netdev - [PATCH 49/53] netfilter: evict stale entries when user reads /proc/net/nf

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Message-Id: <1474844823-2026-50-git-send-email-pablo@netfilter.org>
Date:   Mon, 26 Sep 2016 01:06:59 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 49/53] netfilter: evict stale entries when user reads /proc/net/nf_conntrack

From: Florian Westphal <fw@...len.de>

Fabian reports a possible conntrack memory leak (could not reproduce so
far), however, one minor issue can be easily resolved:

> cat /proc/net/nf_conntrack | wc -l = 5
> 4 minutes required to clean up the table.

We should not report those timed-out entries to the user in first place.
And instead of just skipping those timed-out entries while iterating over
the table we can also zap them (we already do this during ctnetlink
walks, but I forgot about the /proc interface).

Fixes: f330a7fdbe16 ("netfilter: conntrack: get rid of conntrack timer")
Reported-by: Fabian Frederick <fabf@...net.be>
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_conntrack_standalone.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 7d52f8401afd..5f446cd9f3fd 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -212,6 +212,11 @@ static int ct_seq_show(struct seq_file *s, void *v)
 	if (unlikely(!atomic_inc_not_zero(&ct->ct_general.use)))
 		return 0;
 
+	if (nf_ct_should_gc(ct)) {
+		nf_ct_kill(ct);
+		goto release;
+	}
+
 	/* we only want to print DIR_ORIGINAL */
 	if (NF_CT_DIRECTION(hash))
 		goto release;
-- 
2.1.4