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Fix websocket crash from connection pointer dangling (#530)

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* websocket: Add dangling-prevent anchor pointer

* websocket: Fix deadlock from incorrect expiration expectation

* webscoket: Fix unsafe write access to anchor_

* websocket: Fix build error from use of 'nullptr_t'

* websocket: Remove latent dereferencing on dangling 'this' pointer

* websocket: Resolve conflict with master branch

Co-authored-by: Vladislav <vladislav.oleshko@gmail.com>
This commit is contained in:
Seungwoo Kang 2022-10-10 01:03:52 +09:00 committed by GitHub
parent f5adec7803
commit ac757ff0c9
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 44 additions and 4 deletions
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48
include/crow/websocket.h
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@ -118,18 +118,51 @@ namespace crow
start(crow::utility::base64encode((unsigned char*)digest, 20));
}
~Connection() noexcept override
{
// Do not modify anchor_ here since writing shared_ptr is not atomic.
auto watch = std::weak_ptr<void>{anchor_};
// Wait until all unhandled asynchronous operations to join.
// As the deletion occurs inside 'check_destroy()', which already locks
// anchor, use count can be 1 on valid deletion context.
while (watch.use_count() > 2) // 1 for 'check_destroy() routine', 1 for 'this->anchor_'
{
std::this_thread::yield();
}
}
template<typename Callable>
struct WeakWrappedMessage
{
Callable callable;
std::weak_ptr<void> watch;
void operator()()
{
if (auto anchor = watch.lock())
{
std::move(callable)();
}
}
};
/// Send data through the socket.
template<typename CompletionHandler>
void dispatch(CompletionHandler&& handler)
{
asio::dispatch(adaptor_.get_io_service(), std::forward<CompletionHandler>(handler));
asio::dispatch(adaptor_.get_io_service(),
WeakWrappedMessage<typename std::decay<CompletionHandler>::type>{
std::forward<CompletionHandler>(handler), anchor_});
}
/// Send data through the socket and return immediately.
template<typename CompletionHandler>
void post(CompletionHandler&& handler)
{
asio::post(adaptor_.get_io_service(), std::forward<CompletionHandler>(handler));
asio::post(adaptor_.get_io_service(),
WeakWrappedMessage<typename std::decay<CompletionHandler>::type>{
std::forward<CompletionHandler>(handler), anchor_});
}
/// Send a "Ping" message.
@ -605,12 +638,13 @@ namespace crow
{
buffers.emplace_back(asio::buffer(s));
}
auto watch = std::weak_ptr<void>{anchor_};
asio::async_write(
adaptor_.socket(), buffers,
[&](const asio::error_code& ec, std::size_t /*bytes_transferred*/) {
sending_buffers_.clear();
[&, watch](const asio::error_code& ec, std::size_t /*bytes_transferred*/) {
if (!ec && !close_connection_)
{
sending_buffers_.clear();
if (!write_buffers_.empty())
do_write();
if (has_sent_close_)
@ -618,6 +652,10 @@ namespace crow
}
else
{
auto anchor = watch.lock();
if (anchor == nullptr) { return; }
sending_buffers_.clear();
close_connection_ = true;
check_destroy();
}
@ -694,6 +732,8 @@ namespace crow
bool pong_received_{false};
bool is_close_handler_called_{false};
std::shared_ptr<void> anchor_ = std::make_shared<int>(); // Value is just for placeholding
std::function<void(crow::websocket::connection&)> open_handler_;
std::function<void(crow::websocket::connection&, const std::string&, bool)> message_handler_;
std::function<void(crow::websocket::connection&, const std::string&)> close_handler_;