qga-win: fix "guest-get-fsinfo" wrong filesystem type

This patch handles the case where unmounted volumes exist,
where in that case GetVolumePathNamesForVolumeName returns
empty path, GetVolumeInformation will use the current working
directory instead.
This patch fixes the issue by opening a handle to the volumes,
and using GetVolumeInformationByHandleW instead.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1746667Signed-off-by: NBasil Salman <bsalman@redhat.com>
Signed-off-by: NBasil Salman <basil@daynix.com>
*fix crash when guest_build_fsinfo() sets errp multiple times
*make new error message more distinct from existing ones
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

qga/commands-win32.c

@@ -958,11 +958,13 @@ static GuestFilesystemInfo *build_guest_fsinfo(char *guid, Error **errp)
 {
     DWORD info_size;
     char mnt, *mnt_point;
+    wchar_t wfs_name[32];
     char fs_name[32];
-    char vol_info[MAX_PATH+1];
+    wchar_t vol_info[MAX_PATH + 1];
     size_t len;
     uint64_t i64FreeBytesToCaller, i64TotalBytes, i64FreeBytes;
     GuestFilesystemInfo *fs = NULL;
+    HANDLE hLocalDiskHandle = NULL;
 
     GetVolumePathNamesForVolumeName(guid, (LPCH)&mnt, 0, &info_size);
     if (GetLastError() != ERROR_MORE_DATA) {
@@ -977,18 +979,27 @@ static GuestFilesystemInfo *build_guest_fsinfo(char *guid, Error **errp)
         goto free;
     }
 
+    hLocalDiskHandle = CreateFile(guid, 0 , 0, NULL, OPEN_EXISTING,
+                                  FILE_ATTRIBUTE_NORMAL |
+                                  FILE_FLAG_BACKUP_SEMANTICS, NULL);
+    if (INVALID_HANDLE_VALUE == hLocalDiskHandle) {
+        error_setg_win32(errp, GetLastError(), "failed to get handle for volume");
+        goto free;
+    }
+
     len = strlen(mnt_point);
     mnt_point[len] = '\\';
     mnt_point[len+1] = 0;
-    if (!GetVolumeInformation(mnt_point, vol_info, sizeof(vol_info), NULL, NULL,
-                              NULL, (LPSTR)&fs_name, sizeof(fs_name))) {
+
+    if (!GetVolumeInformationByHandleW(hLocalDiskHandle, vol_info,
+                                       sizeof(vol_info), NULL, NULL, NULL,
+                                       (LPWSTR) & wfs_name, sizeof(wfs_name))) {
         if (GetLastError() != ERROR_NOT_READY) {
             error_setg_win32(errp, GetLastError(), "failed to get volume info");
         }
         goto free;
     }
 
-    fs_name[sizeof(fs_name) - 1] = 0;
     fs = g_malloc(sizeof(*fs));
     fs->name = g_strdup(guid);
     fs->has_total_bytes = false;
@@ -1007,9 +1018,11 @@ static GuestFilesystemInfo *build_guest_fsinfo(char *guid, Error **errp)
             fs->has_used_bytes = true;
         }
     }
+    wcstombs(fs_name, wfs_name, sizeof(wfs_name));
     fs->type = g_strdup(fs_name);
     fs->disk = build_guest_disk_info(guid, errp);
 free:
+    CloseHandle(hLocalDiskHandle);
     g_free(mnt_point);
     return fs;
 }
@@ -1027,8 +1040,12 @@ GuestFilesystemInfoList *qmp_guest_get_fsinfo(Error **errp)
     }
 
     do {
-        GuestFilesystemInfo *info = build_guest_fsinfo(guid, errp);
-        if (info == NULL) {
+        Error *local_err = NULL;
+        GuestFilesystemInfo *info = build_guest_fsinfo(guid, &local_err);
+        if (local_err) {
+            g_debug("failed to get filesystem info, ignoring error: %s",
+                    error_get_pretty(local_err));
+            error_free(local_err);
             continue;
         }
         new = g_malloc(sizeof(*ret));