From a40e74d52a865fd4a9ca2a931be2d3a047c408f1 Mon Sep 17 00:00:00 2001 From: Jeffrey Cody Date: Tue, 27 May 2014 17:43:36 +0200 Subject: [PATCH 08/26] block: vhdx - account for identical header sections MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Jeffrey Cody Message-id: <6a422b735fecfd71827a5adebe0ab5a72e919f61.1401212443.git.jcody@redhat.com> Patchwork-id: 59033 O-Subject: [RHEL6 qemu-kvm PATCH] block: vhdx - account for identical header sections Bugzilla: 1097021 RH-Acked-by: Kevin Wolf RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Markus Armbruster The VHDX spec v1.00 declares that "a header is current if it is the only valid header or if it is valid and its SequenceNumber field is greater than the other header’s SequenceNumber field. The parser must only use data from the current header. If there is no current header, then the VHDX file is corrupt." However, the Disk2VHD tool from Microsoft creates a VHDX image file that has 2 identical headers, including matching checksums and matching sequence numbers. Likely, as a shortcut the tool is just writing the header twice, for the active and inactive headers, during the image creation. Technically, this should be considered a corrupt VHDX file (at least per the 1.00 spec, and that is how we currently treat it). But in order to accomodate images created with Disk2VHD, we can safely create an exception for this case. If we find identical sequence numbers, then we check the VHDXHeader-sized chunks of each 64KB header sections (we won't rely just on the crc32c to indicate the headers are the same). If they are identical, then we go ahead and use the first one. Reported-by: Nerijus Baliūnas Signed-off-by: Jeff Cody Signed-off-by: Kevin Wolf (cherry picked from commit 6906046169ffa9d829beeeaafe1fadeba51669fb) Conflicts: block/vhdx.c Signed-off-by: Jeff Cody --- RHEL67 Notes: Brew: http://brewweb.devel.redhat.com/brew/taskinfo?taskID=7505305 BZ: 1097021 Conflict notes: the conflict was with the ret value; current upstream removed that in favor of passing in errp to the function block/vhdx.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) Signed-off-by: Miroslav Rezanina --- block/vhdx.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-) diff --git a/block/vhdx.c b/block/vhdx.c index da4b71e..60744f4 100644 --- a/block/vhdx.c +++ b/block/vhdx.c @@ -322,8 +322,15 @@ static int vhdx_parse_header(BlockDriverState *bs, BDRVVHDXState *s) } else if (h2_seq > h1_seq) { s->curr_header = 1; } else { - ret = -EINVAL; - goto fail; + /* The Microsoft Disk2VHD tool will create 2 identical + * headers, with identical sequence numbers. If the headers are + * identical, don't consider the file corrupt */ + if (!memcmp(header1, header2, sizeof(VHDXHeader))) { + s->curr_header = 0; + } else { + ret = -EINVAL; + goto fail; + } } } -- 1.7.1