linux-kernel - [PATCH 4.19 41/43] netfilter: conntrack: fix reading nf_conntrack

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Message-Id: <20210118113336.921993504@linuxfoundation.org>
Date:   Mon, 18 Jan 2021 12:35:04 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yoel Caspersen <yoel@...knet.dk>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Florian Westphal <fw@...len.de>,
        Pablo Neira Ayuso <pablo@...filter.org>
Subject: [PATCH 4.19 41/43] netfilter: conntrack: fix reading nf_conntrack_buckets

From: Jesper Dangaard Brouer <brouer@...hat.com>

commit f6351c3f1c27c80535d76cac2299aec44c36291e 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 3183ab8997a4 ("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: 3183ab8997a4 ("netfilter: conntrack: allow increasing bucket size via sysctl too")
Reported-by: Yoel Caspersen <yoel@...knet.dk>
Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
Acked-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/netfilter/nf_conntrack_standalone.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -500,6 +500,9 @@ nf_conntrack_hash_sysctl(struct ctl_tabl
 {
 	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;