linux-kernel - Re: [PATCH v2 1/3] vsock/virtio: use RCU to avoid use-after-free on the_virtio

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Message-ID: <20190701151008.GD11900@stefanha-x1.localdomain>
Date:   Mon, 1 Jul 2019 16:10:08 +0100
From:   Stefan Hajnoczi <stefanha@...il.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     netdev@...r.kernel.org, kvm@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v2 1/3] vsock/virtio: use RCU to avoid use-after-free on
 the_virtio_vsock

On Fri, Jun 28, 2019 at 02:36:57PM +0200, Stefano Garzarella wrote:
> Some callbacks used by the upper layers can run while we are in the
> .remove(). A potential use-after-free can happen, because we free
> the_virtio_vsock without knowing if the callbacks are over or not.
> 
> To solve this issue we move the assignment of the_virtio_vsock at the
> end of .probe(), when we finished all the initialization, and at the
> beginning of .remove(), before to release resources.
> For the same reason, we do the same also for the vdev->priv.
> 
> We use RCU to be sure that all callbacks that use the_virtio_vsock
> ended before freeing it. This is not required for callbacks that
> use vdev->priv, because after the vdev->config->del_vqs() we are sure
> that they are ended and will no longer be invoked.

My question is answered in Patch 3.

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