From: Eric Dumazet <edumazet@google.com>
Date: Wed, 19 Apr 2017 16:59:24 +0000 (-0700)
Subject: lan78xx: use skb_cow_head() to deal with cloned skbs
X-Git-Tag: v4.4.112~56
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=efca4f469475f5d0ab0573311b091a2086246834;p=thirdparty%2Fkernel%2Fstable.git

lan78xx: use skb_cow_head() to deal with cloned skbs

commit d4ca73591916b760478d2b04334d5dcadc028e9c upstream.

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: 55d7de9de6c3 ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet device driver")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: James Hughes <james.hughes@raspberrypi.org>
Cc: Woojung Huh <woojung.huh@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 226668ead0d8c..41e9ebd7d0a69 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2050,14 +2050,9 @@ static struct sk_buff *lan78xx_tx_prep(struct lan78xx_net *dev,
 {
 	u32 tx_cmd_a, tx_cmd_b;
 
-	if (skb_headroom(skb) < TX_OVERHEAD) {
-		struct sk_buff *skb2;
-
-		skb2 = skb_copy_expand(skb, TX_OVERHEAD, 0, flags);
+	if (skb_cow_head(skb, TX_OVERHEAD)) {
 		dev_kfree_skb_any(skb);
-		skb = skb2;
-		if (!skb)
-			return NULL;
+		return NULL;
 	}
 
 	if (lan78xx_linearize(skb) < 0)