
 197                                         rc = rc2;
 198                                 goto out;
 199                         }
 200                 }
 201         }
 202 out:
 203         return rc;
 204 }
 205
 206 /**
 207  * ecryptfs_read_lower
 208  * @data: The read data is stored here by this function
 209  * @offset: Byte offset in the lower file from which to read the data
 210  * @size: Number of bytes to read from @offset of the lower file and
 211  *        store into @data
 212  * @ecryptfs_inode: The eCryptfs inode
 213  *
 214  * Read @size bytes of data at byte offset @offset from the lower
 215  * inode into memory location @data.
 216  *
 217  * Returns bytes read on success; 0 on EOF; less than zero on error
 218  */
 219 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 220                         struct inode *ecryptfs_inode)
 221 {
 222         struct file *lower_file;
 223         lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
 224         if (!lower_file)
 225                 return -EIO;
 226         return kernel_read(lower_file, data, size, &offset);
 227 }
 228
 229 /**
 230  * ecryptfs_read_lower_page_segment
 231  * @folio_for_ecryptfs: The folio into which data for eCryptfs will be
 232  *                     written
 233  * @page_index: Page index in @page_for_ecryptfs from which to start
 234  *              writing
 235  * @offset_in_page: Offset in @page_for_ecryptfs from which to start
 236  *                  writing
 237  * @size: The number of bytes to write into @page_for_ecryptfs
 238  * @ecryptfs_inode: The eCryptfs inode
 239  *
 240  * Determines the byte offset in the file for the given page and
 241  * offset within the page, maps the page, and makes the call to read
 242  * the contents of @page_for_ecryptfs from the lower inode.
 243  *
 244  * Returns zero on success; non-zero otherwise
 245  */
 246 int ecryptfs_read_lower_page_segment(struct folio *folio_for_ecryptfs,
 247                                      pgoff_t page_index,
 248                                      size_t offset_in_page, size_t size,
 249                                      struct inode *ecryptfs_inode)
 250 {
 251         char *virt;
 252         loff_t offset;
 253         int rc;
 254
 255         offset = (loff_t)page_index * PAGE_SIZE + offset_in_page;
 256         virt = kmap_local_folio(folio_for_ecryptfs, 0);
 257         rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
 258         if (rc > 0)
 259                 rc = 0;
 260         kunmap_local(virt);
 261         flush_dcache_folio(folio_for_ecryptfs);
 262         return rc;
 263 }