netdev - [PATCH net-next 11/13] s390/qeth: try harder to get packets from RX buffer

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Message-Id: <20171018154025.73630-12-jwi@linux.vnet.ibm.com>
Date:   Wed, 18 Oct 2017 17:40:23 +0200
From:   Julian Wiedmann <jwi@...ux.vnet.ibm.com>
To:     David Miller <davem@...emloft.net>
Cc:     <netdev@...r.kernel.org>, <linux-s390@...r.kernel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Stefan Raspl <raspl@...ux.vnet.ibm.com>,
        Ursula Braun <ubraun@...ux.vnet.ibm.com>,
        Julian Wiedmann <jwi@...ux.vnet.ibm.com>
Subject: [PATCH net-next 11/13] s390/qeth: try harder to get packets from RX buffer

Current code bails out when two subsequent buffer elements hold
insufficient data to contain a qeth_hdr packet descriptor.
This seems reasonable, but it would be legal for quirky hardware to
leave a few elements empty and then present packets in a subsequent
element. These packets would currently be dropped.

So make sure to check all buffer elements, until we hit the LAST_ENTRY
indication.

Signed-off-by: Julian Wiedmann <jwi@...ux.vnet.ibm.com>
---
 drivers/s390/net/qeth_core_main.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 23b439fb5f2c..8855bc8534d2 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -5214,13 +5214,11 @@ struct sk_buff *qeth_core_get_next_skb(struct qeth_card *card,
 	int use_rx_sg = 0;
 
 	/* qeth_hdr must not cross element boundaries */
-	if (element->length < offset + sizeof(struct qeth_hdr)) {
+	while (element->length < offset + sizeof(struct qeth_hdr)) {
 		if (qeth_is_last_sbale(element))
 			return NULL;
 		element++;
 		offset = 0;
-		if (element->length < sizeof(struct qeth_hdr))
-			return NULL;
 	}
 	*hdr = element->addr + offset;
 
-- 
2.13.5