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

[Jason Gunthorpe]

On Fri, Jul 05, 2019 at 07:09:50AM +0300, Leon Romanovsky wrote:
> 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@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > Signed-off-by: HÃkon Bugge <haakon.bugge@xxxxxxxxxx>
> > >
> > > 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
> > > +++ 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);
> > >
> > Reviewed-by: Parav Pandit <parav@xxxxxxxxxxxx>
> >
> > 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.

Why not use thunderbird or something?

Jason