From 5921dd2a1c9d57fa2712db03633ed13b128eb2ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
 <marmarek@invisiblethingslab.com>
Date: Mon, 20 Jun 2016 22:00:57 +0200
Subject: [PATCH] core: validate dom0 drive path before starting VM

This is very easy if the file/device is in dom0, so do it to avoid
cryptic startup error (`libvirtError: internal error: libxenlight failed
to create domain`).

Fixes QubesOS/qubes-issues#1619
---
 core-modules/01QubesHVm.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/core-modules/01QubesHVm.py b/core-modules/01QubesHVm.py
index 2a6e9f04..c98b67b5 100644
--- a/core-modules/01QubesHVm.py
+++ b/core-modules/01QubesHVm.py
@@ -312,7 +312,16 @@ class QubesHVm(QubesResizableVm):
         else:
             return -1
 
+    def validate_drive_path(self, drive):
+        drive_type, drive_domain, drive_path = drive.split(':', 2)
+        if drive_domain == 'dom0':
+            if not os.path.exists(drive_path):
+                raise QubesException("Invalid drive path '{}'".format(
+                    drive_path))
+
     def start(self, *args, **kwargs):
+        if self.drive:
+            self.validate_drive_path(self.drive)
         # make it available to storage.prepare_for_vm_startup, which is
         # called before actually building VM libvirt configuration
         self.storage.drive = self.drive