netfilter: nf_tables: use WARN_ON_ONCE instead of BUG_ON in nft_do_chain()

When depth of chain is bigger than NFT_JUMP_STACK_SIZE, the nft_do_chain
crashes. But there is no need to crash hard here.
Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_core.c

@@ -183,7 +183,8 @@ nft_do_chain(struct nft_pktinfo *pkt, void *priv)
 
 	switch (regs.verdict.code) {
 	case NFT_JUMP:
-		BUG_ON(stackptr >= NFT_JUMP_STACK_SIZE);
+		if (WARN_ON_ONCE(stackptr >= NFT_JUMP_STACK_SIZE))
+			return NF_DROP;
 		jumpstack[stackptr].chain = chain;
 		jumpstack[stackptr].rules = rules + 1;
 		stackptr++;