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 loff_t total_remaining_bytes = ((offset + size) - pos); 134 135 if (fatal_signal_pending(current)) { 136 rc = -EINTR; 137 break; 138 } 139 140 if (num_bytes > total_remaining_bytes) 141 num_bytes = total_remaining_bytes; 142 if (pos < offset) { 143 /* remaining zeros to write, up to destination offset */ 144 loff_t total_remaining_zeros = (offset - pos); 145 146 if (num_bytes > total_remaining_zeros) 147 num_bytes = total_remaining_zeros; 148 } 149 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode, 150 ecryptfs_page_idx); 151 if (IS_ERR(ecryptfs_page)) { 152 rc = PTR_ERR(ecryptfs_page); 153 printk(KERN_ERR "%s: Error getting page at " 154 "index [%ld] from eCryptfs inode " 155 "mapping; rc = [%d]\n", __func__, 156 ecryptfs_page_idx, rc); 157 goto out; 158 } 159 ecryptfs_page_virt = kmap_atomic(ecryptfs_page); 160 161 /* 162 * pos: where we're now writing, offset: where the request was 163 * If current pos is before request, we are filling zeros 164 * If we are at or beyond request, we are writing the *data* 165 * If we're in a fresh page beyond eof, zero it in either case 166 */ 167 if (pos < offset || !start_offset_in_page) { 168 /* We are extending past the previous end of the file. 169 * Fill in zero values to the end of the page */ 170 memset(((char *)ecryptfs_page_virt 171 + start_offset_in_page), 0, 172 PAGE_CACHE_SIZE - start_offset_in_page); 173 } 174 175 /* pos >= offset, we are now writing the data request */ 176 if (pos >= offset) { 177 memcpy(((char *)ecryptfs_page_virt 178 + start_offset_in_page), 179 (data + data_offset), num_bytes); 180 data_offset += num_bytes; 181 } 182 kunmap_atomic(ecryptfs_page_virt); 183 flush_dcache_page(ecryptfs_page); 184 SetPageUptodate(ecryptfs_page); 185 unlock_page(ecryptfs_page); 186 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) 187 rc = ecryptfs_encrypt_page(ecryptfs_page); 188 else 189 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, 190 ecryptfs_page, 191 start_offset_in_page, 192 data_offset); 193 page_cache_release(ecryptfs_page); 194 if (rc) { 195 printk(KERN_ERR "%s: Error encrypting " 196 "page; rc = [%d]\n", __func__, rc); 197 goto out; 198 } 199 pos += num_bytes; 200 } 201 if (pos > ecryptfs_file_size) { 202 i_size_write(ecryptfs_inode, pos); 203 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) { 204 int rc2; 205 206 rc2 = ecryptfs_write_inode_size_to_metadata( 207 ecryptfs_inode); 208 if (rc2) { 209 printk(KERN_ERR "Problem with " 210 "ecryptfs_write_inode_size_to_metadata; " 211 "rc = [%d]\n", rc2); 212 if (!rc) 213 rc = rc2; 214 goto out; 215 } 216 } 217 } 218 out: 219 return rc; 220 } 221 222 /** 223 * ecryptfs_read_lower 224 * @data: The read data is stored here by this function 225 * @offset: Byte offset in the lower file from which to read the data 226 * @size: Number of bytes to read from @offset of the lower file and 227 * store into @data 228 * @ecryptfs_inode: The eCryptfs inode 229 * 230 * Read @size bytes of data at byte offset @offset from the lower 231 * inode into memory location @data. 232 * 233 * Returns bytes read on success; 0 on EOF; less than zero on error 234 */ 235 int ecryptfs_read_lower(char *data, loff_t offset, size_t size, 236 struct inode *ecryptfs_inode) 237 { 238 struct file *lower_file; 239 mm_segment_t fs_save; 240 ssize_t rc; 241 242 lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file; 243 if (!lower_file) 244 return -EIO; 245 fs_save = get_fs(); 246 set_fs(get_ds()); 247 rc = vfs_read(lower_file, data, size, &offset); 248 set_fs(fs_save); 249 return rc; 250 } 251 252 /** 253 * ecryptfs_read_lower_page_segment 254 * @page_for_ecryptfs: The page into which data for eCryptfs will be 255 * written 256 * @offset_in_page: Offset in @page_for_ecryptfs from which to start 257 * writing 258 * @size: The number of bytes to write into @page_for_ecryptfs 259 * @ecryptfs_inode: The eCryptfs inode 260 * 261 * Determines the byte offset in the file for the given page and 262 * offset within the page, maps the page, and makes the call to read 263 * the contents of @page_for_ecryptfs from the lower inode. 264 * 265 * Returns zero on success; non-zero otherwise 266 */ 267 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs, 268 pgoff_t page_index, 269 size_t offset_in_page, size_t size, 270 struct inode *ecryptfs_inode) 271 { 272 char *virt; 273 loff_t offset; 274 int rc; 275 276 offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page); 277 virt = kmap(page_for_ecryptfs); 278 rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode); 279 if (rc > 0) 280 rc = 0; 281 kunmap(page_for_ecryptfs); 282 flush_dcache_page(page_for_ecryptfs); 283 return rc; 284 } 285