1/* 2 * ntfs_mst.c - NTFS kernel multi sector transfer protection operations. 3 * 4 * Copyright (c) 2006-2008 Anton Altaparmakov. All Rights Reserved. 5 * Portions Copyright (c) 2006-2008 Apple Inc. All Rights Reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions are met: 9 * 10 * 1. Redistributions of source code must retain the above copyright notice, 11 * this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright notice, 13 * this list of conditions and the following disclaimer in the documentation 14 * and/or other materials provided with the distribution. 15 * 3. Neither the name of Apple Inc. ("Apple") nor the names of its 16 * contributors may be used to endorse or promote products derived from this 17 * software without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY 20 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 21 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 22 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY 23 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 24 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 25 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 26 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 * 30 * ALTERNATIVELY, provided that this notice and licensing terms are retained in 31 * full, this file may be redistributed and/or modified under the terms of the 32 * GNU General Public License (GPL) Version 2, in which case the provisions of 33 * that version of the GPL will apply to you instead of the license terms 34 * above. You can obtain a copy of the GPL Version 2 at 35 * http://developer.apple.com/opensource/licenses/gpl-2.txt. 36 */ 37 38#include <sys/errno.h> 39 40#include "ntfs.h" 41#include "ntfs_endian.h" 42#include "ntfs_layout.h" 43#include "ntfs_mst.h" 44#include "ntfs_types.h" 45 46/** 47 * ntfs_mst_fixup_post_read - deprotect multi sector transfer protected data 48 * @b: pointer to the data to deprotect 49 * @size: size in bytes of @b 50 * 51 * Perform the necessary post read multi sector transfer fixup and detect the 52 * presence of incomplete multi sector transfers. 53 * 54 * In the case of an incomplete transfer being detected, overwrite the magic of 55 * the ntfs record header being processed with "BAAD" and abort processing. 56 * 57 * Return 0 on success and EIO on error ("BAAD" magic will be present). 58 * 59 * NOTE: We consider the absence / invalidity of an update sequence array to 60 * mean that the structure is not protected at all and hence does not need to 61 * be fixed up. Thus, we return success and not failure in this case. This is 62 * in contrast to ntfs_mst_fixup_pre_write(), see below. 63 */ 64errno_t ntfs_mst_fixup_post_read(NTFS_RECORD *b, const u32 size) 65{ 66 u16 *usa_pos, *data_pos; 67 u16 usa_ofs, usa_count, usn; 68 69 /* Setup the variables. */ 70 usa_ofs = le16_to_cpu(b->usa_ofs); 71 /* Decrement usa_count to get number of fixups. */ 72 usa_count = le16_to_cpu(b->usa_count) - 1; 73 /* Size and alignment checks. */ 74 if (size & (NTFS_BLOCK_SIZE - 1) || usa_ofs & 1 || 75 (u32)usa_ofs + ((u32)usa_count * 2) > size || 76 (size >> NTFS_BLOCK_SIZE_SHIFT) != usa_count) 77 return 0; 78 /* Position of usn in update sequence array. */ 79 usa_pos = (u16*)b + usa_ofs/sizeof(u16); 80 /* 81 * The update sequence number which has to be equal to each of the u16 82 * values before they are fixed up. Note no need to care for 83 * endianness since we are comparing and moving data for on disk 84 * structures which means the data is consistent. If it is consistenty 85 * the wrong endianness it does not make any difference. 86 */ 87 usn = *usa_pos; 88 /* Position in protected data of first u16 that needs fixing up. */ 89 data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1; 90 /* Check for incomplete multi sector transfer(s). */ 91 while (usa_count--) { 92 if (*data_pos != usn) { 93 /* 94 * Incomplete multi sector transfer detected! )-: 95 * Set the magic to "BAAD" and return failure. 96 * Note that magic_BAAD is already little endian. 