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

[Dag Moxnes]

Den 05.07.2019 04:19, skrev Parav Pandit:
> 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
> > --- 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@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.

Hi Parav,

Thanks for your review. I'll add a sample trace to the commit message as

you suggest.


Regards,

-Dag