netdev - Re: [PATCH] vsock/virtio: fix kernel panic from virtio_transport_reset_no

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Message-ID: <20190306170216.GC29057@stefanha-x1.localdomain>
Date:   Wed, 6 Mar 2019 17:02:16 +0000
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     Adalbert Lazăr <alazar@...defender.com>
Cc:     Stefan Hajnoczi <stefanha@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Stefano Garzarella <sgarzare@...hat.com>,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vsock/virtio: fix kernel panic from
 virtio_transport_reset_no_sock

On Wed, Mar 06, 2019 at 11:10:41AM +0200, Adalbert Lazăr wrote:
> On Wed, 6 Mar 2019 08:41:04 +0000, Stefan Hajnoczi <stefanha@...il.com> wrote:
> > On Tue, Mar 05, 2019 at 08:01:45PM +0200, Adalbert Lazăr wrote:
> > The pkt argument is the received packet that we must reply to.
> > The reply packet is allocated just before line 680 and must be free
> > explicitly for return -ENOTCONN.
> > 
> > You can avoid the leak and make the code easier to read like this:
> > 
> >   struct virtio_vsock_pkt *reply;
> > 
> >   ...
> > 
> >      ------ avoid reusing 'pkt'
> >     v
> >   reply = virtio_transport_alloc_pkt(&info, 0, ...);
> >   if (!reply)
> >       return -ENOMEM;
> > 
> >   t = virtio_transport_get_ops();
> >   if (!t) {
> >       virtio_transport_free_pkt(reply); <-- prevent memory leak
> >       return -ENOTCONN;
> >   }
> >   return t->send_pkt(reply);
> 
> What do you think about Stefano's suggestion, to move the check above
> the line were the reply is allocated?

That's fine too.

However a follow up patch to eliminate the confusing way that 'pkt' is
reused is still warranted.  If you are busy I'd be happy to send that
cleanup.

Stefan

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