File U_0001-Xtest-disallow-GenericEvents-in-XTestSwa... of Package xorg-x11-server

Overview Repositories Revisions Requests Users Attributes Meta

File U_0001-Xtest-disallow-GenericEvents-in-XTestSwapFakeInput.patch of Package xorg-x11-server (Revision ca3f42c99a52fcc9a00b800572c58ea1)

Currently displaying revision ca3f42c99a52fcc9a00b800572c58ea1 , Show latest

From 2e8916efe9a8566f97a4c2231891ad0f555fced1 Mon Sep 17 00:00:00 2001
From: Peter Hutterer <peter.hutterer@who-t.net>
Date: Tue, 29 Nov 2022 12:55:45 +1000
Subject: [PATCH xserver 1/6] Xtest: disallow GenericEvents in
 XTestSwapFakeInput

XTestSwapFakeInput assumes all events in this request are
sizeof(xEvent) and iterates through these in 32-byte increments.
However, a GenericEvent may be of arbitrary length longer than 32 bytes,
so any GenericEvent in this list would result in subsequent events to be
misparsed.

Additional, the swapped event is written into a stack-allocated struct
xEvent (size 32 bytes). For any GenericEvent longer than 32 bytes,
swapping the event may thus smash the stack like an avocado on toast.

Catch this case early and return BadValue for any GenericEvent.
Which is what would happen in unswapped setups anyway since XTest
doesn't support GenericEvent.

ZDI-CAN 19265

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

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
---
 Xext/xtest.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Xext/xtest.c b/Xext/xtest.c
index bf27eb590b..2985a4ce6e 100644
--- a/Xext/xtest.c
+++ b/Xext/xtest.c
@@ -502,10 +502,11 @@ XTestSwapFakeInput(ClientPtr client, xReq * req)
 
     nev = ((req->length << 2) - sizeof(xReq)) / sizeof(xEvent);
     for (ev = (xEvent *) &req[1]; --nev >= 0; ev++) {
+        int evtype = ev->u.u.type & 0x177;
         /* Swap event */
-        proc = EventSwapVector[ev->u.u.type & 0177];
+        proc = EventSwapVector[evtype];
         /* no swapping proc; invalid event type? */
-        if (!proc || proc == NotImplemented) {
+        if (!proc || proc == NotImplemented || evtype == GenericEvent) {
             client->errorValue = ev->u.u.type;
             return BadValue;
         }
-- 
2.38.1

Places

File U_0001-Xtest-disallow-GenericEvents-in-XTestSwapFakeInput.patch of Package xorg-x11-server (Revision ca3f42c99a52fcc9a00b800572c58ea1)

Places