netdev - [PATCH net 2/6] cx82310_eth: use skb_cow

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Message-Id: <20170419165926.30631-3-edumazet@google.com>
Date:   Wed, 19 Apr 2017 09:59:22 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        James Hughes <james.hughes@...pberrypi.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net 2/6] cx82310_eth: use skb_cow_head() to deal with cloned skbs

We need to ensure there is enough headroom to push extra header,
but we also need to check if we are allowed to change headers.

skb_cow_head() is the proper helper to deal with this.

Fixes: cc28a20e77b2 ("introduce cx82310_eth: Conexant CX82310-based ADSL router USB ethernet driver")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: James Hughes <james.hughes@...pberrypi.org>
---
 drivers/net/usb/cx82310_eth.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/net/usb/cx82310_eth.c b/drivers/net/usb/cx82310_eth.c
index e221bfcee76b40a3ad7ba60ec4d348f4b8f4cc73..947bea81d924124c3827e87f75e732e35adb2acd 100644
--- a/drivers/net/usb/cx82310_eth.c
+++ b/drivers/net/usb/cx82310_eth.c
@@ -293,12 +293,9 @@ static struct sk_buff *cx82310_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
 {
 	int len = skb->len;
 
-	if (skb_headroom(skb) < 2) {
-		struct sk_buff *skb2 = skb_copy_expand(skb, 2, 0, flags);
+	if (skb_cow_head(skb, 2)) {
 		dev_kfree_skb_any(skb);
-		skb = skb2;
-		if (!skb)
-			return NULL;
+		return NULL;
 	}
 	skb_push(skb, 2);
 
-- 
2.12.2.816.g2cccc81164-goog