linux-kernel - Re: [PATCH RFC 1/4] vsock/virtio: reduce credit update messages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 8 Apr 2019 10:25:39 +0100
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     Stefan Hajnoczi <stefanha@...il.com>, netdev@...r.kernel.org,
        Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH RFC 1/4] vsock/virtio: reduce credit update messages

On Fri, Apr 05, 2019 at 10:16:48AM +0200, Stefano Garzarella wrote:
> On Thu, Apr 04, 2019 at 08:15:39PM +0100, Stefan Hajnoczi wrote:
> > On Thu, Apr 04, 2019 at 12:58:35PM +0200, Stefano Garzarella wrote:
> > >  	int err = -EFAULT;
> > >  
> > >  	spin_lock_bh(&vvs->rx_lock);
> > > @@ -288,9 +290,15 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> > >  	}
> > >  	spin_unlock_bh(&vvs->rx_lock);
> > >  
> > > -	/* Send a credit pkt to peer */
> > > -	virtio_transport_send_credit_update(vsk, VIRTIO_VSOCK_TYPE_STREAM,
> > > -					    NULL);
> > > +	/* We send a credit update only when the space available seen
> > > +	 * by the transmitter is less than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE
> > > +	 */
> > > +	free_space = vvs->buf_alloc - (vvs->fwd_cnt - vvs->last_fwd_cnt);
> > 
> > Locking?  These fields should be accessed under tx_lock.
> > 
> 
> Yes, we need a lock, but looking in the code, vvs->fwd_cnd is written
> taking rx_lock (virtio_transport_dec_rx_pkt) and it is read with the
> tx_lock (virtio_transport_inc_tx_pkt).
> 
> Maybe we should use another spin_lock shared between RX and TX for those
> fields or use atomic variables.
> 
> What do you suggest?

Or make vvs->fwd_cnt atomic if it's the only field that needs to be
accessed in this manner.

Stefan

Download attachment "signature.asc" of type "application/pgp-signature" (456 bytes)