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

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

[ 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: NPedro Tammela <pctammela@mojatatu.com>
Reviewed-by: NSimon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230529153335.389815-1-pctammela@mojatatu.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Conflicts:
	net/netlink/af_netlink.c
	include/linux/bitops.h
Signed-off-by: NDong Chenchen <dongchenchen2@huawei.com>
Reviewed-by: NYue Haibing <yuehaibing@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

include/linux/bitops.h

@@ -6,6 +6,7 @@
 
 #define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE)
 #define BITS_TO_LONGS(nr)	DIV_ROUND_UP(nr, BITS_PER_TYPE(long))
+#define BITS_TO_BYTES(nr)       DIV_ROUND_UP(nr, BITS_PER_TYPE(char))
 
 extern unsigned int __sw_hweight8(unsigned int w);
 extern unsigned int __sw_hweight16(unsigned int w);

net/netlink/af_netlink.c

@@ -1795,7 +1795,7 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
 				break;
 			}
 		}
-		if (put_user(ALIGN(nlk->ngroups / 8, sizeof(u32)), optlen))
+		if (put_user(ALIGN(BITS_TO_BYTES(nlk->ngroups), sizeof(u32)), optlen))
 			err = -EFAULT;
 		netlink_unlock_table();
 		break;