netdev - Re: [PATCH net] rds: Incorrect reference counting in TCP socket creation

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Message-ID: <CACP96tRwyR36oduAJYYVXRPTW92NK4Ac5xv6cB_u8PX5RYcdww@mail.gmail.com>
Date:   Thu, 1 Mar 2018 06:54:13 -0500
From:   Sowmini Varadhan <sowmini05@...il.com>
To:     Ka-Cheong Poon <ka-cheong.poon@...cle.com>
Cc:     netdev <netdev@...r.kernel.org>, santosh.shilimkar@...cle.com,
        David Miller <davem@...emloft.net>, rds-devel@....oracle.com,
        Sowmini Varadhan <sowmini.varadhan@...cle.com>
Subject: Re: [PATCH net] rds: Incorrect reference counting in TCP socket creation

On Wed, Feb 28, 2018 at 11:44 PM, Ka-Cheong Poon
<ka-cheong.poon@...cle.com> wrote:
> Commit 0933a578cd55 ("rds: tcp: use sock_create_lite() to create the
> accept socket") has a reference counting issue in TCP socket creation
> when accepting a new connection.  The code uses sock_create_lite() to
> create a kernel socket.  But it does not do __module_get() on the
> socket owner.  When the connection is shutdown and sock_release() is
> called to free the socket, the owner's reference count is decremented
> and becomes incorrect.  Note that this bug only shows up when the socket
> owner is configured as a kernel module.

>
> -       new_sock->type = sock->type;
> -       new_sock->ops = sock->ops;
>         ret = sock->ops->accept(sock, new_sock, O_NONBLOCK, true);
>         if (ret < 0)
>                 goto out;
>
> +       new_sock->ops = sock->ops;

How is this delta relevant to the commit comment? Seems unrelated?

--Sowmini