netfilter: nft_exthdr: break evaluation if setting TCP option fails

Break rule evaluation on malformed TCP options.

Fixes: 99d1712bc41c ("netfilter: exthdr: tcp option set support")
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/netfilter/nft_exthdr.c

···
 
 	tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
 	if (!tcph)
-		return;
+		goto err;
 
 	opt = (u8 *)tcph;
 	for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
···
 			continue;
 
 		if (i + optl > tcphdr_len || priv->len + priv->offset > optl)
-			return;
+			goto err;
 
 		if (skb_ensure_writable(pkt->skb,
 					nft_thoff(pkt) + i + priv->len))
-			return;
+			goto err;
 
 		tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff,
 					      &tcphdr_len);
 		if (!tcph)
-			return;
+			goto err;
 
 		offset = i + priv->offset;
 
···
 
 		return;
 	}
+	return;
+err:
+	regs->verdict.code = NFT_BREAK;
 }
 
 static void nft_exthdr_sctp_eval(const struct nft_expr *expr,