linux-kernel - RE: [PATCH net-next 2/3] vsock: fix vsock_dequeue/enqueue

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Message-ID: <KL1P15301MB0008245B174ABA9C85A49382BF800@KL1P15301MB0008.APCP153.PROD.OUTLOOK.COM>
Date:   Fri, 18 Aug 2017 21:13:05 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Stefan Hajnoczi <stefanha@...hat.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        KY Srinivasan <kys@...rosoft.com>,
        "Haiyang Zhang" <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        George Zhang <georgezhang@...are.com>,
        Jorgen Hansen <jhansen@...are.com>,
        Michal Kubecek <mkubecek@...e.cz>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Cathy Avery <cavery@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        Rolf Neugebauer <rolf.neugebauer@...ker.com>,
        Dave Scott <dave.scott@...ker.com>,
        Marcelo Cerri <marcelo.cerri@...onical.com>,
        "apw@...onical.com" <apw@...onical.com>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "joe@...ches.com" <joe@...ches.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: RE: [PATCH net-next 2/3] vsock: fix vsock_dequeue/enqueue_accept race

> From: Stefan Hajnoczi [mailto:stefanha@...hat.com]
> Sent: Thursday, August 17, 2017 07:06
> 
> On Tue, Aug 15, 2017 at 10:15:39PM +0000, Dexuan Cui wrote:
> > With the current code, when vsock_dequeue_accept() is removing a sock
> > from the list, nothing prevents vsock_enqueue_accept() from adding a new
> > sock into the list concurrently. We should add a lock to protect the list.
> 
> The listener sock is locked, preventing concurrent modification.  I have
> checked both the virtio and vmci transports.  Can you post an example
> where the listener sock isn't locked?
> 
> Stefan
Sorry, I was not careful when checking the vmci code. 
Please ignore the patch.

Now I realized the expectation is that the individual transport drivers should
do the locking for vsock_enqueue_accept(), but for vsock_dequeue_accept(),
the locking is done by the common vsock driver.

Thanks,
-- Dexuan