net/netlink: fix NETLINK_LIST_MEMBERSHIPS length report

[ Upstream commit f4e4534850a9d18c250a93f8d7fbb51310828110 ]

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: b42be38b2778 ("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>

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index d1b1961..6d493a0 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1768,7 +1768,7 @@ 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();
                return err;