From 641610b961a732bb68f111536ebf8c42be20f05b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20=C3=85dahl?= <jadahl@gmail.com>
Date: Wed, 16 Sep 2020 17:35:49 +0200
Subject: [PATCH 4/4] zlib: Clear buffer pointers on cleanup (#444)

The pointers to the buffers were freed, and the size fields were set to
0, but the buffer pointers themsef was not set to NULL, when shutting
down, meaning the next time used, NULL checks would not tell whether the
pointer is valid. This caused crashes ending with

  #0  0x00007ffff73729e5 in raise () from /lib64/libc.so.6
  #1  0x00007ffff735b895 in abort () from /lib64/libc.so.6
  #2  0x00007ffff73b6857 in __libc_message () from /lib64/libc.so.6
  #3  0x00007ffff73bdd7c in malloc_printerr () from /lib64/libc.so.6
  #4  0x00007ffff73c2f1a in realloc () from /lib64/libc.so.6
  #5  0x00007ffff78b558e in rfbSendOneRectEncodingZlib (cl=0x4a4b80, x=0, y=0, w=800, h=40) at /home/jonas/Dev/gnome/libvncserver/libvncserver/zlib.c:106
  #6  0x00007ffff78b5dec in rfbSendRectEncodingZlib (cl=0x4a4b80, x=0, y=0, w=800, h=600) at /home/jonas/Dev/gnome/libvncserver/libvncserver/zlib.c:308
  #7  0x00007ffff7899453 in rfbSendFramebufferUpdate (cl=0x4a4b80, givenUpdateRegion=0x49ef70) at /home/jonas/Dev/gnome/libvncserver/libvncserver/rfbserver.c:3264
  #8  0x00007ffff789079d in rfbUpdateClient (cl=0x4a4b80) at /home/jonas/Dev/gnome/libvncserver/libvncserver/main.c:1275
  #9  0x00007ffff78905f5 in rfbProcessEvents (screen=0x4d5790, usec=0) at /home/jonas/Dev/gnome/libvncserver/libvncserver/main.c:1251
---
 libvncserver/zlib.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libvncserver/zlib.c b/libvncserver/zlib.c
index d24d7d15..5c3a8236 100644
--- a/libvncserver/zlib.c
+++ b/libvncserver/zlib.c
@@ -64,11 +64,13 @@ void rfbZlibCleanup(rfbScreenInfoPtr screen)
 {
   if (zlibBeforeBufSize) {
     free(zlibBeforeBuf);
+    zlibBeforeBuf = NULL;
     zlibBeforeBufSize=0;
   }
   if (zlibAfterBufSize) {
     zlibAfterBufSize=0;
     free(zlibAfterBuf);
+    zlibAfterBuf = NULL;
   }
 }
 
-- 
2.28.0