From a659519ffa3eae4c94218b03e704a2b6d26adf6f Mon Sep 17 00:00:00 2001
From: Olivier Fourdan <ofourdan@redhat.com>
Date: Wed, 18 Jun 2025 08:39:02 +0200
Subject: [PATCH] os: Check for integer overflow on BigRequest length

Check for another possible integer overflow once we get a complete xReq
with BigRequest.

Related to CVE-2025-49176

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Suggested-by: Peter Harris <pharris2@rocketsoftware.com>
(cherry picked from commit 4fc4d76b2c7aaed61ed2653f997783a3714c4fe1)

Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2029>
---
 os/io.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/os/io.c b/os/io.c
index 26f9161ef..83986af92 100644
--- a/os/io.c
+++ b/os/io.c
@@ -395,6 +395,8 @@ ReadRequestFromClient(ClientPtr client)
                     needed = get_big_req_len(request, client);
             }
             client->req_len = needed;
+            if (needed > MAXINT >> 2)
+                return -(BadLength);
             needed <<= 2;
         }
         if (gotnow < needed) {