Commit d8d9ec7d authored by Dag Moxnes's avatar Dag Moxnes Committed by Jason Gunthorpe
Browse files

RDMA/core: Fix race when resolving IP address

Use the neighbour lock when copying the MAC address from the 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 torn MAC address:

rdma_resolve_addr()
  rdma_resolve_ip()
    addr_resolve()
      addr_resolve_neigh()
        fetch_ha()
          dst_fetch_ha()
	     memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN)

and

net_ioctl()
  arp_ioctl()
    arp_rec_delete()
      arp_invalidate()
        neigh_update()
          __neigh_update()
	    memcpy(&neigh->ha, lladdr, dev->addr_len)

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.

Fixes: 51d45974

 ("infiniband: addr: Consolidate code to fetch neighbour hardware address from dst.")
Signed-off-by: default avatarDag Moxnes <dag.moxnes@oracle.com>
Signed-off-by: default avatarHåkon Bugge <haakon.bugge@oracle.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@mellanox.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent 390d5772
......@@ -337,7 +337,7 @@ static int dst_fetch_ha(const struct dst_entry *dst,
neigh_event_send(n, NULL);
ret = -ENODATA;
} else {
memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN);
neigh_ha_snapshot(dev_addr->dst_dev_addr, n, dst->dev);
}
neigh_release(n);
......
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