netfilter: nf_tables: initialize registers in nft_do_chain()

Initialize registers to avoid stack leak into userspace.

Fixes: 96518518 ("netfilter: add nftables")
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_core.c

@@ -201,7 +201,7 @@ nft_do_chain(struct nft_pktinfo *pkt, void *priv)
 	const struct nft_rule_dp *rule, *last_rule;
 	const struct net *net = nft_net(pkt);
 	const struct nft_expr *expr, *last;
-	struct nft_regs regs;
+	struct nft_regs regs = {};
 	unsigned int stackptr = 0;
 	struct nft_jumpstack jumpstack[NFT_JUMP_STACK_SIZE];
 	bool genbit = READ_ONCE(net->nft.gencursor);