fs/ecryptfs/read_write.c

   1 /**
   2  * eCryptfs: Linux filesystem encryption layer
   3  *
   4  * Copyright (C) 2007 International Business Machines Corp.
   5  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation; either version 2 of the
  10  * License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  20  * 02111-1307, USA.
  21  */
  22
  23 #include <linux/fs.h>
  24 #include <linux/pagemap.h>
  25 #include <linux/sched/signal.h>
  26
  27 #include "ecryptfs_kernel.h"
  28
  29 /**
  30  * ecryptfs_write_lower
  31  * @ecryptfs_inode: The eCryptfs inode
  32  * @data: Data to write
  33  * @offset: Byte offset in the lower file to which to write the data
  34  * @size: Number of bytes from @data to write at @offset in the lower
  35  *        file
  36  *
  37  * Write data to the lower file.
  38  *
  39  * Returns bytes written on success; less than zero on error
  40  */
  41 int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
  42                          loff_t offset, size_t size)
  43 {
  44         struct file *lower_file;
  45         ssize_t rc;
  46
  47         lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
  48         if (!lower_file)
  49                 return -EIO;
  50         rc = kernel_write(lower_file, data, size, offset);
  51         mark_inode_dirty_sync(ecryptfs_inode);
  52         return rc;
  53 }
  54
  55 /**
  56  * ecryptfs_write_lower_page_segment
  57  * @ecryptfs_inode: The eCryptfs inode
  58  * @page_for_lower: The page containing the data to be written to the
  59  *                  lower file
  60  * @offset_in_page: The offset in the @page_for_lower from which to
  61  *                  start writing the data
  62  * @size: The amount of data from @page_for_lower to write to the
  63  *        lower file
  64  *
  65  * Determines the byte offset in the file for the given page and
  66  * offset within the page, maps the page, and makes the call to write
  67  * the contents of @page_for_lower to the lower inode.
  68  *
  69  * Returns zero on success; non-zero otherwise
  70  */
  71 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
  72                                       struct page *page_for_lower,
  73                                       size_t offset_in_page, size_t size)
  74 {
  75         char *virt;
  76         loff_t offset;
  77         int rc;
  78
  79         offset = ((((loff_t)page_for_lower->index) << PAGE_SHIFT)
  80                   + offset_in_page);
  81         virt = kmap(page_for_lower);
  82         rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
  83         if (rc > 0)
  84                 rc = 0;
  85         kunmap(page_for_lower);
  86         return rc;
  87 }
  88
  89 /**
  90  * ecryptfs_write
  91  * @ecryptfs_inode: The eCryptfs file into which to write
  92  * @data: Virtual address where data to write is located
  93  * @offset: Offset in the eCryptfs file at which to begin writing the
  94  *          data from @data
  95  * @size: The number of bytes to write from @data
  96  *
  97  * Write an arbitrary amount of data to an arbitrary location in the
  98  * eCryptfs inode page cache. This is done on a page-by-page, and then
  99  * by an extent-by-extent, basis; individual extents are encrypted and
 100  * written to the lower page cache (via VFS writes). This function
 101  * takes care of all the address translation to locations in the lower
 102  * filesystem; it also handles truncate events, writing out zeros
 103  * where necessary.
 104  *
 105  * Returns zero on success; non-zero otherwise
 106  */
 107 int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
 108                    size_t size)
 109 {
 110         struct page *ecryptfs_page;
 111         struct ecryptfs_crypt_stat *crypt_stat;
 112         char *ecryptfs_page_virt;
 113         loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
 114         loff_t data_offset = 0;
 115         loff_t pos;
 116         int rc = 0;
 117
 118         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 119         /*
 120          * if we are writing beyond current size, then start pos
 121          * at the current size - we'll fill in zeros from there.
 122          */
 123         if (offset > ecryptfs_file_size)
 124                 pos = ecryptfs_file_size;
 125         else
 126                 pos = offset;
 127         while (pos < (offset + size)) {
 128                 pgoff_t ecryptfs_page_idx = (pos >> PAGE_SHIFT);
 129                 size_t start_offset_in_page = (pos & ~PAGE_MASK);
 130                 size_t num_bytes = (PAGE_SIZE - start_offset_in_page);
 131                 loff_t total_remaining_bytes = ((offset + size) - pos);
 132
 133                 if (fatal_signal_pending(current)) {
 134                         rc = -EINTR;
 135                         break;
 136                 }
 137
 138                 if (num_bytes > total_remaining_bytes)
 139                         num_bytes = total_remaining_bytes;
 140                 if (pos < offset) {
 141                         /* remaining zeros to write, up to destination offset */
 142                         loff_t total_remaining_zeros = (offset - pos);
 143
 144                         if (num_bytes > total_remaining_zeros)
 145                                 num_bytes = total_remaining_zeros;
 146                 }
 147                 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
 148                                                          ecryptfs_page_idx);
 149                 if (IS_ERR(ecryptfs_page)) {
 150                         rc = PTR_ERR(ecryptfs_page);
 151                         printk(KERN_ERR "%s: Error getting page at "
 152                                "index [%ld] from eCryptfs inode "
 153                                "mapping; rc = [%d]\n", __func__,
 154                                ecryptfs_page_idx, rc);
 155                         goto out;
 156                 }
 157                 ecryptfs_page_virt = kmap_atomic(ecryptfs_page);
 158
 159                 /*
 160                  * pos: where we're now writing, offset: where the request was
 161                  * If current pos is before request, we are filling zeros
 162                  * If we are at or beyond request, we are writing the *data*
 163                  * If we're in a fresh page beyond eof, zero it in either case
 164                  */
 165                 if (pos < offset || !start_offset_in_page) {
 166                         /* We are extending past the previous end of the file.
