Re: [PATCH v2 1/3] win32: add qemu_close_socket_osfhandle()

[Daniel P . Berrangé]

On Mon, Mar 20, 2023 at 05:36:41PM +0400, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Close the given file descriptor, but returns the underlying SOCKET.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  include/sysemu/os-win32.h | 15 ++++++--
>  util/oslib-win32.c        | 75 +++++++++++++++++++++------------------
>  2 files changed, 53 insertions(+), 37 deletions(-)
> 
> diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h
> index e2849f88ab..15c296e0eb 100644
> --- a/include/sysemu/os-win32.h
> +++ b/include/sysemu/os-win32.h
> @@ -171,10 +171,21 @@ bool qemu_socket_select(int sockfd, WSAEVENT 
> hEventObject,
>  
>  bool qemu_socket_unselect(int sockfd, Error **errp);
>  
> -/* We wrap all the sockets functions so that we can
> - * set errno based on WSAGetLastError()
> +/* We wrap all the sockets functions so that we can set errno based on
> + * WSAGetLastError(), and use file-descriptors instead of SOCKET.
>   */
>  
> +/*
> + * qemu_close_socket_osfhandle:
> + * @fd: a file descriptor associated with a SOCKET
> + *
> + * Close only the C run-time file descriptor, leave the SOCKET opened.
> + *
> + * Returns zero on success. On error, -1 is returned, and errno is set to
> + * indicate the error.
> + */
> +int qemu_close_socket_osfhandle(int fd);
> +
>  #undef close
>  #define close qemu_close_wrap
>  int qemu_close_wrap(int fd);
> diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> index 16f8a67f7e..a98638729a 100644
> --- a/util/oslib-win32.c
> +++ b/util/oslib-win32.c
> @@ -479,40 +479,27 @@ int qemu_bind_wrap(int sockfd, const struct sockaddr 
> *addr,
>      return ret;
>  }
>  
> -
>  #undef close
> -int qemu_close_wrap(int fd)
> +int qemu_close_socket_osfhandle(int fd)
>  {
> -    int ret;
> +    SOCKET s = _get_osfhandle(fd);
>      DWORD flags = 0;
> -    SOCKET s = INVALID_SOCKET;
> -
> -    if (fd_is_socket(fd)) {
> -        s = _get_osfhandle(fd);
> -
> -        /*
> -         * If we were to just call _close on the descriptor, it would close 
> the
> -         * HANDLE, but it wouldn't free any of the resources associated to 
> the
> -         * SOCKET, and we can't call _close after calling closesocket, 
> because
> -         * closesocket has already closed the HANDLE, and _close would 
> attempt to
> -         * close the HANDLE again, resulting in a double free. We can however
> -         * protect the HANDLE from actually being closed long enough to 
> close the
> -         * file descriptor, then close the socket itself.
> -         */
> -        if (!GetHandleInformation((HANDLE)s, &flags)) {
> -            errno = EACCES;
> -            return -1;
> -        }
>  
> -        if (!SetHandleInformation((HANDLE)s, HANDLE_FLAG_PROTECT_FROM_CLOSE, 
> HANDLE_FLAG_PROTECT_FROM_CLOSE)) {
> -            errno = EACCES;
> -            return -1;
> -        }
> +    /*
> +     * If we were to just call _close on the descriptor, it would close the
> +     * HANDLE, but it wouldn't free any of the resources associated to the
> +     * SOCKET, and we can't call _close after calling closesocket, because
> +     * closesocket has already closed the HANDLE, and _close would attempt to
> +     * close the HANDLE again, resulting in a double free. We can however
> +     * protect the HANDLE from actually being closed long enough to close the
> +     * file descriptor, then close the socket itself.
> +     */
> +    if (!GetHandleInformation((HANDLE)s, &flags)) {
> +        errno = EACCES;
> +        return -1;
>      }
>  
> -    ret = close(fd);
> -
> -    if (s != INVALID_SOCKET && !SetHandleInformation((HANDLE)s, flags, 
> flags)) {
> +    if (!SetHandleInformation((HANDLE)s, HANDLE_FLAG_PROTECT_FROM_CLOSE, 
> HANDLE_FLAG_PROTECT_FROM_CLOSE)) {
>          errno = EACCES;
>          return -1;
>      }
> @@ -521,15 +508,33 @@ int qemu_close_wrap(int fd)
>       * close() returns EBADF since we PROTECT_FROM_CLOSE the underlying 
> handle,
>       * but the FD is actually freed
>       */
> -    if (ret < 0 && (s == INVALID_SOCKET || errno != EBADF)) {
> -        return ret;
> +    if (close(fd) < 0 && errno != EBADF) {
> +        return -1;
>      }
>  
> -    if (s != INVALID_SOCKET) {
> -        ret = closesocket(s);
> -        if (ret < 0) {
> -            errno = socket_error();
> -        }
> +    if (!SetHandleInformation((HANDLE)s, flags, flags)) {
> +        errno = EACCES;
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +int qemu_close_wrap(int fd)
> +{
> +    SOCKET s = INVALID_SOCKET;
> +    int ret = -1;
> +
> +    if (!fd_is_socket(fd)) {
> +        return close(fd);
> +    }
> +
> +    s = _get_osfhandle(fd);
> +    qemu_close_socket_osfhandle(fd);
> +
> +    ret = closesocket(s);
> +    if (ret < 0) {
> +        errno = socket_error();
>      }

Shouldn't the closesocket() and return check be wrapped in

   if (s != INVALID_SOCKET) { .... }

as the old code had that conditional invokation of closesocket() ?

With regards,
Daniel
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