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From 6e0f332ba4c8b8c9a9945dc9d7989bfe06f80e14 Mon Sep 17 00:00:00 2001
From: Olivier Fourdan <ofourdan@redhat.com>
Date: Mon, 16 Dec 2024 16:18:04 +0100
Subject: [PATCH] dix: Dequeue pending events on frozen device on removal
When a device is removed while still frozen, the events queued for that
device remain while the device itself is freed.
As a result, replaying the events will cause a use after free.
To avoid the issue, make sure to dequeue and free any pending events on
a frozen device when removed.
CVE-2025-26600, ZDI-CAN-25871
This vulnerability was discovered by:
Jan-Niklas Sohn working with Trend Micro Zero Day Initiative
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1828>
Upstream-Status: Backport [https://gitlab.freedesktop.org/xorg/xserver/-/commit/6e0f332b]
CVE: CVE-2025-26600
Signed-off-by: Vijay Anusuri <vanusuri@mvista.com>
---
dix/devices.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/dix/devices.c b/dix/devices.c
index 1516147..459f1ed 100644
--- a/dix/devices.c
+++ b/dix/devices.c
@@ -962,6 +962,23 @@ FreeAllDeviceClasses(ClassesPtr classes)
}
+static void
+FreePendingFrozenDeviceEvents(DeviceIntPtr dev)
+{
+ QdEventPtr qe, tmp;
+
+ if (!dev->deviceGrab.sync.frozen)
+ return;
+
+ /* Dequeue any frozen pending events */
+ xorg_list_for_each_entry_safe(qe, tmp, &syncEvents.pending, next) {
+ if (qe->device == dev) {
+ xorg_list_del(&qe->next);
+ free(qe);
+ }
+ }
+}
+
/**
* Close down a device and free all resources.
* Once closed down, the driver will probably not expect you that you'll ever
@@ -1026,6 +1043,7 @@ CloseDevice(DeviceIntPtr dev)
free(dev->last.touches[j].valuators);
free(dev->last.touches);
dev->config_info = NULL;
+ FreePendingFrozenDeviceEvents(dev);
dixFreePrivates(dev->devPrivates, PRIVATE_DEVICE);
free(dev);
}
--
2.25.1
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