usbnet: fix memory leak in error case

stable inclusion
from stable-4.19.252
commit d5165e657987ff4ba0ace896d4376a3718a9fbc3
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5I4FP


CVE: NA

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

commit b55a21b7 upstream.

usbnet_write_cmd_async() mixed up which buffers
need to be freed in which error case.

v2: add Fixes tag
v3: fix uninitialized buf pointer

Fixes: 877bd862 ("usbnet: introduce usbnet 3 command helpers")
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20220705125351.17309-1-oneukum@suse.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>