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f86c4403ed
The validation contained an off-by-one error. The expression '(u32)(usa_ofs + (usa_count * 2)) > size' used 'usa_count' after it had been decremented to skip the update sequence number entry. Consequently, the code could read out of bounds, up to two bytes past the end of the MST-protected record. Furthermore, as documented in the comment in layout.h for "NTFS_RECORD" and also on MSDN for "MULTI_SECTOR_HEADER", the update sequence array must end before the last le16 in the first logical sector --- not merely before the end of the record. Fix the validation and move it into a helper function, as it was done identically in the read and write paths. Signed-off-by: Eric Biggers <ebiggers3@gmail.com>
258 lines
8.0 KiB
C
258 lines
8.0 KiB
C
/**
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* mst.c - Multi sector fixup handling code. Originated from the Linux-NTFS project.
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*
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* Copyright (c) 2000-2004 Anton Altaparmakov
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* Copyright (c) 2006-2009 Szabolcs Szakacsits
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*
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* This program/include file is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as published
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* by the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program/include file is distributed in the hope that it will be
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* useful, but WITHOUT ANY WARRANTY; without even the implied warranty
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* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (in the main directory of the NTFS-3G
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* distribution in the file COPYING); if not, write to the Free Software
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* Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#ifdef HAVE_ERRNO_H
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#include <errno.h>
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#endif
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#include "mst.h"
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#include "logging.h"
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/*
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* Basic validation of a NTFS multi-sector record. The record size must be a
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* multiple of the logical sector size; and the update sequence array must be
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* properly aligned, of the expected length, and must end before the last le16
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* in the first logical sector.
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*/
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static BOOL
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is_valid_record(u32 size, u16 usa_ofs, u16 usa_count)
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{
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return size % NTFS_BLOCK_SIZE == 0 &&
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usa_ofs % 2 == 0 &&
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usa_count == 1 + (size / NTFS_BLOCK_SIZE) &&
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usa_ofs + ((u32)usa_count * 2) <= NTFS_BLOCK_SIZE - 2;
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}
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/**
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* ntfs_mst_post_read_fixup - deprotect multi sector transfer protected data
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* @b: pointer to the data to deprotect
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* @size: size in bytes of @b
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*
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* Perform the necessary post read multi sector transfer fixups and detect the
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* presence of incomplete multi sector transfers. - In that case, overwrite the
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* magic of the ntfs record header being processed with "BAAD" (in memory only!)
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* and abort processing.
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*
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* Return 0 on success and -1 on error, with errno set to the error code. The
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* following error codes are defined:
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* EINVAL Invalid arguments or invalid NTFS record in buffer @b.
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* EIO Multi sector transfer error was detected. Magic of the NTFS
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* record in @b will have been set to "BAAD".
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*/
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int ntfs_mst_post_read_fixup_warn(NTFS_RECORD *b, const u32 size,
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BOOL warn)
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{
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u16 usa_ofs, usa_count, usn;
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u16 *usa_pos, *data_pos;
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ntfs_log_trace("Entering\n");
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/* Setup the variables. */
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usa_ofs = le16_to_cpu(b->usa_ofs);
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usa_count = le16_to_cpu(b->usa_count);
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if (!is_valid_record(size, usa_ofs, usa_count)) {
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errno = EINVAL;
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if (warn) {
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ntfs_log_perror("%s: magic: 0x%08lx size: %ld "
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" usa_ofs: %d usa_count: %u",
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__FUNCTION__,
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(long)le32_to_cpu(*(le32 *)b),
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(long)size, (int)usa_ofs,
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(unsigned int)usa_count);
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}
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return -1;
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}
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/* Position of usn in update sequence array. */
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usa_pos = (u16*)b + usa_ofs/sizeof(u16);
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/*
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* The update sequence number which has to be equal to each of the
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* u16 values before they are fixed up. Note no need to care for
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* endianness since we are comparing and moving data for on disk
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* structures which means the data is consistent. - If it is
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* consistency the wrong endianness it doesn't make any difference.
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*/
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usn = *usa_pos;
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/*
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* Position in protected data of first u16 that needs fixing up.
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*/
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data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
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/*
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* Check for incomplete multi sector transfer(s).
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*/
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while (--usa_count) {
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if (*data_pos != usn) {
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/*
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* Incomplete multi sector transfer detected! )-:
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* Set the magic to "BAAD" and return failure.
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* Note that magic_BAAD is already converted to le32.
