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[Qemu-stable] [PATCH 2/6] qga: vss-win32: Fix interference with snapshot
From: |
Michael Roth |
Subject: |
[Qemu-stable] [PATCH 2/6] qga: vss-win32: Fix interference with snapshot creation by other VSS requesters |
Date: |
Sun, 23 Feb 2014 19:21:09 -0600 |
From: Tomoki Sekiyama <address@hidden>
When a VSS requester such as vshadow.exe or diskshadow.exe requests to
create disk snapshots, Windows may choose qemu-ga VSS provider if it is
only provider registered on the system. However, because it provides only a
function to freeze the filesystem, the snapshotting fails.
This patch adds a check into CQGAVssProvider::IsVolumeSupported() to reject
the request from other VSS requesters, so that the other provider is chosen.
The check of requester is done by confirming event channels between
qemu-ga's requester and provider established. To ensure that the events are
initialized when CQGAVssProvider::IsVolumeSupported() is called, it moves
the initialization earlier.
Signed-off-by: Tomoki Sekiyama <address@hidden>
Reviewed-by: Gal Hammer <address@hidden>
Reviewed-by: Yan Vugenfirer <address@hidden>
Cc: address@hidden
Signed-off-by: Michael Roth <address@hidden>
---
qga/vss-win32/provider.cpp | 11 ++++++++-
qga/vss-win32/requester.cpp | 52 +++++++++++++++++++++----------------------
2 files changed, 36 insertions(+), 27 deletions(-)
diff --git a/qga/vss-win32/provider.cpp b/qga/vss-win32/provider.cpp
index c3030d8..b233646 100644
--- a/qga/vss-win32/provider.cpp
+++ b/qga/vss-win32/provider.cpp
@@ -291,8 +291,17 @@ STDMETHODIMP CQGAVssProvider::BeginPrepareSnapshot(
STDMETHODIMP CQGAVssProvider::IsVolumeSupported(
VSS_PWSZ pwszVolumeName, BOOL *pbSupportedByThisProvider)
{
- *pbSupportedByThisProvider = TRUE;
+ HANDLE hEventFrozen;
+
+ /* Check if a requester is qemu-ga by whether an event is created */
+ hEventFrozen = OpenEvent(EVENT_ALL_ACCESS, FALSE, EVENT_NAME_FROZEN);
+ if (!hEventFrozen) {
+ *pbSupportedByThisProvider = FALSE;
+ return S_OK;
+ }
+ CloseHandle(hEventFrozen);
+ *pbSupportedByThisProvider = TRUE;
return S_OK;
}
diff --git a/qga/vss-win32/requester.cpp b/qga/vss-win32/requester.cpp
index 0a55447..922e74d 100644
--- a/qga/vss-win32/requester.cpp
+++ b/qga/vss-win32/requester.cpp
@@ -252,6 +252,32 @@ void requester_freeze(int *num_vols, ErrorSet *errset)
CoInitialize(NULL);
+ /* Allow unrestricted access to events */
+ InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
+ SetSecurityDescriptorDacl(&sd, TRUE, NULL, FALSE);
+ sa.nLength = sizeof(sa);
+ sa.lpSecurityDescriptor = &sd;
+ sa.bInheritHandle = FALSE;
+
+ vss_ctx.hEventFrozen = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_FROZEN);
+ if (!vss_ctx.hEventFrozen) {
+ err_set(errset, GetLastError(), "failed to create event %s",
+ EVENT_NAME_FROZEN);
+ goto out;
+ }
+ vss_ctx.hEventThaw = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_THAW);
+ if (!vss_ctx.hEventThaw) {
+ err_set(errset, GetLastError(), "failed to create event %s",
+ EVENT_NAME_THAW);
+ goto out;
+ }
+ vss_ctx.hEventTimeout = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_TIMEOUT);
+ if (!vss_ctx.hEventTimeout) {
+ err_set(errset, GetLastError(), "failed to create event %s",
+ EVENT_NAME_TIMEOUT);
+ goto out;
+ }
+
assert(pCreateVssBackupComponents != NULL);
hr = pCreateVssBackupComponents(&vss_ctx.pVssbc);
if (FAILED(hr)) {
@@ -362,32 +388,6 @@ void requester_freeze(int *num_vols, ErrorSet *errset)
goto out;
}
- /* Allow unrestricted access to events */
- InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
- SetSecurityDescriptorDacl(&sd, TRUE, NULL, FALSE);
- sa.nLength = sizeof(sa);
- sa.lpSecurityDescriptor = &sd;
- sa.bInheritHandle = FALSE;
-
- vss_ctx.hEventFrozen = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_FROZEN);
- if (!vss_ctx.hEventFrozen) {
- err_set(errset, GetLastError(), "failed to create event %s",
- EVENT_NAME_FROZEN);
- goto out;
- }
- vss_ctx.hEventThaw = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_THAW);
- if (!vss_ctx.hEventThaw) {
- err_set(errset, GetLastError(), "failed to create event %s",
- EVENT_NAME_THAW);
- goto out;
- }
- vss_ctx.hEventTimeout = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_TIMEOUT);
- if (!vss_ctx.hEventTimeout) {
- err_set(errset, GetLastError(), "failed to create event %s",
- EVENT_NAME_TIMEOUT);
- goto out;
- }
-
/*
* Start VSS quiescing operations.
* CQGAVssProvider::CommitSnapshots will kick vss_ctx.hEventFrozen
--
1.7.9.5
- [Qemu-stable] [PULL 0/6] qemu-ga: various fixes, and serial support for w32, Michael Roth, 2014/02/23
- [Qemu-stable] [PATCH 1/6] qga: vss-win32: Use NULL as an invalid pointer for OpenEvent and CreateEvent, Michael Roth, 2014/02/23
- [Qemu-stable] [PATCH 2/6] qga: vss-win32: Fix interference with snapshot creation by other VSS requesters,
Michael Roth <=
- [Qemu-stable] [PATCH 3/6] qga: vss-win32: Fix interference with snapshot deletion by other VSS request, Michael Roth, 2014/02/23
- [Qemu-stable] [PATCH 5/6] qga: Fix memory allocation pasto, Michael Roth, 2014/02/23
- [Qemu-stable] [PATCH 4/6] qga: Don't require 'time' argument in guest-set-time command, Michael Roth, 2014/02/23
- [Qemu-stable] [PATCH 6/6] qemu-ga: isa-serial support on Windows, Michael Roth, 2014/02/23
- Re: [Qemu-stable] [Qemu-devel] [PULL 0/6] qemu-ga: various fixes, and serial support for w32, Peter Maydell, 2014/02/25