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_file: 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 file *ecryptfs_file, char *data, loff_t offset, 113 size_t size) 114 { 115 struct page *ecryptfs_page; 116 struct ecryptfs_crypt_stat *crypt_stat; 117 struct inode *ecryptfs_inode = ecryptfs_file->f_dentry->d_inode; 118 char *ecryptfs_page_virt; 119 loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode); 120 loff_t data_offset = 0; 121 loff_t pos; 122 int rc = 0; 123 124 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 125 /* 126 * if we are writing beyond current size, then start pos 127 * at the current size - we'll fill in zeros from there. 128 */ 129 if (offset > ecryptfs_file_size) 130 pos = ecryptfs_file_size; 131 else 132 pos = offset; 133 while (pos < (offset + size)) { 134 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT); 135 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK); 136 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page); 137 size_t total_remaining_bytes = ((offset + size) - pos); 138 139 if (num_bytes > total_remaining_bytes) 140 num_bytes = total_remaining_bytes; 141 if (pos < offset) { 142 /* remaining zeros to write, up to destination offset */ 143 size_t total_remaining_zeros = (offset - pos); 144 145 if (num_bytes > total_remaining_zeros) 146 num_bytes = total_remaining_zeros; 147 } 148 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file, 149 ecryptfs_page_idx); 150 if (IS_ERR(ecryptfs_page)) { 151 rc = PTR_ERR(ecryptfs_page); 152 printk(KERN_ERR "%s: Error getting page at " 153 "index [%ld] from eCryptfs inode " 154 "mapping; rc = [%d]\n", __func__, 155 ecryptfs_page_idx, rc); 156 goto out; 157 } 158 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0); 159 160 /* 161 * pos: where we're now writing, offset: where the request was 162 * If current pos is before request, we are filling zeros 163 * If we are at or beyond request, we are writing the *data* 164 * If we're in a fresh page beyond eof, zero it in either case 165 */ 166 if (pos < offset || !start_offset_in_page) { 167 /* We are extending past the previous end of the file. 168 * Fill in zero values to the end of the page */ 169 memset(((char *)ecryptfs_page_virt 170 + start_offset_in_page), 0, 171 PAGE_CACHE_SIZE - start_offset_in_page); 172 } 173 174 /* pos >= offset, we are now writing the data request */ 175 if (pos >= offset) { 176 memcpy(((char *)ecryptfs_page_virt 177 + start_offset_in_page), 178 (data + data_offset), num_bytes); 179 data_offset += num_bytes; 180 } 181 kunmap_atomic(ecryptfs_page_virt, KM_USER0); 182 flush_dcache_page(ecryptfs_page); 183 SetPageUptodate(ecryptfs_page); 184 unlock_page(ecryptfs_page); 185 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) 186 rc = ecryptfs_encrypt_page(ecryptfs_page); 187 else 188 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, 189 ecryptfs_page, 190 start_offset_in_page, 191 data_offset); 192 page_cache_release(ecryptfs_page); 193 if (rc) { 194 printk(KERN_ERR "%s: Error encrypting " 195 "page; rc = [%d]\n", __func__, rc); 196 goto out; 197 } 198 pos += num_bytes; 199 } 200 if ((offset + size) > ecryptfs_file_size) { 201 i_size_write(ecryptfs_inode, (offset + size)); 202 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) { 203 rc = ecryptfs_write_inode_size_to_metadata( 204 ecryptfs_inode); 205 if (rc) { 206 printk(KERN_ERR "Problem with " 207 "ecryptfs_write_inode_size_to_metadata; " 208 "rc = [%d]\n", rc); 209 goto out; 210 } 211 } 212 } 213 out: 214 return rc; 215 } 216 217 /** 218 * ecryptfs_read_lower 219 * @data: The read data is stored here by this function 220 * @offset: