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         mm_segment_t fs_save;
  44         ssize_t rc;
  45
  46         lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
  47         if (!lower_file)
  48                 return -EIO;
  49         fs_save = get_fs();
  50         set_fs(get_ds());
  51         rc = vfs_write(lower_file, data, size, &offset);
  52         set_fs(fs_save);
  53         mark_inode_dirty_sync(ecryptfs_inode);
  54         return rc;
  55 }
  56
  57 /**
  58  * ecryptfs_write_lower_page_segment
  59  * @ecryptfs_inode: The eCryptfs inode
  60  * @page_for_lower: The page containing the data to be written to the
  61  *                  lower file
  62  * @offset_in_page: The offset in the @page_for_lower from which to
  63  *                  start writing the data
  64  * @size: The amount of data from @page_for_lower to write to the
  65  *        lower file
  66  *
  67  * Determines the byte offset in the file for the given page and
  68  * offset within the page, maps the page, and makes the call to write
  69  * the contents of @page_for_lower to the lower inode.
  70  *
  71  * Returns zero on success; non-zero otherwise
  72  */
  73 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
  74                                       struct page *page_for_lower,
  75                                       size_t offset_in_page, size_t size)
  76 {
  77         char *virt;
  78         loff_t offset;
  79         int rc;
  80
  81         offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
  82                   + offset_in_page);
  83         virt = kmap(page_for_lower);
  84         rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
  85         if (rc > 0)
  86                 rc = 0;
  87         kunmap(page_for_lower);
  88         return rc;
  89 }
  90
  91 /**
  92  * ecryptfs_write
  93  * @ecryptfs_inode: The eCryptfs file into which to write
  94  * @data: Virtual address where data to write is located
  95  * @offset: Offset in the eCryptfs file at which to begin writing the
  96  *          data from @data
  97  * @size: The number of bytes to write from @data
  98  *
  99  * Write an arbitrary amount of data to an arbitrary location in the
 100  * eCryptfs inode page cache. This is done on a page-by-page, and then
 101  * by an extent-by-extent, basis; individual extents are encrypted and
 102  * written to the lower page cache (via VFS writes). This function
 103  * takes care of all the address translation to locations in the lower
 104  * filesystem; it also handles truncate events, writing out zeros
 105  * where necessary.
 106  *
 107  * Returns zero on success; non-zero otherwise
 108  */
 109 int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
 110                    size_t size)
 111 {
 112         struct page *ecryptfs_page;
 113         struct ecryptfs_crypt_stat *crypt_stat;
 114         char *ecryptfs_page_virt;
 115         loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
 116         loff_t data_offset = 0;
 117         loff_t pos;
 118         int rc = 0;
 119
 120         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 121         /*
 122          * if we are writing beyond current size, then start pos
 123          * at the current size - we'll fill in zeros from there.
 124          */
 125         if (offset > ecryptfs_file_size)
 126                 pos = ecryptfs_file_size;
 127         else
 128                 pos = offset;
 129         while (pos < (offset + size)) {
 130                 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 131                 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 132                 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 133                 loff_t total_remaining_bytes = ((offset + size) - pos);
 134
 135                 if (fatal_signal_pending(current)) {
 136                         rc = -EINTR;
 137                         break;
 138                 }
 139
 140                 if (num_bytes > total_remaining_bytes)
 141                         num_bytes = total_remaining_bytes;
 142                 if (pos < offset) {
 143                         /* remaining zeros to write, up to destination offset */
 144                         loff_t total_remaining_zeros = (offset - pos);
 145
 146                         if (num_bytes > total_remaining_zeros)
 147                                 num_bytes = total_remaining_zeros;
 148                 }
 149                 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
 150                                                          ecryptfs_page_idx);
 151                 if (IS_ERR(ecryptfs_page)) {
 152                         rc = PTR_ERR(ecryptfs_page);
 153                         printk(KERN_ERR "%s: Error getting page at "
 154                                "index [%ld] from eCryptfs inode "
 155                                "mapping; rc = [%d]\n", __func__,
 156                                ecryptfs_page_idx, rc);
 157                         goto out;
 158                 }
 159                 ecryptfs_page_virt = kmap_atomic(ecryptfs_page);
 160
 161                 /*
 162                  * pos: where we're now writing, offset: where the request was
 163                  * If current pos is before request, we are filling zeros
 164                  * If we are at or beyond request, we are writing the *data*
 165                  * If we're in a fresh page beyond eof, zero it in either case
 166                  */
 167                 if (pos < offset || !start_offset_in_page) {
 168                         /* We are extending past the previous end of the file.
