libntfs-3g/mst.c

   1 /**
   2  * mst.c - Multi sector fixup handling code. Originated from the Linux-NTFS project.
   3  *
   4  * Copyright (c) 2000-2004 Anton Altaparmakov
   5  * Copyright (c) 2006-2009 Szabolcs Szakacsits
   6  *
   7  * This program/include file is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as published
   9  * by the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program/include file is distributed in the hope that it will be
  13  * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  14  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU 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 (in the main directory of the NTFS-3G
  19  * distribution in the file COPYING); if not, write to the Free Software
  20  * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21  */
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include "config.h"
  25 #endif
  26
  27 #ifdef HAVE_ERRNO_H
  28 #include <errno.h>
  29 #endif
  30
  31 #include "mst.h"
  32 #include "logging.h"
  33
  34 /*
  35  * Basic validation of a NTFS multi-sector record.  The record size must be a
  36  * multiple of the logical sector size; and the update sequence array must be
  37  * properly aligned, of the expected length, and must end before the last le16
  38  * in the first logical sector.
  39  */
  40 static BOOL
  41 is_valid_record(u32 size, u16 usa_ofs, u16 usa_count)
  42 {
  43         return size % NTFS_BLOCK_SIZE == 0 &&
  44                 usa_ofs % 2 == 0 &&
  45                 usa_count == 1 + (size / NTFS_BLOCK_SIZE) &&
  46                 usa_ofs + ((u32)usa_count * 2) <= NTFS_BLOCK_SIZE - 2;
  47 }
  48
  49 /**
  50  * ntfs_mst_post_read_fixup - deprotect multi sector transfer protected data
  51  * @b:          pointer to the data to deprotect
  52  * @size:       size in bytes of @b
  53  *
  54  * Perform the necessary post read multi sector transfer fixups and detect the
  55  * presence of incomplete multi sector transfers. - In that case, overwrite the
  56  * magic of the ntfs record header being processed with "BAAD" (in memory only!)
  57  * and abort processing.
  58  *
  59  * Return 0 on success and -1 on error, with errno set to the error code. The
  60  * following error codes are defined:
  61  *      EINVAL  Invalid arguments or invalid NTFS record in buffer @b.
  62  *      EIO     Multi sector transfer error was detected. Magic of the NTFS
  63  *              record in @b will have been set to "BAAD".
  64  */
  65 int ntfs_mst_post_read_fixup_warn(NTFS_RECORD *b, const u32 size,
  66                                         BOOL warn)
  67 {
  68         u16 usa_ofs, usa_count, usn;
  69         u16 *usa_pos, *data_pos;
  70
  71         ntfs_log_trace("Entering\n");
  72
  73         /* Setup the variables. */
  74         usa_ofs = le16_to_cpu(b->usa_ofs);
  75         usa_count = le16_to_cpu(b->usa_count);
  76
  77         if (!is_valid_record(size, usa_ofs, usa_count)) {
  78                 errno = EINVAL;
  79                 if (warn) {
  80                         ntfs_log_perror("%s: magic: 0x%08lx  size: %ld "
  81                                         "  usa_ofs: %d  usa_count: %u",
  82                                          __FUNCTION__,
  83                                         (long)le32_to_cpu(*(le32 *)b),
  84                                         (long)size, (int)usa_ofs,
  85                                         (unsigned int)usa_count);
  86                 }
  87                 return -1;
  88         }
  89         /* Position of usn in update sequence array. */
  90         usa_pos = (u16*)b + usa_ofs/sizeof(u16);
  91         /*
  92          * The update sequence number which has to be equal to each of the
  93          * u16 values before they are fixed up. Note no need to care for
  94          * endianness since we are comparing and moving data for on disk
  95          * structures which means the data is consistent. - If it is
  96          * consistency the wrong endianness it doesn't make any difference.
  97          */
  98         usn = *usa_pos;
  99         /*
 100          * Position in protected data of first u16 that needs fixing up.
 101          */
 102         data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
 103         /*
 104          * Check for incomplete multi sector transfer(s).
 105          */
 106         while (--usa_count) {
 107                 if (*data_pos != usn) {
 108                         /*
 109                          * Incomplete multi sector transfer detected! )-:
 110                          * Set the magic to "BAAD" and return failure.
 111                          * Note that magic_BAAD is already converted to le32.
 112                          */
 113                         errno = EIO;
 114                         ntfs_log_perror("Incomplete multi-sector transfer: "
 115                                 "magic: 0x%08x  size: %d  usa_ofs: %d  usa_count:"
 116                                 " %d  data: %d  usn: %d", le32_to_cpu(*(le32 *)b), size,
 117                                 usa_ofs, usa_count, *data_pos, usn);
 118                         b->magic = magic_BAAD;
 119                         return -1;
 120                 }
 121                 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
 122         }
 123         /* Re-setup the variables. */
 124         usa_count = le16_to_cpu(b->usa_count);
 125         data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
 126         /* Fixup all sectors. */
 127         while (--usa_count) {
 128                 /*
 129                  * Increment position in usa and restore original data from
 130                  * the usa into the data buffer.
