kernel32: Handle device paths in GetVolumePathName.

dlls/kernel32/tests/volume.c

@@ -675,6 +675,14 @@ static void test_GetVolumePathNameA(void)
             "InvalidDrive:\\AnInvalidFolder", "%CurrentDrive%\\", sizeof(volume_path),
             NO_ERROR, NO_ERROR
         },
+        { /* test 18: a reasonable device path */
+            "\\??\\CdRom0", "%CurrentDrive%\\", sizeof(volume_path),
+            NO_ERROR, NO_ERROR
+        },
+        { /* test 19: an unreasonable device path */
+            "\\??\\ReallyBogus", "%CurrentDrive%\\", sizeof(volume_path),
+            NO_ERROR, NO_ERROR
+        },
     };
     BOOL ret, success;
     DWORD error;

dlls/kernel32/volume.c

@@ -1817,6 +1817,7 @@ BOOL WINAPI GetVolumePathNameA(LPCSTR filename, LPSTR volumepathname, DWORD bufl
  */
 BOOL WINAPI GetVolumePathNameW(LPCWSTR filename, LPWSTR volumepathname, DWORD buflen)
 {
+    static const WCHAR deviceprefixW[] = { '\\','?','?','\\',0 };
     static const WCHAR ntprefixW[] = { '\\','\\','?','\\',0 };
     WCHAR fallbackpathW[] = { 'C',':','\\',0 };
     NTSTATUS status = STATUS_SUCCESS;
@@ -1892,9 +1893,9 @@ BOOL WINAPI GetVolumePathNameW(LPCWSTR filename, LPWSTR volumepathname, DWORD bu
         WCHAR cwdW[MAX_PATH];
 
         /* the path was completely invalid */
-        if (filename[0] == '\\')
+        if (filename[0] == '\\' && strncmpW(deviceprefixW, filename, strlenW(deviceprefixW)) != 0)
         {
-            /* NT-style paths fail */
+            /* NT-style paths (that are not device paths) fail */
             status = STATUS_OBJECT_NAME_INVALID;
             goto cleanup;
         }