net/netlink: fix NETLINK_LIST_MEMBERSHIPS length report

stable inclusion
from stable-v4.19.285
commit 16072e1e6ec237c9d8decdce0758f7629c175354
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7J5UF
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=16072e1e6ec237c9d8decdce0758f7629c175354



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[ Upstream commit f4e45348 ]

The current code for the length calculation wrongly truncates the reported
length of the groups array, causing an under report of the subscribed
groups. To fix this, use 'BITS_TO_BYTES()' which rounds up the
division by 8.

Fixes: b42be38b ("netlink: add API to retrieve all group memberships")
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230529153335.389815-1-pctammela@mojatatu.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Conflicts:
	net/netlink/af_netlink.c
	include/linux/bitops.h
Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com>
Reviewed-by: Yue Haibing <yuehaibing@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>