netfilter: conntrack: fix reading nf_conntrack_buckets

stable inclusion
from stable-5.10.9
commit f14e31c169dc689f47929bc3729ac019eea02d89
bugzilla: 47457

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

commit f6351c3f upstream.

The old way of changing the conntrack hashsize runtime was through changing
the module param via file /sys/module/nf_conntrack/parameters/hashsize. This
was extended to sysctl change in commit 3183ab89 ("netfilter: conntrack:
allow increasing bucket size via sysctl too").

The commit introduced second "user" variable nf_conntrack_htable_size_user
which shadow actual variable nf_conntrack_htable_size. When hashsize is
changed via module param this "user" variable isn't updated. This results in
sysctl net/netfilter/nf_conntrack_buckets shows the wrong value when users
update via the old way.

This patch fix the issue by always updating "user" variable when reading the
proc file. This will take care of changes to the actual variable without
sysctl need to be aware.

Fixes: 3183ab89 ("netfilter: conntrack: allow increasing bucket size via sysctl too")
Reported-by: NYoel Caspersen <yoel@kviknet.dk>
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Acked-by: NFlorian Westphal <fw@strlen.de>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

net/netfilter/nf_conntrack_standalone.c

@@ -523,6 +523,9 @@ nf_conntrack_hash_sysctl(struct ctl_table *table, int write,
 {
 	int ret;
 
+	/* module_param hashsize could have changed value */
+	nf_conntrack_htable_size_user = nf_conntrack_htable_size;
+
 	ret = proc_dointvec(table, write, buffer, lenp, ppos);
 	if (ret < 0 || !write)
 		return ret;