net: cdc_eem: fix tx fixup skb leak

stable inclusion
from stable-5.10.46
commit 05b2b9f7d24b5663d9b47427fe1555bdafd3ea02
bugzilla: 168323
CVE: NA

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

[ Upstream commit c3b26fdf ]

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: 9f722c09 ("usbnet: CDC EEM support (v5)")
Signed-off-by: Linyu Yuan <linyyuan@codeaurora.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>