From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36121) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WHkEi-0002U9-Nk for qemu-devel@nongnu.org; Sun, 23 Feb 2014 20:21:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WHkEe-0005nz-3E for qemu-devel@nongnu.org; Sun, 23 Feb 2014 20:21:36 -0500 Sender: fluxion From: Michael Roth Date: Sun, 23 Feb 2014 19:21:09 -0600 Message-Id: <1393204873-13367-3-git-send-email-mdroth@linux.vnet.ibm.com> In-Reply-To: <1393204873-13367-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1393204873-13367-1-git-send-email-mdroth@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 2/6] qga: vss-win32: Fix interference with snapshot creation by other VSS requesters List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: aliguori@amazon.com, mprivozn@redhat.com, qemu-stable@nongnu.org, armbru@redhat.com, tomoki.sekiyama@hds.com, mmishael@redhat.com From: Tomoki Sekiyama 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 Reviewed-by: Gal Hammer Reviewed-by: Yan Vugenfirer Cc: qemu-stable@nongnu.org Signed-off-by: Michael Roth --- 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