From 313efed9c9dc95b610a4a933ba7faf487de1ea0f Mon Sep 17 00:00:00 2001
From: Francis Tsui <ftsui@google.com>
Date: Thu, 7 May 2026 22:17:02 -0700
Subject: [PATCH] Fix unprotected multi-threaded access to list.

PiperOrigin-RevId: 912324436
---
 internal/platform/implementation/windows/wifi_hotspot.h      | 2 +-
 .../platform/implementation/windows/wifi_hotspot_medium.cc   | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/internal/platform/implementation/windows/wifi_hotspot.h b/internal/platform/implementation/windows/wifi_hotspot.h
index c6b4c34a..b68926ec 100644
--- a/internal/platform/implementation/windows/wifi_hotspot.h
+++ b/internal/platform/implementation/windows/wifi_hotspot.h
@@ -111,7 +111,7 @@ class WifiHotspotMedium : public api::WifiHotspotMedium {
   WiFiDirectConnectionListener listener_{nullptr};
 
   // The list of WiFiDirectDevice is used to keep hotspot connection alive.
-  std::list<WiFiDirectDevice> wifi_direct_devices_;
+  std::list<WiFiDirectDevice> wifi_direct_devices_ ABSL_GUARDED_BY(mutex_);
 
   fire_and_forget OnStatusChanged(
       WiFiDirectAdvertisementPublisher sender,
diff --git a/internal/platform/implementation/windows/wifi_hotspot_medium.cc b/internal/platform/implementation/windows/wifi_hotspot_medium.cc
index 288efe14..e6ca86bd 100644
--- a/internal/platform/implementation/windows/wifi_hotspot_medium.cc
+++ b/internal/platform/implementation/windows/wifi_hotspot_medium.cc
@@ -349,7 +349,10 @@ fire_and_forget WifiHotspotMedium::OnConnectionRequested(
     auto wifi_direct_device = WiFiDirectDevice::FromIdAsync(
                                   connection_request.DeviceInformation().Id())
                                   .get();
-    wifi_direct_devices_.push_back(wifi_direct_device);
+    {
+      absl::MutexLock lock(mutex_);
+      wifi_direct_devices_.push_back(wifi_direct_device);
+    }
     LOG(INFO) << "Registered the device " << winrt::to_string(device_name)
               << " in WLAN-AutoConfig";
   } catch (...) {