nfp: flower: check that we don't exceed the FW key size

Add a check to make sure the total length of the flow key sent to the
firmware stays within the supported limit.

Signed-off-by: Louis Peens <louis.peens@netronome.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/flower/main.h

@@ -30,6 +30,8 @@ struct nfp_app;
 #define NFP_FLOWER_MASK_ELEMENT_RS	1
 #define NFP_FLOWER_MASK_HASH_BITS	10
 
+#define NFP_FLOWER_KEY_MAX_LW		32
+
 #define NFP_FL_META_FLAG_MANAGE_MASK	BIT(7)
 
 #define NFP_FL_MASK_REUSE_TIME_NS	40000

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

@@ -434,6 +434,7 @@ int nfp_flower_compile_flow_match(struct nfp_app *app,
 {
 	struct flow_rule *rule = flow_cls_offload_flow_rule(flow);
 	u32 port_id;
+	int ext_len;
 	int err;
 	u8 *ext;
 	u8 *msk;
@@ -589,5 +590,15 @@ int nfp_flower_compile_flow_match(struct nfp_app *app,
 		}
 	}
 
+	/* Check that the flow key does not exceed the maximum limit.
+	 * All structures in the key is multiples of 4 bytes, so use u32.
+	 */
+	ext_len = (u32 *)ext - (u32 *)nfp_flow->unmasked_data;
+	if (ext_len > NFP_FLOWER_KEY_MAX_LW) {
+		NL_SET_ERR_MSG_MOD(extack,
+				   "unsupported offload: flow key too long");
+		return -EOPNOTSUPP;
+	}
+
 	return 0;
 }