netdev - Re: [PATCH v2] vsock/virtio: initialize the_virtio

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Date: Mon, 23 Oct 2023 17:52:03 +0300
From: Alexandru Matei <alexandru.matei@...ath.com>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: Stefan Hajnoczi <stefanha@...hat.com>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, kvm@...r.kernel.org,
 virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, Mihai Petrisor <mihai.petrisor@...ath.com>,
 Viorel Canja <viorel.canja@...ath.com>,
 Alexandru Matei <alexandru.matei@...ath.com>
Subject: Re: [PATCH v2] vsock/virtio: initialize the_virtio_vsock before using
 VQs

On 10/23/2023 5:29 PM, Stefano Garzarella wrote:
> On Mon, Oct 23, 2023 at 05:08:33PM +0300, Alexandru Matei wrote:
>> Once VQs are filled with empty buffers and we kick the host,
>> it can send connection requests.  If 'the_virtio_vsock' is not
>> initialized before, replies are silently dropped and do not reach the host.
>>
>> Fixes: 0deab087b16a ("vsock/virtio: use RCU to avoid use-after-free on the_virtio_vsock")
>> Signed-off-by: Alexandru Matei <alexandru.matei@...ath.com>
>> ---
>> v2:
>> - split virtio_vsock_vqs_init in vqs_init and vqs_fill and moved
>>  the_virtio_vsock initialization after vqs_init
>>
>> net/vmw_vsock/virtio_transport.c | 9 +++++++--
>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>> index e95df847176b..92738d1697c1 100644
>> --- a/net/vmw_vsock/virtio_transport.c
>> +++ b/net/vmw_vsock/virtio_transport.c
>> @@ -559,6 +559,11 @@ static int virtio_vsock_vqs_init(struct virtio_vsock *vsock)
>>     vsock->tx_run = true;
>>     mutex_unlock(&vsock->tx_lock);
>>
>> +    return 0;
>> +}
>> +
>> +static void virtio_vsock_vqs_fill(struct virtio_vsock *vsock)
> 
> What about renaming this function in virtio_vsock_vqs_start() and move also the setting of `tx_run` here?

It works but in this case we also need to move rcu_assign_pointer in virtio_vsock_vqs_start(), 
the assignment needs to be right after setting tx_run to true and before filling the VQs.

> 
> Thanks,
> Stefano
> 
>> +{
>>     mutex_lock(&vsock->rx_lock);
>>     virtio_vsock_rx_fill(vsock);
>>     vsock->rx_run = true;
>> @@ -568,8 +573,6 @@ static int virtio_vsock_vqs_init(struct virtio_vsock *vsock)
>>     virtio_vsock_event_fill(vsock);
>>     vsock->event_run = true;
>>     mutex_unlock(&vsock->event_lock);
>> -
>> -    return 0;
>> }
>>
>> static void virtio_vsock_vqs_del(struct virtio_vsock *vsock)
>> @@ -664,6 +667,7 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
>>         goto out;
>>
>>     rcu_assign_pointer(the_virtio_vsock, vsock);
>> +    virtio_vsock_vqs_fill(vsock);
>>
>>     mutex_unlock(&the_virtio_vsock_mutex);
>>
>> @@ -736,6 +740,7 @@ static int virtio_vsock_restore(struct virtio_device *vdev)
>>         goto out;
>>
>>     rcu_assign_pointer(the_virtio_vsock, vsock);
>> +    virtio_vsock_vqs_fill(vsock);
>>
>> out:
>>     mutex_unlock(&the_virtio_vsock_mutex);
>> -- 
>> 2.34.1
>>
>