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Subject: Re: [PATCH v2 1/3] vsock/virtio: use RCU to avoid use-after-free on
 the_virtio_vsock
To:     Stefano Garzarella <sgarzare@redhat.com>
Cc:     Stefan Hajnoczi <stefanha@redhat.com>, netdev@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        "Michael S. Tsirkin" <mst@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        linux-kernel@vger.kernel.org
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 <20190703104135.wg34dobv64k7u4jo@steredhat>
 <07e5bc00-ebde-4dac-d38c-f008fa230b5f@redhat.com>
 <20190704092044.23gd5o2rhqarisgg@steredhat.homenet.telecomitalia.it>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <23c014de-90b5-1de2-a118-63ec242cbf62@redhat.com>
Date:   Fri, 5 Jul 2019 08:18:37 +0800
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On 2019/7/4 下午5:20, Stefano Garzarella wrote:
>>>> This is still suspicious, can we access the_virtio_vsock through vdev->priv?
>>>> If yes, we may still get use-after-free since it was not protected by RCU.
>>> We will free the object only after calling the del_vqs(), so we are sure
>>> that the vq_callbacks ended and will no longer be invoked.
>>> So, IIUC it shouldn't happen.
>> Yes, but any dereference that is not done in vq_callbacks will be very
>> dangerous in the future.
> Right.
>
> Do you think make sense to continue with this series in order to fix the
> hot-unplug issue, then I'll work to refactor the driver code to use the refcnt
> (as you suggested in patch 2) and singleton for the_virtio_vsock?
>
> Thanks,
> Stefano


Yes.

Thanks