kobject_uevent: remove warning in init_uevent_argv()

stable inclusion
from linux-4.19.191
commit 1ea5cdd5388628a6e3762392717db0d980307ce8

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

commit b4104180 upstream.

syzbot can trigger the WARN() in init_uevent_argv() which isn't the
nicest as the code does properly recover and handle the error.  So
change the WARN() call to pr_warn() and provide some more information on
what the buffer size that was needed.

Link: https://lore.kernel.org/r/20201107082206.GA19079@kroah.com


Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: linux-kernel@vger.kernel.org
Reported-by:  <syzbot+92340f7b2b4789907fdb@syzkaller.appspotmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20210405094852.1348499-1-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>