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Subject[PATCH 4.4 40/87] smsc75xx: use skb_cow_head() to deal with cloned skbs
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Eric Dumazet <edumazet@google.com>

commit b7c6d2675899cfff0180412c63fc9cbd5bacdb4d 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: d0cad871703b ("smsc75xx: SMSC LAN75xx USB gigabit ethernet adapter driver")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: James Hughes <james.hughes@raspberrypi.org>
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>

---
drivers/net/usb/smsc75xx.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

--- a/drivers/net/usb/smsc75xx.c
+++ b/drivers/net/usb/smsc75xx.c
@@ -2193,13 +2193,9 @@ static struct sk_buff *smsc75xx_tx_fixup
{
u32 tx_cmd_a, tx_cmd_b;

- if (skb_headroom(skb) < SMSC75XX_TX_OVERHEAD) {
- struct sk_buff *skb2 =
- skb_copy_expand(skb, SMSC75XX_TX_OVERHEAD, 0, flags);
+ if (skb_cow_head(skb, SMSC75XX_TX_OVERHEAD)) {
dev_kfree_skb_any(skb);
- skb = skb2;
- if (!skb)
- return NULL;
+ return NULL;
}

tx_cmd_a = (u32)(skb->len & TX_CMD_A_LEN) | TX_CMD_A_FCS;

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