target/linux/generic/patches-4.4/030-1-smsc95xx-Use-skb_cow_head-to-deal-with-cloned-skbs.patch

   1 From e9156cd26a495a18706e796f02a81fee41ec14f4 Mon Sep 17 00:00:00 2001
   2 From: James Hughes <james.hughes@raspberrypi.org>
   3 Date: Wed, 19 Apr 2017 11:13:40 +0100
   4 Subject: [PATCH] smsc95xx: Use skb_cow_head to deal with cloned skbs
   5
   6 The driver was failing to check that the SKB wasn't cloned
   7 before adding checksum data.
   8 Replace existing handling to extend/copy the header buffer
   9 with skb_cow_head.
  10
  11 Signed-off-by: James Hughes <james.hughes@raspberrypi.org>
  12 Acked-by: Eric Dumazet <edumazet@google.com>
  13 Acked-by: Woojung Huh <Woojung.Huh@microchip.com>
  14 Signed-off-by: David S. Miller <davem@davemloft.net>
  15 ---
  16  drivers/net/usb/smsc95xx.c | 12 ++++++------
  17  1 file changed, 6 insertions(+), 6 deletions(-)
  18
  19 --- a/drivers/net/usb/smsc95xx.c
  20 +++ b/drivers/net/usb/smsc95xx.c
  21 @@ -1835,13 +1835,13 @@ static struct sk_buff *smsc95xx_tx_fixup
  22         /* We do not advertise SG, so skbs should be already linearized */
  23         BUG_ON(skb_shinfo(skb)->nr_frags);
  24
  25 -       if (skb_headroom(skb) < overhead) {
  26 -               struct sk_buff *skb2 = skb_copy_expand(skb,
  27 -                       overhead, 0, flags);
  28 +       /* Make writable and expand header space by overhead if required */
  29 +       if (skb_cow_head(skb, overhead)) {
  30 +               /* Must deallocate here as returning NULL to indicate error
  31 +                * means the skb won't be deallocated in the caller.
  32 +                */
  33                 dev_kfree_skb_any(skb);
  34 -               skb = skb2;
  35 -               if (!skb)
  36 -                       return NULL;
  37 +               return NULL;
  38         }
  39
  40         if (csum) {