From: Julian Wiedmann <jwi@linux.ibm.com>
Date: Thu, 14 Nov 2019 11:19:16 +0100
Subject: s390/qeth: drop unwanted packets earlier in RX path
Git-commit: 7d4faee7c6db9ddfb2b4de637dc6f1576f780bd7
Patch-mainline: v5.5-rc1
References: jsc#SLE-7474

Packets with an unexpected HW format are currently first extracted from
the RX buffer, passed upwards to the layer-specific driver and only then
finally dropped.

Enhance the RX path so that we can drop such packets before even
allocating an skb. For this, add some additional logic so that when a
packet is meant to be dropped, we can still walk along the packet's data
chunks in the RX buffer. This allows us to extract the following
packet(s) from the buffer.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/s390/net/qeth_core_main.c |   32 ++++++++++++++++++++++++++++----
 drivers/s390/net/qeth_l2_main.c   |   27 ++++++++-------------------
 drivers/s390/net/qeth_l3_main.c   |   26 ++++++++------------------
 3 files changed, 44 insertions(+), 41 deletions(-)

--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -5072,6 +5072,7 @@ struct sk_buff *qeth_core_get_next_skb(s
 	int headroom = 0;
 	int use_rx_sg = 0;
 
+next_packet:
 	/* qeth_hdr must not cross element boundaries */
 	while (element->length < offset + sizeof(struct qeth_hdr)) {
 		if (qeth_is_last_sbale(element))
@@ -5088,10 +5089,22 @@ struct sk_buff *qeth_core_get_next_skb(s
 		break;
 	case QETH_HEADER_TYPE_LAYER3:
 		skb_len = (*hdr)->hdr.l3.length;
+		if (!IS_LAYER3(card)) {
+			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
+			skb = NULL;
+			goto walk_packet;
+		}
+
 		headroom = ETH_HLEN;
 		break;
 	case QETH_HEADER_TYPE_OSN:
 		skb_len = (*hdr)->hdr.osn.pdu_length;
+		if (!IS_OSN(card)) {
+			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
+			skb = NULL;
+			goto walk_packet;
+		}
+
 		headroom = sizeof(struct qeth_hdr);
 		break;
 	default:
@@ -5100,7 +5113,8 @@ struct sk_buff *qeth_core_get_next_skb(s
 		else
 			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
 
-		break;
+		/* Can't determine packet length, drop the whole buffer. */
+		return NULL;
 	}
 
 	if (!skb_len)
@@ -5126,10 +5140,12 @@ struct sk_buff *qeth_core_get_next_skb(s
 	if (headroom)
 		skb_reserve(skb, headroom);
 
+walk_packet:
 	data_ptr = element->addr + offset;
 	while (skb_len) {
 		data_len = min(skb_len, (int)(element->length - offset));
-		if (data_len) {
+
+		if (skb && data_len) {
 			if (use_rx_sg)
 				qeth_create_skb_frag(element, skb, offset,
 						     data_len);
@@ -5141,8 +5157,11 @@ struct sk_buff *qeth_core_get_next_skb(s
 			if (qeth_is_last_sbale(element)) {
 				QETH_CARD_TEXT(card, 4, "unexeob");
 				QETH_CARD_HEX(card, 2, buffer, sizeof(void *));
-				dev_kfree_skb_any(skb);
-				QETH_CARD_STAT_INC(card, rx_length_errors);
+				if (skb) {
+					dev_kfree_skb_any(skb);
+					QETH_CARD_STAT_INC(card,
+							   rx_length_errors);
+				}
 				return NULL;
 			}
 			element++;
@@ -5152,6 +5171,11 @@ struct sk_buff *qeth_core_get_next_skb(s
 			offset += data_len;
 		}
 	}
+
+	/* This packet was skipped, go get another one: */
+	if (!skb)
+		goto next_packet;
+
 	*__element = element;
 	*__offset = offset;
 	if (use_rx_sg) {
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -315,30 +315,19 @@ static int qeth_l2_process_inbound_buffe
 			*done = 1;
 			break;
 		}
-		switch (hdr->hdr.l2.id) {
-		case QETH_HEADER_TYPE_LAYER2:
+
+		if (hdr->hdr.l2.id == QETH_HEADER_TYPE_LAYER2) {
 			skb->protocol = eth_type_trans(skb, skb->dev);
 			qeth_rx_csum(card, skb, hdr->hdr.l2.flags[1]);
 			len = skb->len;
 			napi_gro_receive(&card->napi, skb);
-			break;
-		case QETH_HEADER_TYPE_OSN:
-			if (IS_OSN(card)) {
-				skb_push(skb, sizeof(struct qeth_hdr));
-				skb_copy_to_linear_data(skb, hdr,
-						sizeof(struct qeth_hdr));
-				len = skb->len;
-				card->osn_info.data_cb(skb);
-				break;
-			}
-			/* Else, fall through */
-		default:
-			dev_kfree_skb_any(skb);
-			QETH_CARD_TEXT(card, 3, "inbunkno");
-			QETH_DBF_HEX(CTRL, 3, hdr, sizeof(*hdr));
-			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
-			continue;
+		} else {
+			skb_push(skb, sizeof(*hdr));
+			skb_copy_to_linear_data(skb, hdr, sizeof(*hdr));
+			len = skb->len;
+			card->osn_info.data_cb(skb);
 		}
+
 		work_done++;
 		budget--;
 		QETH_CARD_STAT_INC(card, rx_packets);
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -1366,7 +1366,6 @@ static int qeth_l3_process_inbound_buffe
 	int work_done = 0;
 	struct sk_buff *skb;
 	struct qeth_hdr *hdr;
-	unsigned int len;
 
 	*done = 0;
 	WARN_ON_ONCE(!budget);
@@ -1378,26 +1377,17 @@ static int qeth_l3_process_inbound_buffe
 			*done = 1;
 			break;
 		}
-		switch (hdr->hdr.l3.id) {
-		case QETH_HEADER_TYPE_LAYER3:
+
+		if (hdr->hdr.l3.id == QETH_HEADER_TYPE_LAYER3)
 			qeth_l3_rebuild_skb(card, skb, hdr);
-			/* fall through */
-		case QETH_HEADER_TYPE_LAYER2: /* for HiperSockets sniffer */
-			skb->protocol = eth_type_trans(skb, skb->dev);
-			len = skb->len;
-			napi_gro_receive(&card->napi, skb);
-			break;
-		default:
-			dev_kfree_skb_any(skb);
-			QETH_CARD_TEXT(card, 3, "inbunkno");
-			QETH_DBF_HEX(CTRL, 3, hdr, sizeof(*hdr));
-			QETH_CARD_STAT_INC(card, rx_dropped_notsupp);
-			continue;
-		}
+
+		skb->protocol = eth_type_trans(skb, skb->dev);
+		QETH_CARD_STAT_INC(card, rx_packets);
+		QETH_CARD_STAT_ADD(card, rx_bytes, skb->len);
+
+		napi_gro_receive(&card->napi, skb);
 		work_done++;
 		budget--;
-		QETH_CARD_STAT_INC(card, rx_packets);
-		QETH_CARD_STAT_ADD(card, rx_bytes, len);
 	}
 	return work_done;
 }