[PATCH 4.14 38/88] net: cdc_eem: fix tx fixup skb leak

From: Sasha Levin
Date: Mon Jun 28 2021 - 11:08:47 EST

From: Linyu Yuan <linyyuan@xxxxxxxxxxxxxx>

[ Upstream commit c3b26fdf1b32f91c7a3bc743384b4a298ab53ad7 ]

when usbnet transmit a skb, eem fixup it in eem_tx_fixup(),
if skb_copy_expand() failed, it return NULL,
usbnet_start_xmit() will have no chance to free original skb.

fix it by free orginal skb in eem_tx_fixup() first,
then check skb clone status, if failed, return NULL to usbnet.

Fixes: 9f722c0978b0 ("usbnet: CDC EEM support (v5)")
Signed-off-by: Linyu Yuan <linyyuan@xxxxxxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/usb/cdc_eem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/usb/cdc_eem.c b/drivers/net/usb/cdc_eem.c
index f7180f8db39e..9c15e1a1261b 100644
--- a/drivers/net/usb/cdc_eem.c
+++ b/drivers/net/usb/cdc_eem.c
@@ -138,10 +138,10 @@ static struct sk_buff *eem_tx_fixup(struct usbnet *dev, struct sk_buff *skb,

skb2 = skb_copy_expand(skb, EEM_HEAD, ETH_FCS_LEN + padlen, flags);
+ dev_kfree_skb_any(skb);
if (!skb2)
return NULL;

- dev_kfree_skb_any(skb);
skb = skb2;