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 zero on success; non-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 ecryptfs_inode_info *inode_info; 43 ssize_t octets_written; 44 mm_segment_t fs_save; 45 int rc = 0; 46 47 inode_info = ecryptfs_inode_to_private(ecryptfs_inode); 48 mutex_lock(&inode_info->lower_file_mutex); 49 BUG_ON(!inode_info->lower_file); 50 inode_info->lower_file->f_pos = offset; 51 fs_save = get_fs(); 52 set_fs(get_ds()); 53 octets_written = vfs_write(inode_info->lower_file, data, size, 54 &inode_info->lower_file->f_pos); 55 set_fs(fs_save); 56 if (octets_written < 0) { 57 printk(KERN_ERR "%s: octets_written = [%td]; " 58 "expected [%td]\n", __func__, octets_written, size); 59 rc = -EINVAL; 60 } 61 mutex_unlock(&inode_info->lower_file_mutex); 62 mark_inode_dirty_sync(ecryptfs_inode); 63 return rc; 64 } 65 66 /** 67 * ecryptfs_write_lower_page_segment 68 * @ecryptfs_inode: The eCryptfs inode 69 * @page_for_lower: The page containing the data to be written to the 70 * lower file 71 * @offset_in_page: The offset in the @page_for_lower from which to 72 * start writing the data 73 * @size: The amount of data from @page_for_lower to write to the 74 * lower file 75 * 76 * Determines the byte offset in the file for the given page and 77 * offset within the page, maps the page, and makes the call to write 78 * the contents of @page_for_lower to the lower inode. 79 * 80 * Returns zero on success; non-zero otherwise 81 */ 82 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode, 83 struct page *page_for_lower, 84 size_t offset_in_page, size_t size) 85 { 86 char *virt; 87 loff_t offset; 88 int rc; 89 90 offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT) 91 + offset_in_page); 92 virt = kmap(page_for_lower); 93 rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size); 94 kunmap(page_for_lower); 95 return rc; 96 } 97 98 /** 99 * ecryptfs_write 100 * @ecryptfs_file: The eCryptfs file into which to write 101 * @data: Virtual address where data to write is located 102 * @offset: Offset in the eCryptfs file at which to begin writing the 103 * data from @data 104 * @size: The number of bytes to write from @data 105 * 106 * Write an arbitrary amount of data to an arbitrary location in the 107 * eCryptfs inode page cache. This is done on a page-by-page, and then 108 * by an extent-by-extent, basis; individual extents are encrypted and 109 * written to the lower page cache (via VFS writes). This function 110 * takes care of all the address translation to locations in the lower 111 * filesystem; it also handles truncate events, writing out zeros 112 * where necessary. 113 * 114 * Returns zero on success; non-zero otherwise 115 */ 116 int ecryptfs_write(struct file *ecryptfs_file, char *data, loff_t offset, 117 size_t size) 118 { 119 struct page *ecryptfs_page; 120 struct ecryptfs_crypt_stat *crypt_stat; 121 struct inode *ecryptfs_inode = ecryptfs_file->f_dentry->d_inode; 122 char *ecryptfs_page_virt; 123 loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode); 124 loff_t data_offset = 0; 125 loff_t pos; 126 int rc = 0; 127 128 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 129 /* 130 * if we are writing beyond current size, then start pos 131 * at the current size - we'll fill in zeros from there. 