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Subject: Re: [PATCH net V2] vhost-vsock: fix use after free
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     stefanha@redhat.com, kvm@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, sergei.shtylyov@cogentembedded.com
References: <20180927122204.4188-1-jasowang@redhat.com>
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From:   Jason Wang <jasowang@redhat.com>
Message-ID: <588ed28b-7e4b-9dc8-92ce-d75692836c9e@redhat.com>
Date:   Fri, 28 Sep 2018 07:37:37 +0800
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On 2018年09月28日 01:04, Michael S. Tsirkin wrote:
> On Thu, Sep 27, 2018 at 08:22:04PM +0800, Jason Wang wrote:
>> The access of vsock is not protected by vhost_vsock_lock. This may
>> lead to use after free since vhost_vsock_dev_release() may free the
>> pointer at the same time.
>>
>> Fix this by holding the lock during the access.
>>
>> Reported-by:syzbot+e3e074963495f92a89ed@syzkaller.appspotmail.com
>> Fixes: 16320f363ae1 ("vhost-vsock: add pkt cancel capability")
>> Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
>> Cc: Stefan Hajnoczi<stefanha@redhat.com>
>> Signed-off-by: Jason Wang<jasowang@redhat.com>
> Wow is that really the best we can do?

For net/stable, probably yes.

>   A global lock on a data path
> operation?

It's already there, and the patch only increase the critical section.

>   Granted use after free is nasty but Stefan said he sees
> a way to fix it using a per socket refcount. He's on vacation
> until Oct 4 though ...
>

Stefan has acked the pacth, so I think it's ok? We can do optimization 
for -next on top.

Thanks