mainline inclusion
from mainline-4.20
commit 876dcf2f3aaa
category: bugfix
bugzilla: 5749
CVE: NA

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

User mode helpers were spawned without a command line, and because
an empty command line is used by many tools to identify processes as
kernel threads, this could cause some issues.

Notably during killing spree on shutdown, since such helper would then
be skipped (i.e. not killed) which would result in the process remaining
alive, and thus preventing unmouting of the rootfs (as experienced with
the bpfilter umh).

Fixes: 449325b5 ("umh: introduce fork_usermode_blob() helper")
Signed-off-by: NOlivier Brunel <jjk@jjacky.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>