Re: [Qemu-devel] [PATCH] Delete AF_UNIX socket after close

["Daniel P. Berrangé" <berrange@redhat.com>]

On Mon, May 21, 2018 at 02:10:18PM +0300, Pavel Balaev wrote:
> Hello,
> 
> Since version 2.12.0 AF_UNIX socket created for QMP exchange is not
> deleted on instance shutdown.
> 
> This is due to the fact that function qio_channel_socket_finalize() is
> called after qio_channel_socket_close().

Hmm, finalize() has always been called as the last thing on the
object. I wonder if the problem was that previously we simply
never called close() at all, in some case and relied on finalize
closing the socket ?

Either way the current code was clearly broken

> Signed-off-by: Pavel Balaev <mail@void.so>
> ---
>  include/qemu/sockets.h |  1 -
>  io/channel-socket.c    | 40 +++++++++++++++-------------------------
>  util/qemu-sockets.c    | 21 ---------------------
>  3 files changed, 15 insertions(+), 47 deletions(-)
> 
> diff --git a/include/qemu/sockets.h b/include/qemu/sockets.h
> index 8140fea685..a786bd76d7 100644
> --- a/include/qemu/sockets.h
> +++ b/include/qemu/sockets.h
> @@ -42,7 +42,6 @@ int unix_connect(const char *path, Error **errp);
>  SocketAddress *socket_parse(const char *str, Error **errp);
>  int socket_connect(SocketAddress *addr, Error **errp);
>  int socket_listen(SocketAddress *addr, Error **errp);
> -void socket_listen_cleanup(int fd, Error **errp);
>  int socket_dgram(SocketAddress *remote, SocketAddress *local, Error **errp);
>  
>  /* Old, ipv4 only bits.  Don't use for new code. */
> diff --git a/io/channel-socket.c b/io/channel-socket.c
> index 57cfb4d3a6..3c88ca4130 100644
> --- a/io/channel-socket.c
> +++ b/io/channel-socket.c
> @@ -383,30 +383,6 @@ static void qio_channel_socket_init(Object *obj)
>      ioc->fd = -1;
>  }
>  
> -static void qio_channel_socket_finalize(Object *obj)
> -{
> -    QIOChannelSocket *ioc = QIO_CHANNEL_SOCKET(obj);
> -
> -    if (ioc->fd != -1) {
> -        QIOChannel *ioc_local = QIO_CHANNEL(ioc);
> -        if (qio_channel_has_feature(ioc_local, QIO_CHANNEL_FEATURE_LISTEN)) {
> -            Error *err = NULL;
> -
> -            socket_listen_cleanup(ioc->fd, &err);
> -            if (err) {
> -                error_report_err(err);
> -                err = NULL;
> -            }
> -        }
> -#ifdef WIN32
> -        WSAEventSelect(ioc->fd, NULL, 0);
> -#endif
> -        closesocket(ioc->fd);
> -        ioc->fd = -1;
> -    }
> -}

This is not right - we can't assume that the owner has definitely
called close().  Some codepaths might call it, others might not.
So we must have a finalize method that cleans up.

> -
> -
>  #ifndef WIN32
>  static void qio_channel_socket_copy_fds(struct msghdr *msg,
>                                          int **fds, size_t *nfds)
> @@ -687,6 +663,8 @@ qio_channel_socket_close(QIOChannel *ioc,
>      QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc);
>  
>      if (sioc->fd != -1) {
> +        SocketAddress *addr = socket_local_address(sioc->fd, errp);
> +
>  #ifdef WIN32
>          WSAEventSelect(sioc->fd, NULL, 0);
>  #endif
> @@ -697,6 +675,19 @@ qio_channel_socket_close(QIOChannel *ioc,
>              return -1;
>          }
>          sioc->fd = -1;
> +
> +        if (addr && addr->type == SOCKET_ADDRESS_TYPE_UNIX
> +            && addr->u.q_unix.path) {
> +            if (unlink(addr->u.q_unix.path) < 0 && errno != ENOENT) {
> +                error_setg_errno(errp, errno,
> +                                 "Failed to unlink socket %s",
> +                                 addr->u.q_unix.path);
> +            }
> +        }
> +
> +        if (addr) {
> +            qapi_free_SocketAddress(addr);
> +        }

This bit is good though.

>      }
>      return 0;
>  }
> @@ -770,7 +761,6 @@ static const TypeInfo qio_channel_socket_info = {
>      .name = TYPE_QIO_CHANNEL_SOCKET,
>      .instance_size = sizeof(QIOChannelSocket),
>      .instance_init = qio_channel_socket_init,
> -    .instance_finalize = qio_channel_socket_finalize,
>      .class_init = qio_channel_socket_class_init,
>  };
>  
> diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
> index 8bd8bb64eb..aedcb5b9c0 100644
> --- a/util/qemu-sockets.c
> +++ b/util/qemu-sockets.c
> @@ -1120,27 +1120,6 @@ int socket_listen(SocketAddress *addr, Error **errp)
>      return fd;
>  }
>  
> -void socket_listen_cleanup(int fd, Error **errp)
> -{
> -    SocketAddress *addr;
> -
> -    addr = socket_local_address(fd, errp);
> -    if (!addr) {
> -        return;
> -    }
> -
> -    if (addr->type == SOCKET_ADDRESS_TYPE_UNIX
> -        && addr->u.q_unix.path) {
> -        if (unlink(addr->u.q_unix.path) < 0 && errno != ENOENT) {
> -            error_setg_errno(errp, errno,
> -                             "Failed to unlink socket %s",
> -                             addr->u.q_unix.path);
> -        }
> -    }
> -
> -    qapi_free_SocketAddress(addr);
> -}
> -
>  int socket_dgram(SocketAddress *remote, SocketAddress *local, Error **errp)
>  {
>      int fd;
> -- 
> 2.16.1
> 
> 

Regards,
Daniel
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