From 5157ed047945aef5ee1116ce2737c649cbe28a3d Mon Sep 17 00:00:00 2001
From: Mark Kendall <mark.kendall@gmail.com>
Date: Wed, 12 Feb 2020 12:11:14 +0000
Subject: [PATCH] MythDRMDevice: Guard against invalid devices

---
 mythtv/libs/libmythui/platforms/mythdisplaydrm.cpp | 12 ++++++++++++
 mythtv/libs/libmythui/platforms/mythdrmdevice.cpp  |  6 ++++++
 mythtv/libs/libmythui/platforms/mythdrmdevice.h    |  2 ++
 3 files changed, 20 insertions(+)

diff --git a/mythtv/libs/libmythui/platforms/mythdisplaydrm.cpp b/mythtv/libs/libmythui/platforms/mythdisplaydrm.cpp
index 57880c97741..66fd2cc6955 100644
--- a/mythtv/libs/libmythui/platforms/mythdisplaydrm.cpp
+++ b/mythtv/libs/libmythui/platforms/mythdisplaydrm.cpp
@@ -8,6 +8,11 @@ MythDisplayDRM::MythDisplayDRM()
   : MythDisplay()
 {
     m_device = new MythDRMDevice(m_screen);
+    if (!m_device->IsValid())
+    {
+        delete m_device;
+        m_device = nullptr;
+    }
     Initialise();
 }
 
@@ -27,7 +32,14 @@ void MythDisplayDRM::ScreenChanged(QScreen *qScreen)
     }
 
     if (!m_device)
+    {
         m_device = new MythDRMDevice(m_screen);
+        if (!m_device->IsValid())
+        {
+            delete m_device;
+            m_device = nullptr;
+        }
+    }
 }
 
 void MythDisplayDRM::UpdateCurrentMode(void)
diff --git a/mythtv/libs/libmythui/platforms/mythdrmdevice.cpp b/mythtv/libs/libmythui/platforms/mythdrmdevice.cpp
index 5aa94aae4cc..b2a9d25d342 100644
--- a/mythtv/libs/libmythui/platforms/mythdrmdevice.cpp
+++ b/mythtv/libs/libmythui/platforms/mythdrmdevice.cpp
@@ -26,6 +26,7 @@ MythDRMDevice::MythDRMDevice(QScreen *qScreen, const QString& Device)
         return;
     }
 
+    m_valid = true;
     Authenticate();
     if (m_authenticated)
         LOG(VB_GENERAL, m_verbose, LOC + "Authenticated");
@@ -76,6 +77,11 @@ void MythDRMDevice::Close(void)
     m_fd = 0;
 }
 
+bool MythDRMDevice::IsValid(void) const
+{
+    return m_valid;
+}
+
 QString MythDRMDevice::GetSerialNumber(void) const
 {
     return m_serialNumber;
diff --git a/mythtv/libs/libmythui/platforms/mythdrmdevice.h b/mythtv/libs/libmythui/platforms/mythdrmdevice.h
index eb72fd0ec4b..7ab0c374ead 100644
--- a/mythtv/libs/libmythui/platforms/mythdrmdevice.h
+++ b/mythtv/libs/libmythui/platforms/mythdrmdevice.h
@@ -21,6 +21,7 @@ class MythDRMDevice : public ReferenceCounter
     explicit MythDRMDevice(QScreen *qScreen, const QString& Device = QString());
    ~MythDRMDevice() override;
 
+    bool     IsValid        (void) const;
     QString  GetSerialNumber(void) const;
     QScreen* GetScreen      (void) const;
     QSize    GetResolution  (void) const;
@@ -42,6 +43,7 @@ class MythDRMDevice : public ReferenceCounter
     drmModePropertyBlobPtr GetBlobProperty(drmModeConnectorPtr Connector, const QString& Property);
 
   private:
+    bool               m_valid         { false };
     QScreen*           m_screen        { nullptr };
     QString            m_deviceName    { };
     int                m_fd            { -1 };