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block/dmg: fix sector data offset calculation 

This patch addresses two issues:

 - The data fork offset was not taken into account, resulting in failure
   to read an InstallESD.dmg file (5164763151 bytes) which had a
   non-zero DataForkOffset field.
 - The offset of the previous block ("partition") was unconditionally
   added to the current block because older files would start the input
   offset of a new block at zero. Newer files (including vlc-2.1.5.dmg,
   tuxpaint-0.9.15-macosx.dmg and OS X Yosemite [MAS].dmg) failed in
   reads because these files have chunk offsets, relative to the begin
   of a data fork.

Now the data offset of the mish is taken into account. While we could
check that the data_offset is within the data fork, let's not do that
here as it would only result in parse failures on invalid files (rather
than gracefully handling such bad files). dmg_read will error out if
the offset is incorrect.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 1420566495-13284-9-git-send-email-peter@lekensteyn.nl
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Peter Wu 2015-01-06 18:48:11 +01:00 committed by Kevin Wolf
parent 8daf425794
commit c6d34865fa
1 changed files with 20 additions and 6 deletions
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26
block/dmg.c
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@ -186,7 +186,7 @@ static int64_t dmg_find_koly_offset(BlockDriverState *file_bs, Error **errp)
typedef struct DmgHeaderState {
/* used internally by dmg_read_mish_block to remember offsets of blocks
* across calls */
uint64_t last_in_offset;
uint64_t data_fork_offset;
uint64_t last_out_offset;
/* exported for dmg_open */
uint32_t max_compressed_size;
@ -201,6 +201,8 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds,
size_t new_size;
uint32_t chunk_count;
int64_t offset = 0;
uint64_t data_offset;
uint64_t in_offset = ds->data_fork_offset;
type = buff_read_uint32(buffer, offset);
/* skip data that is not a valid MISH block (invalid magic or too small) */
@ -209,8 +211,12 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds,
return 0;
}
offset += 4;
offset += 200;
/* location in data fork for (compressed) blob (in bytes) */
data_offset = buff_read_uint64(buffer, offset + 0x18);
in_offset += data_offset;
/* move to begin of chunk entries */
offset += 204;
chunk_count = (count - 204) / 40;
new_size = sizeof(uint64_t) * (s->n_chunks + chunk_count);
@ -226,7 +232,6 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds,
if (s->types[i] != 0x80000005 && s->types[i] != 1 &&
s->types[i] != 2) {
if (s->types[i] == 0xffffffff && i > 0) {
ds->last_in_offset = s->offsets[i - 1] + s->lengths[i - 1];
ds->last_out_offset = s->sectors[i - 1] +
s->sectorcounts[i - 1];
}
@ -253,7 +258,7 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds,
}
s->offsets[i] = buff_read_uint64(buffer, offset);
s->offsets[i] += ds->last_in_offset;
s->offsets[i] += in_offset;
offset += 8;
s->lengths[i] = buff_read_uint64(buffer, offset);
@ -412,7 +417,7 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
s->n_chunks = 0;
s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;
/* used by dmg_read_mish_block to keep track of the current I/O position */
ds.last_in_offset = 0;
ds.data_fork_offset = 0;
ds.last_out_offset = 0;
ds.max_compressed_size = 1;
ds.max_sectors_per_chunk = 1;
@ -424,6 +429,15 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
goto fail;
}
/* offset of data fork (DataForkOffset) */
ret = read_uint64(bs, offset + 0x18, &ds.data_fork_offset);
if (ret < 0) {
goto fail;
} else if (ds.data_fork_offset > offset) {
ret = -EINVAL;
goto fail;
}
/* offset of resource fork (RsrcForkOffset) */
ret = read_uint64(bs, offset + 0x28, &rsrc_fork_offset);
if (ret < 0) {