Byte offset in the lower file from which to read the data 221 * @size: Number of bytes to read from @offset of the lower file and 222 * store into @data 223 * @ecryptfs_inode: The eCryptfs inode 224 * 225 * Read @size bytes of data at byte offset @offset from the lower 226 * inode into memory location @data. 227 * 228 * Returns bytes read on success; 0 on EOF; less than zero on error 229 */ 230 int ecryptfs_read_lower(char *data, loff_t offset, size_t size, 231 struct inode *ecryptfs_inode) 232 { 233 struct ecryptfs_inode_info *inode_info = 234 ecryptfs_inode_to_private(ecryptfs_inode); 235 mm_segment_t fs_save; 236 ssize_t rc; 237 238 mutex_lock(&inode_info->lower_file_mutex); 239 BUG_ON(!inode_info->lower_file); 240 inode_info->lower_file->f_pos = offset; 241 fs_save = get_fs(); 242 set_fs(get_ds()); 243 rc = vfs_read(inode_info->lower_file, data, size, 244 &inode_info->lower_file->f_pos); 245 set_fs(fs_save); 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 if (rc > 0) 278 rc = 0; 279 kunmap(page_for_ecryptfs); 280 flush_dcache_page(page_for_ecryptfs); 281 return rc; 282 } 283 284 #if 0 285 /** 286 * ecryptfs_read 287 * @data: The virtual address into which to write the data read (and 288 * possibly decrypted) from the lower file 289 * @offset: The offset in the decrypted view of the file from which to 290 * read into @data 291 * @size: The number of bytes to read into @data 292 * @ecryptfs_file: The eCryptfs file from which to read 293 * 294 * Read an arbitrary amount of data from an arbitrary location in the 295 * eCryptfs page cache. This is done on an extent-by-extent basis; 296 * individual extents are decrypted and read from the lower page 297 * cache (via VFS reads). This function takes care of all the 298 * address translation to locations in the lower filesystem. 299 * 300 * Returns zero on success; non-zero otherwise 301 */ 302 int ecryptfs_read(char *data, loff_t offset, size_t size, 303 struct file *ecryptfs_file) 304 { 305 struct page *ecryptfs_page; 306 char *ecryptfs_page_virt; 307 loff_t ecryptfs_file_size = 308 i_size_read(ecryptfs_file->f_dentry->d_inode); 309 loff_t data_offset = 0; 310 loff_t pos; 311 int rc = 0; 312 313 if ((offset + size) > ecryptfs_file_size) { 314 rc = -EINVAL; 315 printk(KERN_ERR "%s: Attempt to read data past the end of the " 316 "file; offset = [%lld]; size = [%td]; " 317 "ecryptfs_file_size = [%lld]\n", 318 __func__, offset, size, ecryptfs_file_size); 319 goto out; 320 } 321 pos = offset; 322 while (pos < (offset + size)) { 323 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT); 324 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK); 325 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page); 326 size_t total_remaining_bytes = ((offset + size) - pos); 327 328 if (num_bytes > total_remaining_bytes) 329 num_bytes = total_remaining_bytes; 330 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file, 331 ecryptfs_page_idx); 332 if (IS_ERR(ecryptfs_page)) { 333 rc = PTR_ERR(ecryptfs_page); 334 printk(KERN_ERR "%s: Error getting page at " 335 "index [%ld] from eCryptfs inode " 336 "mapping; rc = [%d]\n", __func__, 337 ecryptfs_page_idx, rc); 338 goto out; 339 } 340 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0); 341 memcpy((data + data_offset), 342 ((char *)ecryptfs_page_virt + start_offset_in_page), 343 num_bytes); 344 kunmap_atomic(ecryptfs_page_virt, KM_USER0); 345 flush_dcache_page(ecryptfs_page); 346 SetPageUptodate(ecryptfs_page); 347 unlock_page(ecryptfs_page); 348 page_cache_release(ecryptfs_page); 349 pos += num_bytes; 350 data_offset += num_bytes; 351 } 352 out: 353 return rc; 354 } 355 #endif /* 0 */ 356