linux/fs/ecryptfs/read_write.c
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   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 */
  39int 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 */
  69int 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_CACHE_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 */
 105int 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_CACHE_SHIFT);
 127                size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 128                size_t num_bytes = (PAGE_CACHE_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_CACHE_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                page_cache_release(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        }
 214out:
 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 */
 231int 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 */
 256int 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_CACHE_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}
 274
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