netfilter: nf_tables: initialize registers in nft_do_chain()

ANBZ: torvalds#740

commit 4c905f6 upstream.

Initialize registers to avoid stack leak into userspace.

Fixes: 9651851 ("netfilter: add nftables")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Fixes: CVE-2022-1016
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Dust Li <dust.li@linux.alibaba.com>

net/netfilter/nf_tables_core.c

@@ -144,7 +144,7 @@ nft_do_chain(struct nft_pktinfo *pkt, void *priv)
 	struct nft_rule *const *rules;
 	const struct nft_rule *rule;
 	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);