netfilter: nf_tables: fix update chain error

 # nft add table filter
 # nft add chain filter c1
 # nft rename chain filter c1 c2

Error: Could not process rule: No such file or directory rename chain filter c1 c2 ^^^^^^^^^^^^^^^^^^^^^^^^^^

 # nft add chain filter c2
 # nft rename chain filter c1 c2
 # nft list table filter

table ip filter {
	chain c2 {
	}

	chain c2 {
	}
}

---
 net/netfilter/nf_tables_api.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 9299271..f98ca8c 100644
@@ -1487,8 +1487,8 @@ static int nf_tables_updchain(struct nft_ctx *ctx, u8 genmask, u8 policy,
 
 		chain2 = nf_tables_chain_lookup(table, nla[NFTA_CHAIN_NAME],
 						genmask);
-		if (IS_ERR(chain2))
-			return PTR_ERR(chain2);
+		if (!IS_ERR(chain2))
+			return -EEXIST;
 	}
 
 	if (nla[NFTA_CHAIN_COUNTERS]) {

2.7.4

Applied, thanks.