Bug#929499: Crash in XKeycodeToKeysym()

[Mike Gabriel <mike.gabriel@das-netzwerkteam.de>]

Package: src:nx-libs
Version: 2:3.5.99.19-2
Severity: important
Tags: patch fixed-upstream
Forwarded: https://github.com/ArcticaProject/nx-libs/issues/801

In libnx-x11, it was found that pointers (dpy, xkb) are referenced  
without them being checked for being NULL or valid object pointers.

This was fixed by this upstream PR:
https://github.com/ArcticaProject/nx-libs/pull/809

Mike
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>From 20353e96a390a029f7b3b18fc7ddd82eae98b935 Mon Sep 17 00:00:00 2001
From: Ulrich Sibiller <uli42@gmx.de>
Date: Wed, 15 May 2019 19:54:24 +0200
Subject: [PATCH 2/2] libNX_X11: add additional checks for dpy and xkb

We have seen crashes during session shutdown/connection problems
here. These patches should avoid them. There's no proper way to test
them, but they should do no harm..

Fixes ArcticaProject/nx-libs#801
Fixes https://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=695
---
 nx-X11/lib/src/xkb/XKBBind.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/nx-X11/lib/src/xkb/XKBBind.c b/nx-X11/lib/src/xkb/XKBBind.c
index 068e8f2a0..ffe5ad9d7 100644
--- a/nx-X11/lib/src/xkb/XKBBind.c
+++ b/nx-X11/lib/src/xkb/XKBBind.c
@@ -108,7 +108,21 @@ XKeycodeToKeysym(Display *dpy,
 
     _XkbCheckPendingRefresh(dpy, dpy->xkb_info);
 
+#ifdef NX_TRANS_SOCKET
+    /*
+       check again, we have seen cases where the connection broke
+       during CheckPendingEvents(), followed by a crash when accessing
+       dpy. See https://github.com/ArcticaProject/nx-libs/issues/801
+    */
+    if (_XkbUnavailable(dpy))
+        return _XKeycodeToKeysym(dpy, kc, col);
+#endif
+
     xkb = dpy->xkb_info->desc;
+#ifdef NX_TRANS_SOCKET
+    if (xkb == NULL)
+        return _XKeycodeToKeysym(dpy, kc, col);
+#endif
     if ((kc < xkb->min_key_code) || (kc > xkb->max_key_code))
         return NoSymbol;
 
-- 
2.20.1

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