From 3ab144fe22a867a0ffcce396302b62b0f2ac4c29 Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Fri, 1 Nov 2013 14:23:16 +0100
Subject: [PATCH 28/81] qcow2: Unset zero_beyond_eof in save_vmstate

RH-Author: Max Reitz <mreitz@redhat.com>
Message-id: <1383315797-30938-3-git-send-email-mreitz@redhat.com>
Patchwork-id: 55217
O-Subject: [RHEL-7.0 qemu-kvm PATCH 2/3] qcow2: Unset zero_beyond_eof in save_vmstate
Bugzilla: 1025740
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Alex Williamson <alex.williamson@redhat.com>

BZ: 1025740

Saving the VM state is done using bdrv_pwrite. This function may perform
a read-modify-write, which in this case results in data being read from
beyond the end of the virtual disk. Since we are actually trying to
access an area which is not a part of the virtual disk, zero_beyond_eof
has to be set to false before performing the partial write, otherwise
the VM state may become corrupted.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 6e13610aa454beba52944e8df6d93158d68ab911)

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/qcow2.c | 3 +++
 1 file changed, 3 insertions(+)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block/qcow2.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index f4adf35..c2728c9 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1718,12 +1718,15 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
     BDRVQcowState *s = bs->opaque;
     int64_t total_sectors = bs->total_sectors;
     int growable = bs->growable;
+    bool zero_beyond_eof = bs->zero_beyond_eof;
     int ret;
 
     BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
     bs->growable = 1;
+    bs->zero_beyond_eof = false;
     ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov);
     bs->growable = growable;
+    bs->zero_beyond_eof = zero_beyond_eof;
 
     /* bdrv_co_do_writev will have increased the total_sectors value to include
      * the VM state - the VM state is however not an actual part of the block
-- 
1.7.1