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