linux-kernel - Re: [PATCH v2] RDMA/core: Fix race when resolving IP address

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Date:   Fri, 5 Jul 2019 07:09:50 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Parav Pandit <pandit.parav@...il.com>
Cc:     Dag Moxnes <dag.moxnes@...cle.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Parav Pandit <parav@...lanox.com>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] RDMA/core: Fix race when resolving IP address

On Fri, Jul 05, 2019 at 07:49:06AM +0530, Parav Pandit wrote:
> On Fri, Jun 28, 2019 at 2:20 PM Dag Moxnes <dag.moxnes@...cle.com> wrote:
> >
> > Use neighbour lock when copying MAC address from neighbour data struct
> > in dst_fetch_ha.
> >
> > When not using the lock, it is possible for the function to race with
> > neigh_update, causing it to copy an invalid MAC address.
> >
> > It is possible to provoke this error by calling rdma_resolve_addr in a
> > tight loop, while deleting the corresponding ARP entry in another tight
> > loop.
> >
> > Signed-off-by: Dag Moxnes <dag.moxnes@...cle.com>
> > Signed-off-by: Håkon Bugge <haakon.bugge@...cle.com>
> >
> > ---
> > v1 -> v2:
> >    * Modified implementation to improve readability
> > ---
> >  drivers/infiniband/core/addr.c | 9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c
> > index 2f7d141598..51323ffbc5 100644
> > --- a/drivers/infiniband/core/addr.c
> > +++ b/drivers/infiniband/core/addr.c
> > @@ -333,11 +333,14 @@ static int dst_fetch_ha(const struct dst_entry *dst,
> >         if (!n)
> >                 return -ENODATA;
> >
> > -       if (!(n->nud_state & NUD_VALID)) {
> > +       read_lock_bh(&n->lock);
> > +       if (n->nud_state & NUD_VALID) {
> > +               memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN);
> > +               read_unlock_bh(&n->lock);
> > +       } else {
> > +               read_unlock_bh(&n->lock);
> >                 neigh_event_send(n, NULL);
> >                 ret = -ENODATA;
> > -       } else {
> > -               memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN);
> >         }
> >
> >         neigh_release(n);
> > --
> > 2.20.1
> >
> Reviewed-by: Parav Pandit <parav@...lanox.com>
>
> A sample trace such as below in commit message would be good to have.
> Or the similar one that you noticed with ARP delete sequence.
>
> neigh_changeaddr()
>   neigh_flush_dev()
>    n->nud_state = NUD_NOARP;
>
> Having some issues with office outlook, so replying via gmail.

Your replies from gmail looks much better when you used Outlook - proper
spacing between quoted text and your reply.

Thanks