[PATCH 3.18 105/108] smsc95xx: Use skb_cow_head to deal with cloned skbs

From: Greg Kroah-Hartman
Date: Mon Feb 18 2019 - 09:14:12 EST


3.18-stable review patch. If anyone has any objections, please let me know.

------------------

From: James Hughes <james.hughes@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Acked-by: Woojung Huh <Woojung.Huh@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/net/usb/smsc95xx.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1841,13 +1841,13 @@ static struct sk_buff *smsc95xx_tx_fixup
/* 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) {