File _service:obs_scm:backport-CVE-2021-4011.patch of Package xorg-x11-server

From e56f61c79fc3cee26d83cda0f84ae56d5979f768 Mon Sep 17 00:00:00 2001
From: Povilas Kanapickas <povilas@radix.lt>
Date: Tue, 14 Dec 2021 15:00:00 +0200
Subject: [PATCH] record: Fix out of bounds access in SwapCreateRegister()

ZDI-CAN-14952, CVE-2021-4011

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

Signed-off-by: Povilas Kanapickas <povilas@radix.lt>
---
 record/record.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/record/record.c b/record/record.c
index be154525d..e123867a7 100644
--- a/record/record.c
+++ b/record/record.c
@@ -2516,8 +2516,8 @@ SwapCreateRegister(ClientPtr client, xRecordRegisterClientsReq * stuff)
         swapl(pClientID);
     }
     if (stuff->nRanges >
-        client->req_len - bytes_to_int32(sz_xRecordRegisterClientsReq)
-        - stuff->nClients)
+        (client->req_len - bytes_to_int32(sz_xRecordRegisterClientsReq)
+        - stuff->nClients) / bytes_to_int32(sz_xRecordRange))
         return BadLength;
     RecordSwapRanges((xRecordRange *) pClientID, stuff->nRanges);
     return Success;
-- 
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