From c940cc8b6c0a2983c1ec974f1b3f019795dd4cff Mon Sep 17 00:00:00 2001
From: Matthieu Herrb <matthieu@herrb.eu>
Date: Tue, 18 Aug 2020 14:49:04 +0200
Subject: [PATCH] Fix XIChangeHierarchy() integer underflow

CVE-2020-14346 / ZDI-CAN-11429

This vulnerability was discovered by:
Jan-Niklas Sohn working with Trend Micro Zero Day Initiative

Signed-off-by: Matthieu Herrb <matthieu@herrb.eu>
---
 Xi/xichangehierarchy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Xi/xichangehierarchy.c b/Xi/xichangehierarchy.c
index cbdd91258..504defe56 100644
--- a/Xi/xichangehierarchy.c
+++ b/Xi/xichangehierarchy.c
@@ -423,7 +423,7 @@ ProcXIChangeHierarchy(ClientPtr client)
     if (!stuff->num_changes)
         return rc;
 
-    len = ((size_t)stuff->length << 2) - sizeof(xXIChangeHierarchyReq);
+    len = ((size_t)client->req_len << 2) - sizeof(xXIChangeHierarchyReq);
 
     any = (xXIAnyHierarchyChangeInfo *) &stuff[1];
     while (stuff->num_changes--) {