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