 167                          * Fill in zero values to the end of the page */
 168                         memset(((char *)ecryptfs_page_virt
 169                                 + start_offset_in_page), 0,
 170                                 PAGE_SIZE - start_offset_in_page);
 171                 }
 172
 173                 /* pos >= offset, we are now writing the data request */
 174                 if (pos >= offset) {
 175                         memcpy(((char *)ecryptfs_page_virt
 176                                 + start_offset_in_page),
 177                                (data + data_offset), num_bytes);
 178                         data_offset += num_bytes;
 179                 }
 180                 kunmap_atomic(ecryptfs_page_virt);
 181                 flush_dcache_page(ecryptfs_page);
 182                 SetPageUptodate(ecryptfs_page);
 183                 unlock_page(ecryptfs_page);
 184                 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 185                         rc = ecryptfs_encrypt_page(ecryptfs_page);
 186                 else
 187                         rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
 188                                                 ecryptfs_page,
 189                                                 start_offset_in_page,
 190                                                 data_offset);
 191                 put_page(ecryptfs_page);
 192                 if (rc) {
 193                         printk(KERN_ERR "%s: Error encrypting "
 194                                "page; rc = [%d]\n", __func__, rc);
 195                         goto out;
 196                 }
 197                 pos += num_bytes;
 198         }
 199         if (pos > ecryptfs_file_size) {
 200                 i_size_write(ecryptfs_inode, pos);
 201                 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
 202                         int rc2;
 203
 204                         rc2 = ecryptfs_write_inode_size_to_metadata(
 205                                                                 ecryptfs_inode);
 206                         if (rc2) {
 207                                 printk(KERN_ERR "Problem with "
 208                                        "ecryptfs_write_inode_size_to_metadata; "
 209                                        "rc = [%d]\n", rc2);
 210                                 if (!rc)
 211                                         rc = rc2;
 212                                 goto out;
 213                         }
 214                 }
 215         }
 216 out:
 217         return rc;
 218 }
 219
 220 /**
 221  * ecryptfs_read_lower
 222  * @data: The read data is stored here by this function
 223  * @offset: Byte offset in the lower file from which to read the data
 224  * @size: Number of bytes to read from @offset of the lower file and
 225  *        store into @data
 226  * @ecryptfs_inode: The eCryptfs inode
 227  *
 228  * Read @size bytes of data at byte offset @offset from the lower
 229  * inode into memory location @data.
 230  *
 231  * Returns bytes read on success; 0 on EOF; less than zero on error
 232  */
 233 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 234                         struct inode *ecryptfs_inode)
 235 {
 236         struct file *lower_file;
 237         lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
 238         if (!lower_file)
 239                 return -EIO;
 240         return kernel_read(lower_file, offset, data, size);
 241 }
 242
 243 /**
 244  * ecryptfs_read_lower_page_segment
 245  * @page_for_ecryptfs: The page into which data for eCryptfs will be
 246  *                     written
 247  * @offset_in_page: Offset in @page_for_ecryptfs from which to start
 248  *                  writing
 249  * @size: The number of bytes to write into @page_for_ecryptfs
 250  * @ecryptfs_inode: The eCryptfs inode
 251  *
 252  * Determines the byte offset in the file for the given page and
 253  * offset within the page, maps the page, and makes the call to read
 254  * the contents of @page_for_ecryptfs from the lower inode.
 255  *
 256  * Returns zero on success; non-zero otherwise
 257  */
 258 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
 259                                      pgoff_t page_index,
 260                                      size_t offset_in_page, size_t size,
 261                                      struct inode *ecryptfs_inode)
 262 {
 263         char *virt;
 264         loff_t offset;
 265         int rc;
 266
 267         offset = ((((loff_t)page_index) << PAGE_SHIFT) + offset_in_page);
 268         virt = kmap(page_for_ecryptfs);
 269         rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
 270         if (rc > 0)
 271                 rc = 0;
 272         kunmap(page_for_ecryptfs);
 273         flush_dcache_page(page_for_ecryptfs);
 274         return rc;
 275 }