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From 6fb76589c86264784014d8b555dc9c479c534898 Mon Sep 17 00:00:00 2001
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From: Jeffrey Cody <jcody@redhat.com>
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Date: Tue, 27 May 2014 19:05:11 +0200
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Subject: [PATCH 07/13] block: vhdx - account for identical header sections
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Jeffrey Cody <jcody@redhat.com>
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Message-id: <6a956eaa23796489845aaf8b0ef8aa390014e98b.1401217451.git.jcody@redhat.com>
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Patchwork-id: 59040
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O-Subject: [PATCH qemu-kvm RHEL7.1] block: vhdx - account for identical header sections
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Bugzilla: 1097020
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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The VHDX spec v1.00 declares that "a header is current if it is the only
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valid header or if it is valid and its SequenceNumber field is greater
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than the other header’s SequenceNumber field. The parser must only use
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data from the current header. If there is no current header, then the
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VHDX file is corrupt."
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However, the Disk2VHD tool from Microsoft creates a VHDX image file that
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has 2 identical headers, including matching checksums and matching
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sequence numbers. Likely, as a shortcut the tool is just writing the
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header twice, for the active and inactive headers, during the image
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creation. Technically, this should be considered a corrupt VHDX file
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(at least per the 1.00 spec, and that is how we currently treat it).
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But in order to accomodate images created with Disk2VHD, we can safely
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create an exception for this case. If we find identical sequence
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numbers, then we check the VHDXHeader-sized chunks of each 64KB header
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sections (we won't rely just on the crc32c to indicate the headers are
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the same). If they are identical, then we go ahead and use the first
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one.
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Reported-by: Nerijus Baliūnas <nerijus@users.sourceforge.net>
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Signed-off-by: Jeff Cody <jcody@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 6906046169ffa9d829beeeaafe1fadeba51669fb)
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Conflicts:
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block/vhdx.c
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Signed-off-by: Jeff Cody <jcody@redhat.com>
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---
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Brew: http://brewweb.devel.redhat.com/brew/taskinfo?taskID=7505809
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BZ: 1097020
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Conflict notes: the conflict was with the ret value; current upstream
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removed that in favor of passing in errp to the function
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block/vhdx.c | 11 +++++++++--
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1 file changed, 9 insertions(+), 2 deletions(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/vhdx.c | 11 +++++++++--
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1 files changed, 9 insertions(+), 2 deletions(-)
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diff --git a/block/vhdx.c b/block/vhdx.c
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index 66a25c9..21ad6ad 100644
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--- a/block/vhdx.c
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+++ b/block/vhdx.c
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@@ -473,8 +473,15 @@ static int vhdx_parse_header(BlockDriverState *bs, BDRVVHDXState *s)
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} else if (h2_seq > h1_seq) {
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s->curr_header = 1;
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} else {
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- ret = -EINVAL;
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- goto fail;
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+ /* The Microsoft Disk2VHD tool will create 2 identical
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+ * headers, with identical sequence numbers. If the headers are
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+ * identical, don't consider the file corrupt */
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+ if (!memcmp(header1, header2, sizeof(VHDXHeader))) {
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+ s->curr_header = 0;
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+ } else {
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+ ret = -EINVAL;
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+ goto fail;
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+ }
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}
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}
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--
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1.7.1
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