xserver/xkb
Peter Harris 432cb931cf xkb: fix buffer re-use in _XkbSetCompatMap
If the "compat" buffer has previously been truncated, there will be
unused space in the buffer. The code uses this space, but does not
update the number of valid entries in the buffer.

In the best case, this leads to the new compat entries being ignored. In the
worst case, if there are any "skipped" compat entries, the number of
valid entries will be corrupted, potentially leading to a buffer read
overrun when processing a future request.

Set the number of used "compat" entries when re-using previously
allocated space in the buffer.

CVE-2026-33999, ZDI-CAN-28593

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

Signed-off-by: Peter Harris <pharris2@rocketsoftware.com>
Acked-by: Olivier Fourdan <ofourdan@redhat.com>
(cherry picked from commit b024ae1749)

Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2178>
2026-04-14 15:12:24 +02:00
..
ddxBeep.c Drop trailing whitespaces 2014-11-12 10:25:00 +10:00
ddxCtrls.c Drop trailing whitespaces 2014-11-12 10:25:00 +10:00
ddxKillSrv.c Drop trailing whitespaces 2014-11-12 10:25:00 +10:00
ddxLEDs.c Drop trailing whitespaces 2014-11-12 10:25:00 +10:00
ddxLoad.c xkb: don't require a trailing slash for the XKM output dir 2021-04-09 17:37:29 +00:00
ddxPrivate.c Introduce a consistent coding style 2012-03-21 13:54:42 -07:00
ddxVT.c Drop trailing whitespaces 2014-11-12 10:25:00 +10:00
Makefile.am XKB: Remove component listing support 2012-11-19 12:12:28 +10:00
maprules.c xkb: fix check for appending '|' character when applying rules 2016-09-07 15:16:13 +10:00
meson.build Add a Meson build system alongside autotools. 2017-04-26 15:25:27 -07:00
README.compiled R6.6 is the Xorg base-line 2003-11-14 15:54:54 +00:00
xkb.c xkb: fix buffer re-use in _XkbSetCompatMap 2026-04-14 15:12:24 +02:00
xkb.h Move extension initialisation prototypes into extinit.h 2012-07-09 23:06:41 -07:00
xkbAccessX.c xkb: add hook to allow/deny AccessX key repeat 2016-06-03 09:39:42 +02:00
xkbActions.c xkb: Fix locked/latched indicator desync across multiple keyboards 2026-03-28 16:40:00 +00:00
XKBAlloc.c xkb: ensure XkbAllocNames sets num_rg to 0 on allocation failure 2025-04-08 09:50:29 +02:00
xkbDflts.h Use ARRAY_SIZE all over the tree 2017-10-30 13:45:20 -04:00
xkbEvents.c xkb: Free the XKB resource when freeing XkbInterest 2025-10-28 14:15:35 +01:00
xkbfmisc.c Drop trailing whitespaces 2014-11-12 10:25:00 +10:00
XKBGAlloc.c xkb: Fix heap overflow caused by optimized away min. 2020-12-04 18:31:06 -05:00
xkbgeom.h Drop trailing whitespaces 2014-11-12 10:25:00 +10:00
xkbInit.c xkb: Write the _XKB_RULES_NAMES window property synchronously 2018-11-13 10:36:18 -05:00
xkbLEDs.c xkb: after changing the keymap, force an indicator update 2016-05-04 10:55:09 -04:00
XKBMAlloc.c xkb: Check that needed is > 0 in XkbResizeKeyActions 2025-04-08 09:50:36 +02:00
XKBMisc.c xkb: Fix buffer overflow in XkbChangeTypesOfKey() 2025-02-25 19:36:29 +01:00
xkbout.c Drop trailing whitespaces 2014-11-12 10:25:00 +10:00
xkbPrKeyEv.c xkb: Match key releases with an overlaid press 2017-01-04 13:23:31 +10:00
xkbSwap.c Fix XkbSelectEvents() integer underflow 2020-08-25 17:01:29 +02:00
xkbtext.c xkb: Add tbGetBufferString helper function 2025-04-08 09:55:19 +02:00
xkbUtils.c xkb: Fix key type without level names in XkbCopyKeymap 2026-03-28 16:40:00 +00:00
XKM_file_format.txt Fix spelling/wording issues 2020-07-05 13:07:33 -07:00
xkmread.c xkb: Fix parsing of XkbSA_DeviceValuator action type 2021-03-30 18:47:04 +00:00

The X server uses this directory to store the compiled version of the
current keymap and/or any scratch keymaps used by clients.  The X server
or some other tool might destroy or replace the files in this directory,
so it is not a safe place to store compiled keymaps for long periods of
time.  The default keymap for any server is usually stored in:
     X<num>-default.xkm
where <num> is the display number of the server in question, which makes
it possible for several servers *on the same host* to share the same 
directory.

Unless the X server is modified, sharing this directory between servers on
different hosts could cause problems.