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 ssize_t rc; 44 45 lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file; 46 if (!lower_file) 47 return -EIO; 48 rc = kernel_write(lower_file, data, size, offset); 49 mark_inode_dirty_sync(ecryptfs_inode); 50 return rc; 51 } 52 53 /** 54 * ecryptfs_write_lower_page_segment 55 * @ecryptfs_inode: The eCryptfs inode 56 * @page_for_lower: The page containing the data to be written to the 57 * lower file 58 * @offset_in_page: The offset in the @page_for_lower from which to 59 * start writing the data 60 * @size: The amount of data from @page_for_lower to write to the 61 * lower file 62 * 63 * Determines the byte offset in the file for the given page and 64 * offset within the page, maps the page, and makes the call to write 65 * the contents of @page_for_lower to the lower inode. 66 * 67 * Returns zero on success; non-zero otherwise 68 */ 69 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode, 70 struct page *page_for_lower, 71 size_t offset_in_page, size_t size) 72 { 73 char *virt; 74 loff_t offset; 75 int rc; 76 77 offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT) 78 + offset_in_page); 79 virt = kmap(page_for_lower); 80 rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size); 81 if (rc > 0) 82 rc = 0; 83 kunmap(page_for_lower); 84 return rc; 85 } 86 87 /** 88 * ecryptfs_write 89 * @ecryptfs_inode: The eCryptfs file into which to write 90 * @data: Virtual address where data to write is located 91 * @offset: Offset in the eCryptfs file at which to begin writing the 92 * data from @data 93 * @size: The number of bytes to write from @data 94 * 95 * Write an arbitrary amount of data to an arbitrary location in the 96 * eCryptfs inode page cache. This is done on a page-by-page, and then 97 * by an extent-by-extent, basis; individual extents are encrypted and 98 * written to the lower page cache (via VFS writes). This function 99 * takes care of all the address translation to locations in the lower 100 * filesystem; it also handles truncate events, writing out zeros 101 * where necessary. 102 * 103 * Returns zero on success; non-zero otherwise 104 */ 105 int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset, 106 size_t size) 107 { 108 struct page *ecryptfs_page; 109 struct ecryptfs_crypt_stat *crypt_stat; 110 char *ecryptfs_page_virt; 111 loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode); 112 loff_t data_offset = 0; 113 loff_t pos; 114 int rc = 0; 115 116 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; 117 /* 118 * if we are writing beyond current size, then start pos 119 * at the current size - we'll fill in zeros from there. 120 */ 121 if (offset > ecryptfs_file_size) 122 pos = ecryptfs_file_size; 123 else 124 pos = offset; 125 while (pos < (offset + size)) { 126 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT); 127 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK); 128 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page); 129 loff_t total_remaining_bytes = ((offset + size) - pos); 130 131 if (fatal_signal_pending(current)) { 132 rc = -EINTR; 133 break; 134 } 135 136 if (num_bytes > total_remaining_bytes) 137 num_bytes = total_remaining_bytes; 138 if (pos < offset) { 139 /* remaining zeros to write, up to destination offset */ 140 loff_t total_remaining_zeros = (offset - pos); 141 142 if (num_bytes > total_remaining_zeros) 143 num_bytes = total_remaining_zeros; 144 } 145 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode, 146 ecryptfs_page_idx); 147 if (IS_ERR(ecryptfs_page)) { 148 rc = PTR_ERR(ecryptfs_page); 149 printk(KERN_ERR "%s: Error getting page at " 150 "index [%ld] from eCryptfs inode " 151 "mapping; rc = [%d]\n", __func__, 152 ecryptfs_page_idx, rc); 153 goto out; 154 } 155 ecryptfs_page_virt = kmap_atomic(ecryptfs_page); 156 157 /* 158 * pos: where we're now writing, offset: where the request was 159 * If current pos is before request, we are filling zeros 160 * If we are at or beyond request, we are writing the *data* 161 * If we're in a fresh page beyond eof, zero it in either case 162 */ 163 if (pos < offset || !start_offset_in_page) { 164 /* We are extending past the previous end of the file. 165 * Fill in zero values to the end of the page */ 166 memset(((char *)ecryptfs_page_virt 167 + start_offset_in_page), 0, 168 PAGE_CACHE_SIZE - start_offset_in_page); 169 } 170 171 /* pos >= offset, we are now writing the data request */ 172 if (pos >= offset) { 173 memcpy(((char *)ecryptfs_page_virt 174 + start_offset_in_page), 175 (data + data_offset), num_bytes); 176 data_offset += num_bytes; 177 } 178 kunmap_atomic(ecryptfs_page_virt); 179 flush_dcache_page(ecryptfs_page); 180 SetPageUptodate(ecryptfs_page); 181 unlock_page(ecryptfs_page); 182 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) 183 rc = ecryptfs_encrypt_page(ecryptfs_page); 184 else 185 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, 186 ecryptfs_page, 187 start_offset_in_page, 188 data_offset); 189 page_cache_release(ecryptfs_page); 190 if (rc) { 191 printk(KERN_ERR "%s: Error encrypting " 192 "page; rc = [%d]\n", __func__, rc); 193 goto out; 194 } 195 pos += num_bytes; 196 } 197 if (pos > ecryptfs_file_size) { 198 i_size_write(ecryptfs_inode, pos); 199 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) { 200 int rc2; 201 202 rc2 = ecryptfs_write_inode_size_to_metadata( 203 ecryptfs_inode); 204 if (rc2) { 205 printk(KERN_ERR "Problem with " 206 "ecryptfs_write_inode_size_to_metadata; " 207 "rc = [%d]\n", rc2); 208 if (!rc) 209 rc = rc2; 210 goto out; 211 } 212 } 213 } 214 out: 215 return rc; 216 } 217 218 /** 219 * ecryptfs_read_lower 220 * @data: The read data is stored here by this function 221 * @offset: Byte offset in the lower file from which to read the data 222 * @size: Number of bytes to read from @offset of the lower file and 223 * store into @data 224 * @ecryptfs_inode: The eCryptfs inode 225 * 226 * Read @size bytes of data at byte offset @offset from the lower 227 * inode into memory location @data. 228 * 229 * Returns bytes read on success; 0 on EOF; less than zero on error 230 */ 231 int ecryptfs_read_lower(char *data, loff_t offset, size_t size, 232 struct inode *ecryptfs_inode) 233 { 234 struct file *lower_file; 235 mm_segment_t fs_save; 236 ssize_t rc; 237 238 lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file; 239 if (!lower_file) 240 return -EIO; 241 fs_save = get_fs(); 242 set_fs(get_ds()); 243 rc = vfs_read(lower_file, data, size, &offset); 244 set_fs(fs_save); 245 return rc; 246 } 247 248 /** 249 * ecryptfs_read_lower_page_segment 250 * @page_for_ecryptfs: The page into which data for eCryptfs will be 251 * written 252 * @offset_in_page: Offset in @page_for_ecryptfs from which to start 253 * writing 254 * @size: The number of bytes to write into @page_for_ecryptfs 255 * @ecryptfs_inode: The eCryptfs inode 256 * 257 * Determines the byte offset in the file for the given page and 258 * offset within the page, maps the page, and makes the call to read 259 * the contents of @page_for_ecryptfs from the lower inode. 260 * 261 * Returns zero on success; non-zero otherwise 262 */ 263 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs, 264 pgoff_t page_index, 265 size_t offset_in_page, size_t size, 266 struct inode *ecryptfs_inode) 267 { 268 char *virt; 269 loff_t offset; 270 int rc; 271 272 offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page); 273 virt = kmap(page_for_ecryptfs); 274 rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode); 275 if (rc > 0) 276 rc = 0; 277 kunmap(page_for_ecryptfs); 278 flush_dcache_page(page_for_ecryptfs); 279 return rc; 280 } 281