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avoid corruption risk with write-in-same-location logic

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This commit is contained in:
Frank Warmerdam 2007-11-02 19:57:28 +00:00
parent e770990619
commit d14dae9c0c
2 changed files with 49 additions and 50 deletions
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10
ChangeLog
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@ -1,5 +1,15 @@
2007-11-02 Frank Warmerdam <warmerdam@pobox.com>
* tif_write.c: Rip out the fancy logic in TIFFAppendToStrip() for
establishing if an existing tile can be rewritten to the same location
by comparing the current size to all the other blocks in the same
directory. This is dangerous in many situations and can easily
corrupt a file. (observed in esoteric GDAL situation that's hard to
document). This change involves leaving the stripbytecount[] values
unaltered till TIFFAppendToStrip(). Now we only write a block back
to the same location it used to be at if the new data is the same
size or smaller - otherwise we move it to the end of file.
* tif_dirwrite.c: Try to avoid writing out a full readbuffer of tile
data when writing the directory just because we have BEENWRITING at
some point in the past. This was causing odd junk to be written out

89
libtiff/tif_write.c
View File

@ -1,4 +1,4 @@
/* $Id: tif_write.c,v 1.29 2007-10-01 12:43:50 joris Exp $ */
/* $Id: tif_write.c,v 1.30 2007-11-02 19:57:28 fwarmerdam Exp $ */
/*
* Copyright (c) 1988-1997 Sam Leffler
@ -227,10 +227,8 @@ TIFFWriteEncodedStrip(TIFF* tif, uint32 strip, void* data, tmsize_t cc)
if( td->td_stripbytecount[strip] > 0 )
{
/* if we are writing over existing tiles, zero length. */
td->td_stripbytecount[strip] = 0;
/* this forces TIFFAppendToStrip() to do a seek */
/* Force TIFFAppendToStrip() to consider placing data at end
of file. */
tif->tif_curoff = 0;
}
@ -362,10 +360,8 @@ TIFFWriteEncodedTile(TIFF* tif, uint32 tile, void* data, tmsize_t cc)
if( td->td_stripbytecount[tile] > 0 )
{
/* if we are writing over existing tiles, zero length. */
td->td_stripbytecount[tile] = 0;
/* this forces TIFFAppendToStrip() to do a seek */
/* Force TIFFAppendToStrip() to consider placing data at end
of file. */
tif->tif_curoff = 0;
}
@ -634,48 +630,41 @@ TIFFAppendToStrip(TIFF* tif, uint32 strip, uint8* data, tmsize_t cc)
uint64 m;
if (td->td_stripoffset[strip] == 0 || tif->tif_curoff == 0) {
/*
* No current offset, set the current strip.
*/
assert(td->td_nstrips > 0);
if (td->td_stripoffset[strip] != 0) {
/*
* Prevent overlapping of the data chunks. We need
* this to enable in place updating of the compressed
* images. Larger blocks will be moved at the end of
* the file without any optimization of the spare
* space, so such scheme is not too much effective.
*/
if (td->td_stripbytecountsorted) {
if (strip == td->td_nstrips - 1
|| td->td_stripoffset[strip + 1] <
td->td_stripoffset[strip] + cc) {
td->td_stripoffset[strip] =
TIFFSeekFile(tif,0, SEEK_END);
td->td_stripbytecountsorted = 0;
}
} else {
uint32 i;
for (i = 0; i < td->td_nstrips; i++) {
if (td->td_stripoffset[i] >
td->td_stripoffset[strip]
&& td->td_stripoffset[i] <
td->td_stripoffset[strip] + cc) {
td->td_stripoffset[strip] =
TIFFSeekFile(tif, 0, SEEK_END);
}
}
}
assert(td->td_nstrips > 0);
if (!SeekOK(tif, td->td_stripoffset[strip])) {
TIFFErrorExt(tif->tif_clientdata, module,
"Seek error at scanline %lu",
(unsigned long)tif->tif_row);
return (0);
}
} else
td->td_stripoffset[strip] = TIFFSeekFile(tif, 0, SEEK_END);
tif->tif_curoff = td->td_stripoffset[strip];
if( td->td_stripbytecount[strip] != 0
&& td->td_stripoffset[strip] != 0
&& td->td_stripbytecount[strip] >= (uint64) cc )
{
/*
* There is already tile data on disk, and the new tile
* data we have to will fit in the same space. The only
* aspect of this that is risky is that there could be
* more data to append to this strip before we are done
* depending on how we are getting called.
*/
if (!SeekOK(tif, td->td_stripoffset[strip])) {
TIFFErrorExt(tif->tif_clientdata, module,
"Seek error at scanline %lu",
(unsigned long)tif->tif_row);
return (0);
}
}
else
{
/*
* Seek to end of file, and set that as our location to
* write this strip.
*/
td->td_stripoffset[strip] = TIFFSeekFile(tif, 0, SEEK_END);
}
tif->tif_curoff = td->td_stripoffset[strip];
/*
* We are starting a fresh strip/tile, so set the size to zero.
*/
td->td_stripbytecount[strip] = 0;
}
m = tif->tif_curoff+cc;