[Bug 52401] Improper synchronization in sock_recv/sock_send leads to arbitrary reordering of completion of I/O requests

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=52401

--- Comment #1 from Jinoh Kang <jinoh.kang.kr at gmail.com> ---
I forgot that special (kernel) APCs can be delivered at any time.

In this case, steps 7 - 9 of the scenario are slightly modified:

1. The socket's incoming buffer is initially empty.

2. Client: The application calls WSARecv(). In sock_recv(), try_recv() fails
    with STATUS_DEVICE_NOT_READY; therefore, a deferred Async is queued to the
    server. WSARecv() returns with ERROR_IO_PENDING.

3. The socket receives packet [A] in the meantime. The socket's incoming buffer
    is no longer empty.

4. Client: The application calls WSARecv() again. In sock_recv(), try_recv()
    succeeds with packet [A]; therefore, an eager Async is queued to the
server.

5. The socket receives packet [B] in the meantime.

6. Server: the poll() loop detects this, and calls async_wake_up(
&sock->read_q,
    status ). This causes APC_ASYNC_IO for the deferred Async to be delivered
to
    the client process.

7. Client (SIGUSR1 handler): The client does a server select call. This returns
    STATUS_KERNEL_APC with APC_ASYNC_IO. The client calls try_recv() (from
    async_recv_proc), which succeeds with packet [B]. The client process
    completes the deferred Async with this packet.

8. Server: the wait on the async wait handle is satisfied, causing
    async_satisified() to be called. This in turn calls async_set_result(),
    which completes the eager Async (with packet [A]).

9. Client: The client exits sock_recv() and in turn WSARecv(), which reports
    immediate success.

It appears that my previously suggested solutions 2 and 3 would be
useless in this case.  Perhaps block any system APCs in the meantime?

If that's undesirable, we're left with solution #1.  That shouldn't be
too bad though, since the round trip to the server is inevitable anyway.
Perhaps we can optimize this path at the server side (instead of doing
eager/deferred processing in the user side).

--

Known impacted application: KakaoTalk 3.3.6.2992
(https://appdb.winehq.org/objectManager.php?sClass=version&iId=40551)

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