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