97 */ 98 b->magic = magic_BAAD; 99 return EIO; 100 } 101 data_pos += NTFS_BLOCK_SIZE/sizeof(u16); 102 } 103 /* Re-setup the variables. */ 104 usa_count = le16_to_cpu(b->usa_count) - 1; 105 data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1; 106 /* Fixup all sectors. */ 107 while (usa_count--) { 108 /* 109 * Increment position in usa and restore original data from 110 * the usa into the data buffer. 111 */ 112 *data_pos = *(++usa_pos); 113 /* Increment position in data as well. */ 114 data_pos += NTFS_BLOCK_SIZE/sizeof(u16); 115 } 116 return 0; 117} 118 119/** 120 * ntfs_mst_fixup_pre_write - apply multi sector transfer protection 121 * @b: pointer to the data to protect 122 * @size: size in bytes of @b 123 * 124 * Perform the necessary pre write multi sector transfer fixup on the data 125 * pointed to by @b of @size. 126 * 127 * Return 0 if fixup applied (success) or EINVAL if no fixup was performed 128 * (assumed not needed). This is in contrast to ntfs_mst_fixup_post_read() 129 * above. 130 * 131 * NOTE: We consider the absence / invalidity of an update sequence array to 132 * mean that the structure is not subject to protection and hence does not need 133 * to be fixed up. This means that you have to create a valid update sequence 134 * array header in the ntfs record before calling this function, otherwise it 135 * will fail (the header needs to contain the position of the update sequence 136 * array together with the number of elements in the array). You also need to 137 * initialise the update sequence number before calling this function 138 * otherwise a random word will be used (whatever was in the record at that 139 * position at that time). 140 */ 141errno_t ntfs_mst_fixup_pre_write(NTFS_RECORD *b, const u32 size) 142{ 143 le16 *usa_pos, *data_pos; 144 u16 usa_ofs, usa_count, usn; 145 le16 le_usn; 146 147 /* Sanity check + only fixup if it makes sense. */ 148 if (!b || ntfs_is_baad_record(b->magic) || 149 ntfs_is_hole_record(b->magic)) 150 return EINVAL; 151 /* Setup the variables. */ 152 usa_ofs = le16_to_cpu(b->usa_ofs); 153 /* Decrement usa_count to get number of fixups. */ 154 usa_count = le16_to_cpu(b->usa_count) - 1; 155 /* Size and alignment checks. */ 156 if (size & (NTFS_BLOCK_SIZE - 1) || usa_ofs & 1 || 157 (u32)usa_ofs + ((u32)usa_count * 2) > size || 158 (size >> NTFS_BLOCK_SIZE_SHIFT) != usa_count) 159 return EINVAL; 160 /* Position of usn in update sequence array. */ 161 usa_pos = (le16*)((u8*)b + usa_ofs); 162 /* 163 * Cyclically increment the update sequence number (skipping 0 and -1, 164 * i.e. 0xffff). 165 */ 166 usn = le16_to_cpup(usa_pos) + 1; 167 if (usn == 0xffff || !usn) 168 usn = 1; 169 le_usn = cpu_to_le16(usn); 170 *usa_pos = le_usn; 171 /* Position in data of first u16 that needs fixing up. */ 172 data_pos = (le16*)b + NTFS_BLOCK_SIZE/sizeof(le16) - 1; 173 /* Fixup all sectors. */ 174 while (usa_count--) { 175 /* 176 * Increment the position in the usa and save the 177 * original data from the data buffer into the usa. 178 */ 179 *(++usa_pos) = *data_pos; 180 /* Apply fixup to data. */ 181 *data_pos = le_usn; 182 /* Increment position in data as well. */ 183 data_pos += NTFS_BLOCK_SIZE/sizeof(le16); 184 } 185 return 0; 186} 187 188/** 189 * ntfs_mst_fixup_post_write - fast deprotect mst protected data 190 * @b: pointer to the data to deprotect 191 * 192 * Perform the necessary post write multi sector transfer fixup, not checking 193 * for any errors, because we assume we have just successfully used 194 * ntfs_mst_fixup_pre_write(), thus the data will be fine or we would never 195 * have gotten here. 196 */ 197void ntfs_mst_fixup_post_write(NTFS_RECORD *b) 198{ 199 le16 *usa_pos, *data_pos; 200 u16 usa_ofs = le16_to_cpu(b->usa_ofs); 201 u16 usa_count = le16_to_cpu(b->usa_count) - 1; 202 /* Position of usn in update sequence array. */ 203 usa_pos = (le16*)b + usa_ofs/sizeof(le16); 204 /* Position in protected data of first u16 that needs fixing up. */ 205 data_pos = (le16*)b + NTFS_BLOCK_SIZE/sizeof(le16) - 1; 206 /* Fixup all sectors. */ 207 while (usa_count--) { 208 /* 209 * Increment position in usa and restore original data from 210 * the usa into the data buffer. 211 */ 212 *data_pos = *(++usa_pos); 213 /* Increment position in data as well. */ 214 data_pos += NTFS_BLOCK_SIZE/sizeof(le16); 215 } 216} 217