RDMA/mlx5: Block delay drop to unprivileged users

It has been discovered that this feature can globally block the RX port,
so it should be allowed for highly privileged users only.

Fixes: 03404e8("IB/mlx5: Add support to dropless RQ")
Link: https://lore.kernel.org/r/20200322124906.1173790-1-leon@kernel.org
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx5/qp.c

@@ -6205,6 +6205,10 @@ struct ib_wq *mlx5_ib_create_wq(struct ib_pd *pd,
 	if (udata->outlen && udata->outlen < min_resp_len)
 		return ERR_PTR(-EINVAL);
 
+	if (!capable(CAP_SYS_RAWIO) &&
+	    init_attr->create_flags & IB_WQ_FLAGS_DELAY_DROP)
+		return ERR_PTR(-EPERM);
+
 	dev = to_mdev(pd->device);
 	switch (init_attr->wq_type) {
 	case IB_WQT_RQ: