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