Make WriteEventsToClient/WriteToClient no-op on fake or dead clients.

 This matches the test in TryClientEvents, and is a superset of tests
 done by the callers of these functions. The consequence of forgetting
 these tests is a server crash, so they're always desirable. In my
 opinion, it's better to not require the callers to remember to do these
 checks.

 For callers that don't do very much work before calling WriteToClient or
 WriteEventsToClient, I've removed the redundant checks.

 Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=27497
 Signed-off-by: Jamey Sharp <jamey@minilop.net>
 Cc: Chris Wilson <chris@chris-wilson.co.uk>
 Reviewed-by: Julien Cristau <jcristau@debian.org>
 Reviewed-by: Adam Jackson <ajax@redhat.com>
 Backport to nx-libs: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>

1 files changed, 5 insertions, 3 deletions

diff --git a/nx-X11/programs/Xserver/os/io.c b/nx-X11/programs/Xserver/os/io.c
index 234ce8b58..4d12c6e89 100644
--- a/nx-X11/programs/Xserver/os/io.c
+++ b/nx-X11/programs/Xserver/os/io.c
@@ -859,14 +859,16 @@ SetCriticalOutputPending(void)
 int
 WriteToClient (ClientPtr who, int count, char *buf)
 {
-    OsCommPtr oc = (OsCommPtr)who->osPrivate;
-    ConnectionOutputPtr oco = oc->output;
+    OsCommPtr oc;
+    ConnectionOutputPtr oco;
     int padBytes;
 #ifdef DEBUG_COMMUNICATION
     Bool multicount = FALSE;
 #endif
-    if (!count)
+    if (!count || !who || who == serverClient || who->clientGone)
 	return(0);
+    oc = who->osPrivate;
+    oco = oc->output;
 #ifdef DEBUG_COMMUNICATION
     {
 	char info[128];