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- Fix a bug where we would not always detect that we have reached the 

end of a compression block because we were ending at minus one byte
  which is effectively the same as being at the end.  The fix is to
  check whether the uncompressed buffer has been fully filled and if so
  we assume we have reached the end of the compression block.  A big
  thank you to Marcin Gibuła for the bug report, the assistance in
  tracking down the bug and testing the fix.
- Fix a bug where we forgot to reset the data_size and initialized_size
  in two error code paths.
- Fix a bug where an uncompressed block could be misdetected as a
  compressed one if it was made up of multiple runs.

(Logical change 1.390)
edge.strict_endians
cantab.net!aia21 2004-05-11 09:21:24 +00:00
parent 0649be9d8e
commit da742f48da
1 changed files with 66 additions and 10 deletions
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76
libntfs/compress.c
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@ -1,5 +1,5 @@
/*
* compress.c - Compressed attribute handling code. Part of the Linux-NTFS
* compress.c - Compressed attribute handling code. Part of the Linux-NTFS
* project.
*
* Copyright (c) 2004 Anton Altaparmakov
@ -88,8 +88,13 @@ static int ntfs_decompress(u8 *dest, const u32 dest_size,
do_next_sb:
Dprintf("Beginning sub-block at offset = 0x%x in the cb.\n",
cb - cb_start);
/* Have we reached the end of the compression block? */
if (cb == cb_end || !le16_to_cpup((u16*)cb)) {
/*
* Have we reached the end of the compression block or the end of the
* decompressed data? The latter can happen for example if the current
* position in the compression block is one byte before its end so the
* first two checks do not detect it.
*/
if (cb == cb_end || !le16_to_cpup((u16*)cb) || dest == dest_end) {
Dprintf("Completed. Returning success (0).\n");
return 0;
}
@ -166,7 +171,7 @@ do_next_tag:
/* Continue with the next token. */
continue;
}
/*
/*
* We have a phrase token. Make sure it is not the first tag in
* the sb as this is illegal and would confuse the code below.
*/
@ -229,6 +234,53 @@ return_overflow:
return -1;
}
/**
* ntfs_is_cb_compressed - internal function, do not use
*
* This is a very specialised function determining if a cb is compressed or
* uncompressed. It is assumed that checking for a sparse cb has already been
* performed and that the cb is not sparse. It makes all sorts of other
* assumptions as well and hence it is not useful anywhere other than where it
* is used at the moment. Please, do not make this function available for use
* outside of compress.c as it is bound to confuse people and not do what they
* want.
*
* Return TRUE on errors so that the error will be detected later on in the
* code. Might be a bit confusing to debug but there really should never be
* errors coming from here.
*/
static __inline__ BOOL ntfs_is_cb_compressed(ntfs_attr *na,
runlist_element *rl, VCN cb_start_vcn, int cb_clusters)
{
/*
* The simplest case: the run starting at @cb_start_vcn contains
* @cb_clusters clusters which are all not sparse, thus the cb is not
* compressed.
*/
if (rl->length - (cb_start_vcn - rl->vcn) >= cb_clusters)
return FALSE;
cb_clusters -= rl->length - (cb_start_vcn - rl->vcn);
do {
/* Go to the next run. */
rl++;
/* Map the next runlist fragment if it is not mapped. */
if (rl->lcn < LCN_HOLE || !rl->length) {
rl = ntfs_attr_find_vcn(na, rl->vcn);
if (!rl || rl->lcn < LCN_HOLE || !rl->length)
return TRUE;
}
/* If the current run is sparse, the cb is compressed. */
if (rl->lcn == LCN_HOLE)
return TRUE;
/* If the whole cb is not sparse, it is not compressed. */
if (rl->length >= cb_clusters)
return FALSE;
cb_clusters -= rl->length;
} while (cb_clusters > 0);
/* All cb_clusters were not sparse thus the cb is not compressed. */
return FALSE;
}
/**
* ntfs_compressed_attr_pread - read from a compressed attribute
* @na: ntfs attribute to read from
@ -361,7 +413,7 @@ do_next_cb:
total += to_read;
count -= to_read;
b = (u8*)b + to_read;
} else if (rl->length - (vcn - rl->vcn) >= cb_clusters) {
} else if (!ntfs_is_cb_compressed(na, rl, vcn, cb_clusters)) {
s64 tdata_size, tinitialized_size;
/*
* Uncompressed cb, read it straight into the destination range
@ -372,8 +424,8 @@ do_next_cb:
* Read the uncompressed data into the destination buffer.
* NOTE: We cheat a little bit here by marking the attribute as
* not compressed in the ntfs_attr structure so that we can
* read the data by simply using ntfs_attr_pread(). (-8 Note,
* Note, we have to modify data_size and initialized_size
* read the data by simply using ntfs_attr_pread(). (-8
* NOTE: we have to modify data_size and initialized_size
* temporarily as well...
*/
to_read = min(count, cb_size - ofs);
@ -386,6 +438,8 @@ do_next_cb:
br = ntfs_attr_pread(na, ofs, to_read, b);
if (br < 0) {
err = errno;
na->data_size = tdata_size;
na->initialized_size = tinitialized_size;
NAttrSetCompressed(na);
free(cb);
free(dest);
@ -417,8 +471,9 @@ do_next_cb:
* NOTE: We cheat a little bit here by marking the attribute as
* not compressed in the ntfs_attr structure so that we can
* read the raw, compressed data by simply using
* ntfs_attr_pread(). (-8 Note, we have to modify data_size
* and initialized_size temporarily as well...
* ntfs_attr_pread(). (-8
* NOTE: We have to modify data_size and initialized_size
* temporarily as well...
*/
to_read = cb_size;
NAttrClearCompressed(na);
@ -431,6 +486,8 @@ do_next_cb:
(cb_pos - cb), to_read, cb_pos);
if (br < 0) {
err = errno;
na->data_size = tdata_size;
na->initialized_size = tinitialized_size;
NAttrSetCompressed(na);
free(cb);
free(dest);
@ -474,4 +531,3 @@ do_next_cb:
/* Return number of bytes read. */
return total + total2;
}