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*/
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errno = EIO;
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ntfs_log_perror("Incomplete multi-sector transfer: "
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"magic: 0x%08x size: %d usa_ofs: %d usa_count:"
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" %d data: %d usn: %d", le32_to_cpu(*(le32 *)b), size,
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usa_ofs, usa_count, *data_pos, usn);
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b->magic = magic_BAAD;
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return -1;
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}
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data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
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}
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/* Re-setup the variables. */
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usa_count = le16_to_cpu(b->usa_count);
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data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
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/* Fixup all sectors. */
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while (--usa_count) {
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/*
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* Increment position in usa and restore original data from
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* the usa into the data buffer.
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*/
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*data_pos = *(++usa_pos);
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/* Increment position in data as well. */
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data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
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}
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return 0;
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}
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/*
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* Deprotect multi sector transfer protected data
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* with a warning if an error is found.
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*/
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int ntfs_mst_post_read_fixup(NTFS_RECORD *b, const u32 size)
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{
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return (ntfs_mst_post_read_fixup_warn(b,size,TRUE));
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}
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/**
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* ntfs_mst_pre_write_fixup - apply multi sector transfer protection
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* @b: pointer to the data to protect
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* @size: size in bytes of @b
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*
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* Perform the necessary pre write multi sector transfer fixup on the data
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* pointer to by @b of @size.
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*
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* Return 0 if fixups applied successfully or -1 if no fixups were performed
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* due to errors. In that case errno i set to the error code (EINVAL).
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*
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* NOTE: We consider the absence / invalidity of an update sequence array to
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* mean error. This means that you have to create a valid update sequence
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* array header in the ntfs record before calling this function, otherwise it
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* will fail (the header needs to contain the position of the update sequence
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* array together with the number of elements in the array). You also need to
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* initialise the update sequence number before calling this function
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* otherwise a random word will be used (whatever was in the record at that
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* position at that time).
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*/
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int ntfs_mst_pre_write_fixup(NTFS_RECORD *b, const u32 size)
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{
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u16 usa_ofs, usa_count, usn;
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le16 le_usn;
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le16 *usa_pos, *data_pos;
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ntfs_log_trace("Entering\n");
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/* Sanity check + only fixup if it makes sense. */
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if (!b || ntfs_is_baad_record(b->magic) ||
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ntfs_is_hole_record(b->magic)) {
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errno = EINVAL;
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ntfs_log_perror("%s: bad argument", __FUNCTION__);
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return -1;
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}
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/* Setup the variables. */
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usa_ofs = le16_to_cpu(b->usa_ofs);
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usa_count = le16_to_cpu(b->usa_count);
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if (!is_valid_record(size, usa_ofs, usa_count)) {
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errno = EINVAL;
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ntfs_log_perror("%s", __FUNCTION__);
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return -1;
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}
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/* Position of usn in update sequence array. */
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usa_pos = (le16*)((u8*)b + usa_ofs);
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/*
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* Cyclically increment the update sequence number
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* (skipping 0 and -1, i.e. 0xffff).
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*/
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usn = le16_to_cpup(usa_pos) + 1;
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if (usn == 0xffff || !usn)
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usn = 1;
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le_usn = cpu_to_le16(usn);
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*usa_pos = le_usn;
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/* Position in data of first le16 that needs fixing up. */
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data_pos = (le16*)b + NTFS_BLOCK_SIZE/sizeof(le16) - 1;
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/* Fixup all sectors. */
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while (--usa_count) {
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/*
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* Increment the position in the usa and save the
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* original data from the data buffer into the usa.
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*/
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*(++usa_pos) = *data_pos;
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/* Apply fixup to data. */
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*data_pos = le_usn;
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/* Increment position in data as well. */
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data_pos += NTFS_BLOCK_SIZE/sizeof(le16);
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}
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return 0;
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}
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/**
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* ntfs_mst_post_write_fixup - deprotect multi sector transfer protected data
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* @b: pointer to the data to deprotect
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*
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* Perform the necessary post write multi sector transfer fixup, not checking
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* for any errors, because we assume we have just used
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* ntfs_mst_pre_write_fixup(), thus the data will be fine or we would never
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* have gotten here.
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*/
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void ntfs_mst_post_write_fixup(NTFS_RECORD *b)
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{
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u16 *usa_pos, *data_pos;
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u16 usa_ofs = le16_to_cpu(b->usa_ofs);
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u16 usa_count = le16_to_cpu(b->usa_count);
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ntfs_log_trace("Entering\n");
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/* Position of usn in update sequence array. */
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usa_pos = (u16*)b + usa_ofs/sizeof(u16);
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/* Position in protected data of first u16 that needs fixing up. */
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data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
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/* Fixup all sectors. */
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while (--usa_count) {
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/*
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* Increment position in usa and restore original data from
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* the usa into the data buffer.
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*/
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*data_pos = *(++usa_pos);
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/* Increment position in data as well. */
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data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
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}
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}
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