kernel32: Handle semi-DOS paths in GetVolumePathName.

dlls/kernel32/tests/volume.c

@@ -663,6 +663,14 @@ static void test_GetVolumePathNameA(void)
             "\\\\ReallyBogus\\InvalidDrive:\\" /* win2k, winxp */, sizeof(volume_path),
             ERROR_INVALID_NAME, NO_ERROR
         },
+        { /* test 15: poor quality input, valid output, valid output length, different drive */
+            "D::", "D:\\", sizeof(volume_path),
+            NO_ERROR, NO_ERROR
+        },
+        { /* test 16: unused drive letter */
+            "M::", "C:\\", 4,
+            ERROR_FILE_NOT_FOUND, ERROR_MORE_DATA
+        },
     };
     BOOL ret, success;
     DWORD error;

dlls/kernel32/volume.c

@@ -1818,7 +1818,7 @@ BOOL WINAPI GetVolumePathNameA(LPCSTR filename, LPSTR volumepathname, DWORD bufl
 BOOL WINAPI GetVolumePathNameW(LPCWSTR filename, LPWSTR volumepathname, DWORD buflen)
 {
     static const WCHAR ntprefixW[] = { '\\','\\','?','\\',0 };
-    static const WCHAR fallbackpathW[] = { 'C',':','\\',0 };
+    WCHAR fallbackpathW[] = { 'C',':','\\',0 };
     NTSTATUS status = STATUS_SUCCESS;
     WCHAR *volumenameW = NULL, *c;
     int pos, last_pos, stop_pos;
@@ -1897,7 +1897,17 @@ BOOL WINAPI GetVolumePathNameW(LPCWSTR filename, LPWSTR volumepathname, DWORD bu
             goto cleanup;
         }
 
-        /* DOS-style paths revert to C:\ (anything not beginning with a slash) */
+        /* DOS-style paths (anything not beginning with a slash) have fallback replies */
+        if (filename[1] == ':')
+        {
+            /* if the path is semi-sane (X:) then use the given drive letter (if it is mounted) */
+            fallbackpathW[0] = filename[0];
+            if (!isalphaW(filename[0]) || GetDriveTypeW( fallbackpathW ) == DRIVE_NO_ROOT_DIR)
+            {
+                status = STATUS_OBJECT_NAME_NOT_FOUND;
+                goto cleanup;
+            }
+        }
         last_pos = strlenW(fallbackpathW) - 1; /* points to \\ */
         filename = fallbackpathW;
         status = STATUS_SUCCESS;