From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58773) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y8v26-0005tK-9P for qemu-devel@nongnu.org; Wed, 07 Jan 2015 13:08:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y8v21-0006Kz-7V for qemu-devel@nongnu.org; Wed, 07 Jan 2015 13:08:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57873) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y8v21-0006Kr-07 for qemu-devel@nongnu.org; Wed, 07 Jan 2015 13:08:33 -0500 Message-ID: <54AD7618.4060802@redhat.com> Date: Wed, 07 Jan 2015 13:08:24 -0500 From: John Snow MIME-Version: 1.0 References: <1420566495-13284-1-git-send-email-peter@lekensteyn.nl> <1420566495-13284-9-git-send-email-peter@lekensteyn.nl> In-Reply-To: <1420566495-13284-9-git-send-email-peter@lekensteyn.nl> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 08/12] block/dmg: fix sector data offset calculation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Wu , qemu-devel@nongnu.org Cc: Kevin Wolf , Stefan Hajnoczi On 01/06/2015 12:48 PM, Peter Wu wrote: > 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 > --- > v2: use sector and data offset as provided by the BLKX header. This > allows us to drop last_in_offset. The previous heuristics to detect > relative offsets is not needed anymore. Squashed the data fork > offset length check into this patch. > --- > block/dmg.c | 26 ++++++++++++++++++++------ > 1 file changed, 20 insertions(+), 6 deletions(-) > > diff --git a/block/dmg.c b/block/dmg.c > index 57feb1b..130efac 100644 > --- a/block/dmg.c > +++ b/block/dmg.c > @@ -188,7 +188,7 @@ 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; > @@ -203,6 +203,8 @@ 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) */ > @@ -211,8 +213,12 @@ 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); > @@ -228,7 +234,6 @@ 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]; Great! > ds->last_out_offset = s->sectors[i - 1] + > s->sectorcounts[i - 1]; > } > @@ -255,7 +260,7 @@ 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); > @@ -413,7 +418,7 @@ 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; > @@ -425,6 +430,15 @@ 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) { > Reviewed-by: John Snow