 131                  */
 132                 *data_pos = *(++usa_pos);
 133                 /* Increment position in data as well. */
 134                 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
 135         }
 136         return 0;
 137 }
 138
 139 /*
 140  *              Deprotect multi sector transfer protected data
 141  *      with a warning if an error is found.
 142  */
 143
 144 int ntfs_mst_post_read_fixup(NTFS_RECORD *b, const u32 size)
 145 {
 146         return (ntfs_mst_post_read_fixup_warn(b,size,TRUE));
 147 }
 148
 149 /**
 150  * ntfs_mst_pre_write_fixup - apply multi sector transfer protection
 151  * @b:          pointer to the data to protect
 152  * @size:       size in bytes of @b
 153  *
 154  * Perform the necessary pre write multi sector transfer fixup on the data
 155  * pointer to by @b of @size.
 156  *
 157  * Return 0 if fixups applied successfully or -1 if no fixups were performed
 158  * due to errors. In that case errno i set to the error code (EINVAL).
 159  *
 160  * NOTE: We consider the absence / invalidity of an update sequence array to
 161  * mean error. This means that you have to create a valid update sequence
 162  * array header in the ntfs record before calling this function, otherwise it
 163  * will fail (the header needs to contain the position of the update sequence
 164  * array together with the number of elements in the array). You also need to
 165  * initialise the update sequence number before calling this function
 166  * otherwise a random word will be used (whatever was in the record at that
 167  * position at that time).
 168  */
 169 int ntfs_mst_pre_write_fixup(NTFS_RECORD *b, const u32 size)
 170 {
 171         u16 usa_ofs, usa_count, usn;
 172         le16 le_usn;
 173         le16 *usa_pos, *data_pos;
 174
 175         ntfs_log_trace("Entering\n");
 176
 177         /* Sanity check + only fixup if it makes sense. */
 178         if (!b || ntfs_is_baad_record(b->magic) ||
 179                         ntfs_is_hole_record(b->magic)) {
 180                 errno = EINVAL;
 181                 ntfs_log_perror("%s: bad argument", __FUNCTION__);
 182                 return -1;
 183         }
 184         /* Setup the variables. */
 185         usa_ofs = le16_to_cpu(b->usa_ofs);
 186         usa_count = le16_to_cpu(b->usa_count);
 187
 188         if (!is_valid_record(size, usa_ofs, usa_count)) {
 189                 errno = EINVAL;
 190                 ntfs_log_perror("%s", __FUNCTION__);
 191                 return -1;
 192         }
 193         /* Position of usn in update sequence array. */
 194         usa_pos = (le16*)((u8*)b + usa_ofs);
 195         /*
 196          * Cyclically increment the update sequence number
 197          * (skipping 0 and -1, i.e. 0xffff).
 198          */
 199         usn = le16_to_cpup(usa_pos) + 1;
 200         if (usn == 0xffff || !usn)
 201                 usn = 1;
 202         le_usn = cpu_to_le16(usn);
 203         *usa_pos = le_usn;
 204         /* Position in data of first le16 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 the position in the usa and save the
 210                  * original data from the data buffer into the usa.
 211                  */
 212                 *(++usa_pos) = *data_pos;
 213                 /* Apply fixup to data. */
 214                 *data_pos = le_usn;
 215                 /* Increment position in data as well. */
 216                 data_pos += NTFS_BLOCK_SIZE/sizeof(le16);
 217         }
 218         return 0;
 219 }
 220
 221 /**
 222  * ntfs_mst_post_write_fixup - deprotect multi sector transfer protected data
 223  * @b:          pointer to the data to deprotect
 224  *
 225  * Perform the necessary post write multi sector transfer fixup, not checking
 226  * for any errors, because we assume we have just used
 227  * ntfs_mst_pre_write_fixup(), thus the data will be fine or we would never
 228  * have gotten here.
 229  */
 230 void ntfs_mst_post_write_fixup(NTFS_RECORD *b)
 231 {
 232         u16 *usa_pos, *data_pos;
 233
 234         u16 usa_ofs = le16_to_cpu(b->usa_ofs);
 235         u16 usa_count = le16_to_cpu(b->usa_count);
 236
 237         ntfs_log_trace("Entering\n");
 238
 239         /* Position of usn in update sequence array. */
 240         usa_pos = (u16*)b + usa_ofs/sizeof(u16);
 241
 242         /* Position in protected data of first u16 that needs fixing up. */
 243         data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
 244
 245         /* Fixup all sectors. */
 246         while (--usa_count) {
 247                 /*
 248                  * Increment position in usa and restore original data from
 249                  * the usa into the data buffer.
 250                  */
 251                 *data_pos = *(++usa_pos);
 252
 253                 /* Increment position in data as well. */
 254                 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
 255         }
 256 }
 257