From 45daaa0cb895d8e01f34b3138316bcb83bb7a845 Mon Sep 17 00:00:00 2001
From: Kramer Ge <fangzhoug@chromium.org>
Date: Thu, 18 Jun 2026 08:11:54 -0700
Subject: [PATCH] [Ozone/Wayland]Fix Use-After-Free in OnPointerFrameEvent

In WaylandEventSource::OnPointerFrameEvent, a raw pointer to the
focused WaylandWindow was cached outside the loop that drains
pointer_frames_. If the window is synchronously closed during event
dispatch, subsequent events in the same frame would use the dangling
pointer, leading to a Use-After-Free.

This CL fixes the issue by caching the target window as a WeakPtr
and verifying its validity before each event dispatch.

BUG=523725277
TAG=agy
CONV=600e2394-2a5e-4d13-93b9-91470f489eeb

Change-Id: I8cd33570342fc1592ef5f78c5a2ec72064af1ea7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7958261
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Kramer Ge <fangzhoug@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1649050}
---

diff --git a/ui/ozone/platform/wayland/host/wayland_event_source.cc b/ui/ozone/platform/wayland/host/wayland_event_source.cc
index 5e70540..6f4238a 100644
--- a/ui/ozone/platform/wayland/host/wayland_event_source.cc
+++ b/ui/ozone/platform/wayland/host/wayland_event_source.cc
@@ -550,17 +550,22 @@
 
   last_pointer_frame_time_ = now;
 
-  auto* target = window_manager_->GetCurrentPointerFocusedWindow();
-  if (!target) {
+  auto* target_window = window_manager_->GetCurrentPointerFocusedWindow();
+  if (!target_window) {
     return;
   }
+  // Dispatching an event may synchronously destroy the focused window (e.g. a
+  // popup closing on click), so hold a WeakPtr and re-check on each iteration.
+  base::WeakPtr<WaylandWindow> target = target_window->AsWeakPtr();
 
   while (!pointer_frames_.empty()) {
     // It is safe to pop the first queued event for processing.
     auto pointer_frame = std::move(pointer_frames_.front());
     pointer_frames_.pop_front();
 
-    SetTargetAndDispatchEvent(pointer_frame->event.get(), target);
+    if (target) {
+      SetTargetAndDispatchEvent(pointer_frame->event.get(), target.get());
+    }
     if (!pointer_frame->completion_cb.is_null()) {
       std::move(pointer_frame->completion_cb).Run();
     }
@@ -739,6 +744,7 @@
 
 void WaylandEventSource::SetTargetAndDispatchEvent(Event* event,
                                                    EventTarget* target) {
+  CHECK(target);
   Event::DispatcherApi(event).set_target(target);
   if (event->IsLocatedEvent()) {
     auto* located_event = event->AsLocatedEvent();
diff --git a/ui/ozone/platform/wayland/host/wayland_pointer_unittest.cc b/ui/ozone/platform/wayland/host/wayland_pointer_unittest.cc
index 7e2cd4a7..26d87aa5 100644
--- a/ui/ozone/platform/wayland/host/wayland_pointer_unittest.cc
+++ b/ui/ozone/platform/wayland/host/wayland_pointer_unittest.cc
@@ -721,6 +721,41 @@
   EXPECT_EQ(0.0f, scroll_event->y_offset_ordinal());
 }
 
+TEST_F(WaylandPointerTest, FrameTargetUseAfterFreeOnSyncWindowClose) {
+  SendEnter(50, 50);
+
+  // Frame 1: axis_stop -> FlingStart is queued and drained (1 event). This
+  // sets is_fling_active_=true so the next finger-scroll frame will queue 2
+  // events (FlingCancel + Scroll).
+  SendAxisStopEvents();
+
+  // Simulate a popup widget closing from inside its own event handler.
+  bool destroyed = false;
+  EXPECT_CALL(delegate_, DispatchEvent(_))
+      .WillRepeatedly([this, &destroyed](Event* event) {
+        if (!destroyed) {
+          destroyed = true;
+          window_.reset();
+        }
+      });
+
+  // Frame 2: finger axis -> ProcessPointerScrollData() pushes 2 events
+  // [FlingCancel, Scroll] into pointer_frames_, then OnPointerFrameEvent()
+  // drains both against the cached `target`. The first dispatch frees
+  // `target`; the second dispatch should be dismissed.
+  PostToServerAndWait([](wl::TestWaylandServerThread* server) {
+    auto* const pointer = server->seat()->pointer()->resource();
+    SendAxisEvents(pointer, server->GetNextTime(),
+                   WL_POINTER_AXIS_SOURCE_FINGER,
+                   WL_POINTER_AXIS_VERTICAL_SCROLL, 10);
+  });
+
+  EXPECT_TRUE(destroyed);
+
+  // The test fixture's window has been torn down mid-test.
+  DisableSyncOnTearDown();
+}
+
 TEST_F(WaylandPointerTest, FlingVelocityWithSingleLeadingAxis) {
   SendEnter(50, 75);
 

diff --git a/ui/ozone/platform/wayland/host/wayland_pointer_unittest.cc b/ui/ozone/platform/wayland/host/wayland_pointer_unittest.cc
index 7e2cd4a7..26d87aa5 100644
--- a/ui/ozone/platform/wayland/host/wayland_pointer_unittest.cc
+++ b/ui/ozone/platform/wayland/host/wayland_pointer_unittest.cc
@@ -721,6 +721,41 @@
   EXPECT_EQ(0.0f, scroll_event->y_offset_ordinal());
 }
 
+TEST_F(WaylandPointerTest, FrameTargetUseAfterFreeOnSyncWindowClose) {
+  SendEnter(50, 50);
+
+  // Frame 1: axis_stop -> FlingStart is queued and drained (1 event). This
+  // sets is_fling_active_=true so the next finger-scroll frame will queue 2
+  // events (FlingCancel + Scroll).
+  SendAxisStopEvents();
+
+  // Simulate a popup widget closing from inside its own event handler.
+  bool destroyed = false;
+  EXPECT_CALL(delegate_, DispatchEvent(_))
+      .WillRepeatedly([this, &destroyed](Event* event) {
+        if (!destroyed) {
+          destroyed = true;
+          window_.reset();
+        }
+      });
+
+  // Frame 2: finger axis -> ProcessPointerScrollData() pushes 2 events
+  // [FlingCancel, Scroll] into pointer_frames_, then OnPointerFrameEvent()
+  // drains both against the cached `target`. The first dispatch frees
+  // `target`; the second dispatch should be dismissed.
+  PostToServerAndWait([](wl::TestWaylandServerThread* server) {
+    auto* const pointer = server->seat()->pointer()->resource();
+    SendAxisEvents(pointer, server->GetNextTime(),
+                   WL_POINTER_AXIS_SOURCE_FINGER,
+                   WL_POINTER_AXIS_VERTICAL_SCROLL, 10);
+  });
+
+  EXPECT_TRUE(destroyed);
+
+  // The test fixture's window has been torn down mid-test.
+  DisableSyncOnTearDown();
+}
+
 TEST_F(WaylandPointerTest, FlingVelocityWithSingleLeadingAxis) {
   SendEnter(50, 75);