openvswitch: remove another BUG_ON()

[ Upstream commit 8a574f86652a4540a2433946ba826ccb87f398cc ]

If we can't build the flow del notification, we can simply delete
the flow, no need to crash the kernel. Still keep a WARN_ON to
preserve debuggability.

Note: the BUG_ON() predates the Fixes tag, but this change
can be applied only after the mentioned commit.

v1 -> v2:
 - do not leak an skb on error

Fixes: aed06778 ("openvswitch: Minimize ovs_flow_cmd_del critical section.")
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

net/openvswitch/datapath.c

@@ -1345,7 +1345,10 @@ static int ovs_flow_cmd_del(struct sk_buff *skb, struct genl_info *info)
 						     OVS_FLOW_CMD_DEL,
 						     ufid_flags);
 			rcu_read_unlock();
-			BUG_ON(err < 0);
+			if (WARN_ON_ONCE(err < 0)) {
+				kfree_skb(reply);
+				goto out_free;
+			}
 
 			ovs_notify(&dp_flow_genl_family, reply, info);
 		} else {
@@ -1353,6 +1356,7 @@ static int ovs_flow_cmd_del(struct sk_buff *skb, struct genl_info *info)
 		}
 	}
 
+out_free:
 	ovs_flow_free(flow, true);
 	return 0;
 unlock: