[OpenWrt-Devel] [PATCH 2/8 v3] smsc95xx: Use skb_cow_head to deal with cloned skbs

[Linus Walleij]

From: James Hughes <james.hughes at raspberrypi.org>

commit e9156cd26a495a18706e796f02a81fee41ec14f4 upstream.

The driver was failing to check that the SKB wasn't cloned
before adding checksum data.
Replace existing handling to extend/copy the header buffer
with skb_cow_head.

Signed-off-by: James Hughes <james.hughes at raspberrypi.org>
Acked-by: Eric Dumazet <edumazet at google.com>
Acked-by: Woojung Huh <Woojung.Huh at microchip.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
- This was applied upstream in v4.11
- Should be applied to stable v4.9.y
---
 drivers/net/usb/smsc95xx.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index e29f4c0767eb..e719ecd69d01 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -2011,13 +2011,13 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
 	/* We do not advertise SG, so skbs should be already linearized */
 	BUG_ON(skb_shinfo(skb)->nr_frags);
 
-	if (skb_headroom(skb) < overhead) {
-		struct sk_buff *skb2 = skb_copy_expand(skb,
-			overhead, 0, flags);
+	/* Make writable and expand header space by overhead if required */
+	if (skb_cow_head(skb, overhead)) {
+		/* Must deallocate here as returning NULL to indicate error
+		 * means the skb won't be deallocated in the caller.
+		 */
 		dev_kfree_skb_any(skb);
-		skb = skb2;
-		if (!skb)
-			return NULL;
+		return NULL;
 	}
 
 	if (csum) {
-- 
2.20.1


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