RDMA/core: Check for verbs callbacks before using them

Make sure the providers implement the verbs callbacks before calling
them, otherwise return -EOPNOTSUPP.
Signed-off-by: Kamal Heib <kamalheib1@gmail.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/uverbs_cmd.c

@@ -2504,7 +2504,8 @@ ssize_t ib_uverbs_post_srq_recv(struct ib_uverbs_file *file,
 		goto out;
 
 	resp.bad_wr = 0;
-	ret = srq->device->post_srq_recv(srq, wr, &bad_wr);
+	ret = srq->device->post_srq_recv ?
+		srq->device->post_srq_recv(srq, wr, &bad_wr) : -EOPNOTSUPP;
 
 	uobj_put_obj_read(srq);
 

drivers/infiniband/core/verbs.c

@@ -479,6 +479,9 @@ static struct ib_ah *_rdma_create_ah(struct ib_pd *pd,
 {
 	struct ib_ah *ah;
 
+	if (!pd->device->create_ah)
+		return ERR_PTR(-EOPNOTSUPP);
+
 	ah = pd->device->create_ah(pd, ah_attr, udata);
 
 	if (!IS_ERR(ah)) {