nfp: flower: verify that block cb is not busy before binding

When processing FLOW_BLOCK_BIND command on indirect block, check that flow
block cb is not busy.

Fixes: 0d4fd02e ("net: flow_offload: add flow_block_cb_is_busy() and use it")
Reported-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/flower/offload.c

@@ -1416,6 +1416,13 @@ nfp_flower_setup_indr_tc_block(struct net_device *netdev, struct nfp_app *app,
 
 	switch (f->command) {
 	case FLOW_BLOCK_BIND:
+		cb_priv = nfp_flower_indr_block_cb_priv_lookup(app, netdev);
+		if (cb_priv &&
+		    flow_block_cb_is_busy(nfp_flower_setup_indr_block_cb,
+					  cb_priv,
+					  &nfp_block_cb_list))
+			return -EBUSY;
+
 		cb_priv = kmalloc(sizeof(*cb_priv), GFP_KERNEL);
 		if (!cb_priv)
 			return -ENOMEM;