From ad318128f5e2276cd8dcb1d3de516d657b05ff7d Mon Sep 17 00:00:00 2001
From: Alexander Aprelev <aam@google.com>
Date: Wed, 1 Oct 2025 15:15:20 -0700
Subject: [PATCH] [io] Fix race between closing socket and requesting its type.

Fixes https://github.com/dart-lang/sdk/issues/61582

Revert "[io/socket] Make Socket::fd_ atomic since it can get updated from multiple threads."
Revert "[gardening] Fix fuchsia build - assign atomic to intptr_t before reinterpret_cast to pointer."

TEST=ci

Change-Id: Ia755d6623e46b7940800a12bf4a5d8d9cb674522
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/451822
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Alexander Aprelev <aam@google.com>
---
 runtime/bin/socket.cc                     | 5 +++++
 runtime/bin/socket.h                      | 2 +-
 runtime/bin/socket_base_win.cc            | 4 ----
 runtime/bin/socket_fuchsia.cc             | 5 ++---
 runtime/bin/socket_win.cc                 | 8 +++-----
 sdk/lib/_internal/vm/bin/stdio_patch.dart | 6 ++++++
 6 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/runtime/bin/socket.cc b/runtime/bin/socket.cc
index 0de173f2b70..1d14d428468 100644
--- a/runtime/bin/socket.cc
+++ b/runtime/bin/socket.cc
@@ -953,6 +953,11 @@ void FUNCTION_NAME(Socket_GetFD)(Dart_NativeArguments args) {
 void FUNCTION_NAME(Socket_GetType)(Dart_NativeArguments args) {
   Socket* socket =
       Socket::GetSocketIdNativeField(Dart_GetNativeArgument(args, 0));
+  if (socket->fd() < 0) {
+    OSError os_error(-1, "Socket is closed.", OSError::kUnknown);
+    Dart_SetReturnValue(args, DartUtils::NewDartOSError(&os_error));
+    return;
+  }
   OSError os_error;
   intptr_t type = SocketBase::GetType(socket->fd());
   if (type >= 0) {
diff --git a/runtime/bin/socket.h b/runtime/bin/socket.h
index a5a998ad237..9a53d51774d 100644
--- a/runtime/bin/socket.h
+++ b/runtime/bin/socket.h
@@ -124,7 +124,7 @@ class Socket : public ReferenceCounted<Socket> {
   static bool short_socket_read_;
   static bool short_socket_write_;
 
-  std::atomic<intptr_t> fd_;
+  intptr_t fd_;
   Dart_Port isolate_port_;
   Dart_Port port_;
   uint8_t* udp_receive_buffer_;
diff --git a/runtime/bin/socket_base_win.cc b/runtime/bin/socket_base_win.cc
index 25c40caf7d5..966dada4de8 100644
--- a/runtime/bin/socket_base_win.cc
+++ b/runtime/bin/socket_base_win.cc
@@ -215,10 +215,6 @@ void SocketBase::GetError(intptr_t fd, OSError* os_error) {
 }
 
 int SocketBase::GetType(intptr_t fd) {
-  if (fd < 0) {
-    return -1;
-  }
-
   Handle* handle = reinterpret_cast<Handle*>(fd);
   switch (GetFileType(handle->handle())) {
     case FILE_TYPE_CHAR:
diff --git a/runtime/bin/socket_fuchsia.cc b/runtime/bin/socket_fuchsia.cc
index 11093899a60..885ec97063d 100644
--- a/runtime/bin/socket_fuchsia.cc
+++ b/runtime/bin/socket_fuchsia.cc
@@ -55,9 +55,8 @@ void Socket::SetClosedFd() {
 }
 
 void Socket::CloseFd() {
-  intptr_t fd_handle = fd();
-  ASSERT(fd_handle != kClosedFd);
-  IOHandle* handle = reinterpret_cast<IOHandle*>(fd_handle);
+  ASSERT(fd_ != kClosedFd);
+  IOHandle* handle = reinterpret_cast<IOHandle*>(fd_);
   ASSERT(handle != nullptr);
   handle->Release();
   SetClosedFd();
diff --git a/runtime/bin/socket_win.cc b/runtime/bin/socket_win.cc
index fbb5bb6a3b6..a64dceeb390 100644
--- a/runtime/bin/socket_win.cc
+++ b/runtime/bin/socket_win.cc
@@ -26,15 +26,13 @@ Socket::Socket(intptr_t fd)
       port_(ILLEGAL_PORT),
       udp_receive_buffer_(nullptr) {
   ASSERT(fd_ != kClosedFd);
-  intptr_t fd_handle = fd_;
-  Handle* handle = reinterpret_cast<Handle*>(fd_handle);
+  Handle* handle = reinterpret_cast<Handle*>(fd_);
   ASSERT(handle != nullptr);
 }
 
 void Socket::CloseFd() {
-  intptr_t fd_handle = fd();
-  ASSERT(fd_handle != kClosedFd);
-  Handle* handle = reinterpret_cast<Handle*>(fd_handle);
+  ASSERT(fd_ != kClosedFd);
+  Handle* handle = reinterpret_cast<Handle*>(fd_);
   ASSERT(handle != nullptr);
   handle->Release();
   SetClosedFd();
diff --git a/sdk/lib/_internal/vm/bin/stdio_patch.dart b/sdk/lib/_internal/vm/bin/stdio_patch.dart
index e4074dfbf74..d97d5a03b92 100644
--- a/sdk/lib/_internal/vm/bin/stdio_patch.dart
+++ b/sdk/lib/_internal/vm/bin/stdio_patch.dart
@@ -48,6 +48,12 @@ class _StdIOUtils {
   }
 
   static int _nativeSocketType(_NativeSocket nativeSocket) {
+    if (nativeSocket.isClosed) {
+      throw FileSystemException("Socket is closed");
+    }
+    if (nativeSocket.isClosing) {
+      throw FileSystemException("Socket is being closed");
+    }
     var result = _getSocketType(nativeSocket);
     if (result is OSError) {
       throw FileSystemException("Error retrieving socket type", "", result);