From 85b776571487f52e756f68a069c768757369bfe3 Mon Sep 17 00:00:00 2001
From: Matthieu Herrb <matthieu@herrb.eu>
Date: Thu, 10 Oct 2024 10:37:28 +0200
Subject: [PATCH] xkb: Fix buffer overflow in _XkbSetCompatMap()
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origin: https://gitlab.freedesktop.org/xorg/xserver/-/commit/85b776571487f52e756f68a069c768757369bfe3

The _XkbSetCompatMap() function attempts to resize the `sym_interpret`
buffer.

However, It didn't update its size properly. It updated `num_si` only,
without updating `size_si`.

This may lead to local privilege escalation if the server is run as root
or remote code execution (e.g. x11 over ssh).

CVE-2024-9632, ZDI-CAN-24756

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

Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Tested-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: José Expósito <jexposit@redhat.com>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1733>
---
 xkb/xkb.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/xkb/xkb.c b/xkb/xkb.c
index 868d7c1e64..aaf9716b36 100644
--- a/xkb/xkb.c
+++ b/xkb/xkb.c
@@ -2990,13 +2990,13 @@ _XkbSetCompatMap(ClientPtr client, DeviceIntPtr dev,
         XkbSymInterpretPtr sym;
         unsigned int skipped = 0;
 
-        if ((unsigned) (req->firstSI + req->nSI) > compat->num_si) {
-            compat->num_si = req->firstSI + req->nSI;
+        if ((unsigned) (req->firstSI + req->nSI) > compat->size_si) {
+            compat->num_si = compat->size_si = req->firstSI + req->nSI;
             compat->sym_interpret = reallocarray(compat->sym_interpret,
-                                                 compat->num_si,
+                                                 compat->size_si,
                                                  sizeof(XkbSymInterpretRec));
             if (!compat->sym_interpret) {
-                compat->num_si = 0;
+                compat->num_si = compat->size_si = 0;
                 return BadAlloc;
             }
         }
-- 
GitLab