132 */ 133 if (offset > ecryptfs_file_size) 134 pos = ecryptfs_file_size; 135 else 136 pos = offset; 137 while (pos < (offset + size)) { 138 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT); 139 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK); 140 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page); 141 size_t total_remaining_bytes = ((offset + size) - pos); 142 143 if (num_bytes > total_remaining_bytes) 144 num_bytes = total_remaining_bytes; 145 if (pos < offset) { 146 /* remaining zeros to write, up to destination offset */ 147 size_t total_remaining_zeros = (offset - pos); 148 149 if (num_bytes > total_remaining_zeros) 150 num_bytes = total_remaining_zeros; 151 } 152 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file, 153 ecryptfs_page_idx); 154 if (IS_ERR(ecryptfs_page)) { 155 rc = PTR_ERR(ecryptfs_page); 156 printk(KERN_ERR "%s: Error getting page at " 157 "index [%ld] from eCryptfs inode " 158 "mapping; rc = [%d]\n", __func__, 159 ecryptfs_page_idx, rc); 160 goto out; 161 } 162 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0); 163 164 /* 165 * pos: where we're now writing, offset: where the request was 166 * If current pos is before request, we are filling zeros 167 * If we are at or beyond request, we are writing the *data* 168 * If we're in a fresh page beyond eof, zero it in either case 169 */ 170 if (pos < offset || !start_offset_in_page) { 171 /* We are extending past the previous end of the file. 172 * Fill in zero values to the end of the page */ 173 memset(((char *)ecryptfs_page_virt 174 + start_offset_in_page), 0, 175 PAGE_CACHE_SIZE - start_offset_in_page); 176 } 177 178 /* pos >= offset, we are now writing the data request */ 179 if (pos >= offset) { 180 memcpy(((char *)ecryptfs_page_virt 181 + start_offset_in_page), 182 (data + data_offset), num_bytes); 183 data_offset += num_bytes; 184 } 185 kunmap_atomic(ecryptfs_page_virt, KM_USER0); 186 flush_dcache_page(ecryptfs_page); 187 SetPageUptodate(ecryptfs_page); 188 unlock_page(ecryptfs_page); 189 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) 190 rc = ecryptfs_encrypt_page(ecryptfs_page); 191 else 192 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, 193 ecryptfs_page, 194 start_offset_in_page, 195 data_offset); 196 page_cache_release(ecryptfs_page); 197 if (rc) { 198 printk(KERN_ERR "%s: Error encrypting " 199 "page; rc = [%d]\n", __func__, rc); 200 goto out; 201 } 202 pos += num_bytes; 203 } 204 if ((offset + size) > ecryptfs_file_size) { 205 i_size_write(ecryptfs_inode, (offset + size)); 206 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) { 207 rc = ecryptfs_write_inode_size_to_metadata( 208 ecryptfs_inode); 209 if (rc) { 210 printk(KERN_ERR "Problem with " 211 "ecryptfs_write_inode_size_to_metadata; " 212 "rc = [%d]\n", rc); 213 goto out; 214 } 215 } 216 } 217 out: 218 return rc; 219 } 220 221 /** 222 * ecryptfs_read_lower 223 * @data: The read data is stored here by this function 224 * @offset: Byte offset in the lower file from which to read the data 225 * @size: Number of bytes to read from @offset of the lower file and 226 * store into @data 227 * @ecryptfs_inode: The eCryptfs inode 228 * 229 * Read @size bytes of data at byte offset @offset from the lower 230 * inode into memory location @data. 231 * 232 * Returns zero on success; non-zero on error 233 */ 234 int ecryptfs_read_lower(char *data, loff_t offset, size_t size, 235 struct inode *ecryptfs_inode) 236 { 237 struct ecryptfs_inode_info *inode_info = 238 ecryptfs_inode_to_private(ecryptfs_inode); 239 ssize_t octets_read; 240 mm_segment_t fs_save; 241 int rc = 0; 242 243 mutex_lock(&inode_info->lower_file_mutex); 244 BUG_ON(!inode_info->lower_file); 245 inode_info->lower_file->f_pos = offset; 246 fs_save = get_fs(); 247 set_fs(get_ds()); 248 octets_read = vfs_read(inode_info->lower_file, data, size, 249 &inode_info->lower_file->f_pos); 250 set_fs(fs_save); 251 if (octets_read < 0) { 252 printk(KERN_ERR "%s: octets_read = [%td]; " 253 "expected [%td]\n", __func__, octets_read, size); 254 rc = -EINVAL; 255 } 256 