Revert "nfp: abm: fix memory leak in nfp_abm_u32_knode_replace"

This reverts commit 78beef62 ("nfp: abm: fix memory leak in
nfp_abm_u32_knode_replace").

The quoted commit does not fix anything and resulted in a bogus
CVE-2019-19076.

If match is NULL then it is known there is no matching entry in
list, hence, calling nfp_abm_u32_knode_delete() is pointless.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: John Hurley <john.hurley@netronome.com>

drivers/net/ethernet/netronome/nfp/abm/cls.c

@@ -176,10 +176,8 @@ nfp_abm_u32_knode_replace(struct nfp_abm_link *alink,
 	u8 mask, val;
 	int err;
 
-	if (!nfp_abm_u32_check_knode(alink->abm, knode, proto, extack)) {
-		err = -EOPNOTSUPP;
+	if (!nfp_abm_u32_check_knode(alink->abm, knode, proto, extack))
 		goto err_delete;
-	}
 
 	tos_off = proto == htons(ETH_P_IP) ? 16 : 20;
 
@@ -200,18 +198,14 @@ nfp_abm_u32_knode_replace(struct nfp_abm_link *alink,
 		if ((iter->val & cmask) == (val & cmask) &&
 		    iter->band != knode->res->classid) {
 			NL_SET_ERR_MSG_MOD(extack, "conflict with already offloaded filter");
-			err = -EOPNOTSUPP;
 			goto err_delete;
 		}
 	}
 
 	if (!match) {
 		match = kzalloc(sizeof(*match), GFP_KERNEL);
-		if (!match) {
-			err = -ENOMEM;
-			goto err_delete;
-		}
-
+		if (!match)
+			return -ENOMEM;
 		list_add(&match->list, &alink->dscp_map);
 	}
 	match->handle = knode->handle;
@@ -227,7 +221,7 @@ nfp_abm_u32_knode_replace(struct nfp_abm_link *alink,
 
 err_delete:
 	nfp_abm_u32_knode_delete(alink, knode);
-	return err;
+	return -EOPNOTSUPP;
 }
 
 static int nfp_abm_setup_tc_block_cb(enum tc_setup_type type,