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

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Message-ID: <E062F976-DF33-46CB-AB17-07F014AE138A@vmware.com>
Date:   Thu, 17 Aug 2017 12:43:23 +0000
From:   "Jorgen S. Hansen" <jhansen@...are.com>
To:     Dexuan Cui <decui@...rosoft.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.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>,
        Michal Kubecek <mkubecek@...e.cz>, Asias He <asias@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "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


> On Aug 16, 2017, at 12:15 AM, Dexuan Cui <decui@...rosoft.com> 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.
> 

For the VMCI socket transport, we always lock the sockets before calling into vsock_enqueue_accept and af_vsock.c locks the socket before calling vsock_dequeue_accept, so from our point of view these operations are already protected, but with finer granularity than a single global lock. As far as I can see, the virtio transport also locks the socket before calling vsock_enqueue_accept, so they should be fine with the current version as well, but Stefan can comment on that.

Thanks,
Jorgen