 169                          * Fill in zero values to the end of the page */
 170                         memset(((char *)ecryptfs_page_virt
 171                                 + start_offset_in_page), 0,
 172                                 PAGE_CACHE_SIZE - start_offset_in_page);
 173                 }
 174
 175                 /* pos >= offset, we are now writing the data request */
 176                 if (pos >= offset) {
 177                         memcpy(((char *)ecryptfs_page_virt
 178                                 + start_offset_in_page),
 179                                (data + data_offset), num_bytes);
 180                         data_offset += num_bytes;
 181                 }
 182                 kunmap_atomic(ecryptfs_page_virt);
 183                 flush_dcache_page(ecryptfs_page);
 184                 SetPageUptodate(ecryptfs_page);
 185                 unlock_page(ecryptfs_page);
 186                 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 187                         rc = ecryptfs_encrypt_page(ecryptfs_page);
 188                 else
 189                         rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
 190                                                 ecryptfs_page,
 191                                                 start_offset_in_page,
 192                                                 data_offset);
 193                 page_cache_release(ecryptfs_page);
 194                 if (rc) {
 195                         printk(KERN_ERR "%s: Error encrypting "
 196                                "page; rc = [%d]\n", __func__, rc);
 197                         goto out;
 198                 }
 199                 pos += num_bytes;
 200         }
 201         if (pos > ecryptfs_file_size) {
 202                 i_size_write(ecryptfs_inode, pos);
 203                 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
 204                         int rc2;
 205
 206                         rc2 = ecryptfs_write_inode_size_to_metadata(
 207                                                                 ecryptfs_inode);
 208                         if (rc2) {
 209                                 printk(KERN_ERR "Problem with "
 210                                        "ecryptfs_write_inode_size_to_metadata; "
 211                                        "rc = [%d]\n", rc2);
 212                                 if (!rc)
 213                                         rc = rc2;
 214                                 goto out;
 215                         }
 216                 }
 217         }
 218 out:
 219         return rc;
 220 }
 221
 222 /**
 223  * ecryptfs_read_lower
 224  * @data: The read data is stored here by this function
 225  * @offset: Byte offset in the lower file from which to read the data
 226  * @size: Number of bytes to read from @offset of the lower file and
 227  *        store into @data
 228  * @ecryptfs_inode: The eCryptfs inode
 229  *
 230  * Read @size bytes of data at byte offset @offset from the lower
 231  * inode into memory location @data.
 232  *
 233  * Returns bytes read on success; 0 on EOF; less than zero on error
 234  */
 235 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 236                         struct inode *ecryptfs_inode)
 237 {
 238         struct file *lower_file;
 239         mm_segment_t fs_save;
 240         ssize_t rc;
 241
 242         lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
 243         if (!lower_file)
 244                 return -EIO;
 245         fs_save = get_fs();
 246         set_fs(get_ds());
 247         rc = vfs_read(lower_file, data, size, &offset);
 248         set_fs(fs_save);
 249         return rc;
 250 }
 251
 252 /**
 253  * ecryptfs_read_lower_page_segment
 254  * @page_for_ecryptfs: The page into which data for eCryptfs will be
 255  *                     written
 256  * @offset_in_page: Offset in @page_for_ecryptfs from which to start
 257  *                  writing
 258  * @size: The number of bytes to write into @page_for_ecryptfs
 259  * @ecryptfs_inode: The eCryptfs inode
 260  *
 261  * Determines the byte offset in the file for the given page and
 262  * offset within the page, maps the page, and makes the call to read
 263  * the contents of @page_for_ecryptfs from the lower inode.
 264  *
 265  * Returns zero on success; non-zero otherwise
 266  */
 267 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
 268                                      pgoff_t page_index,
 269                                      size_t offset_in_page, size_t size,
 270                                      struct inode *ecryptfs_inode)
 271 {
 272         char *virt;
 273         loff_t offset;
 274         int rc;
 275
 276         offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
 277         virt = kmap(page_for_ecryptfs);
 278         rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
 279         if (rc > 0)
 280                 rc = 0;
 281         kunmap(page_for_ecryptfs);
 282         flush_dcache_page(page_for_ecryptfs);
 283         return rc;
 284 }