mutex_unlock(&inode_info->lower_file_mutex); 257 return rc; 258 } 259 260 /** 261 * ecryptfs_read_lower_page_segment 262 * @page_for_ecryptfs: The page into which data for eCryptfs will be 263 * written 264 * @offset_in_page: Offset in @page_for_ecryptfs from which to start 265 * writing 266 * @size: The number of bytes to write into @page_for_ecryptfs 267 * @ecryptfs_inode: The eCryptfs inode 268 * 269 * Determines the byte offset in the file for the given page and 270 * offset within the page, maps the page, and makes the call to read 271 * the contents of @page_for_ecryptfs from the lower inode. 272 * 273 * Returns zero on success; non-zero otherwise 274 */ 275 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs, 276 pgoff_t page_index, 277 size_t offset_in_page, size_t size, 278 struct inode *ecryptfs_inode) 279 { 280 char *virt; 281 loff_t offset; 282 int rc; 283 284 offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page); 285 virt = kmap(page_for_ecryptfs); 286 rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode); 287 kunmap(page_for_ecryptfs); 288 flush_dcache_page(page_for_ecryptfs); 289 return rc; 290 } 291 292 #if 0 293 /** 294 * ecryptfs_read 295 * @data: The virtual address into which to write the data read (and 296 * possibly decrypted) from the lower file 297 * @offset: The offset in the decrypted view of the file from which to 298 * read into @data 299 * @size: The number of bytes to read into @data 300 * @ecryptfs_file: The eCryptfs file from which to read 301 * 302 * Read an arbitrary amount of data from an arbitrary location in the 303 * eCryptfs page cache. This is done on an extent-by-extent basis; 304 * individual extents are decrypted and read from the lower page 305 * cache (via VFS reads). This function takes care of all the 306 * address translation to locations in the lower filesystem. 307 * 308 * Returns zero on success; non-zero otherwise 309 */ 310 int ecryptfs_read(char *data, loff_t offset, size_t size, 311 struct file *ecryptfs_file) 312 { 313 struct page *ecryptfs_page; 314 char *ecryptfs_page_virt; 315 loff_t ecryptfs_file_size = 316 i_size_read(ecryptfs_file->f_dentry->d_inode); 317 loff_t data_offset = 0; 318 loff_t pos; 319 int rc = 0; 320 321 if ((offset + size) > ecryptfs_file_size) { 322 rc = -EINVAL; 323 printk(KERN_ERR "%s: Attempt to read data past the end of the " 324 "file; offset = [%lld]; size = [%td]; " 325 "ecryptfs_file_size = [%lld]\n", 326 __func__, offset, size, ecryptfs_file_size); 327 goto out; 328 } 329 pos = offset; 330 while (pos < (offset + size)) { 331 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT); 332 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK); 333 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page); 334 size_t total_remaining_bytes = ((offset + size) - pos); 335 336 if (num_bytes > total_remaining_bytes) 337 num_bytes = total_remaining_bytes; 338 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file, 339 ecryptfs_page_idx); 340 if (IS_ERR(ecryptfs_page)) { 341 rc = PTR_ERR(ecryptfs_page); 342 printk(KERN_ERR "%s: Error getting page at " 343 "index [%ld] from eCryptfs inode " 344 "mapping; rc = [%d]\n", __func__, 345 ecryptfs_page_idx, rc); 346 goto out; 347 } 348 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0); 349 memcpy((data + data_offset), 350 ((char *)ecryptfs_page_virt + start_offset_in_page), 351 num_bytes); 352 kunmap_atomic(ecryptfs_page_virt, KM_USER0); 353 flush_dcache_page(ecryptfs_page); 354 SetPageUptodate(ecryptfs_page); 355 unlock_page(ecryptfs_page); 356 page_cache_release(ecryptfs_page); 357 pos += num_bytes; 358 data_offset += num_bytes; 359 } 360 out: 361 return rc; 362 } 363 #endif /* 0 */ 364