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SubjectRe: [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@oracle.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@oracle.com>
> > Signed-off-by: Håkon Bugge <haakon.bugge@oracle.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@mellanox.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

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