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From b320ca0ffe4c0c872eeb3a93d9bde21f765c7c63 Mon Sep 17 00:00:00 2001
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From: Peter Hutterer <peter.hutterer@who-t.net>
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Date: Tue, 29 Nov 2022 12:55:45 +1000
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Subject: [PATCH xserver 1/7] Xtest: disallow GenericEvents in
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XTestSwapFakeInput
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XTestSwapFakeInput assumes all events in this request are
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sizeof(xEvent) and iterates through these in 32-byte increments.
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However, a GenericEvent may be of arbitrary length longer than 32 bytes,
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so any GenericEvent in this list would result in subsequent events to be
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misparsed.
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Additional, the swapped event is written into a stack-allocated struct
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xEvent (size 32 bytes). For any GenericEvent longer than 32 bytes,
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swapping the event may thus smash the stack like an avocado on toast.
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Catch this case early and return BadValue for any GenericEvent.
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Which is what would happen in unswapped setups anyway since XTest
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doesn't support GenericEvent.
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CVE-2022-46340, ZDI-CAN 19265
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This vulnerability was discovered by:
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Jan-Niklas Sohn working with Trend Micro Zero Day Initiative
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Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
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Acked-by: Olivier Fourdan <ofourdan@redhat.com>
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---
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Xext/xtest.c | 5 +++--
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1 file changed, 3 insertions(+), 2 deletions(-)
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diff --git a/Xext/xtest.c b/Xext/xtest.c
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index bf27eb590b..2985a4ce6e 100644
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--- a/Xext/xtest.c
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+++ b/Xext/xtest.c
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@@ -502,10 +502,11 @@ XTestSwapFakeInput(ClientPtr client, xReq * req)
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nev = ((req->length << 2) - sizeof(xReq)) / sizeof(xEvent);
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for (ev = (xEvent *) &req[1]; --nev >= 0; ev++) {
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+ int evtype = ev->u.u.type & 0x177;
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/* Swap event */
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- proc = EventSwapVector[ev->u.u.type & 0177];
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+ proc = EventSwapVector[evtype];
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/* no swapping proc; invalid event type? */
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- if (!proc || proc == NotImplemented) {
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+ if (!proc || proc == NotImplemented || evtype == GenericEvent) {
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client->errorValue = ev->u.u.type;
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return BadValue;
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}
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--
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2.38.1
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