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authorPeter Hutterer <peter.hutterer@who-t.net>2022-11-29 12:55:45 +1000
committerPeter Hutterer <peter.hutterer@who-t.net>2022-12-12 10:55:49 +1000
commitb320ca0ffe4c0c872eeb3a93d9bde21f765c7c63 (patch)
treeb89877cdcd0ddf4498fc699ecf89d7d50f01f804
parent4781f2a5a8c2c2b000374e2d87982a6701d5a6b3 (diff)
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. CVE-2022-46340, 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> Acked-by: Olivier Fourdan <ofourdan@redhat.com>
-rw-r--r--Xext/xtest.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/Xext/xtest.c b/Xext/xtest.c
index bf27eb590..2985a4ce6 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;
}