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