netdev - [PATCH nf] netfilter: nf_conntrack: do not skip entries in /proc/net/nf

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Message-ID: <20250924072709.2891285-1-edumazet@google.com>
Date: Wed, 24 Sep 2025 07:27:09 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Pablo Neira Ayuso <pablo@...filter.org>, Florian Westphal <fw@...len.de>, 
	Jozsef Kadlecsik <kadlec@...filter.org>
Cc: netdev@...r.kernel.org, netfilter-devel@...r.kernel.org, 
	coreteam@...filter.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH nf] netfilter: nf_conntrack: do not skip entries in /proc/net/nf_conntrack

ct_seq_show() has an opportunistic garbage collector :

if (nf_ct_should_gc(ct)) {
    nf_ct_kill(ct);
    goto release;
}

So if one nf_conn is killed there, next time ct_get_next() runs,
we skip the following item in the bucket, even if it should have
been displayed if gc did not take place.

We can decrement st->skip_elems to tell ct_get_next() one of the items
was removed from the chain.

Fixes: 58e207e4983d ("netfilter: evict stale entries when user reads /proc/net/nf_conntrack")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/netfilter/nf_conntrack_standalone.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 1f14ef0436c65fccc8e64956a105d5473e21b55e..708b79380f047f32aa8e6047c52c807b4019f2b9 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -317,6 +317,9 @@ static int ct_seq_show(struct seq_file *s, void *v)
 	smp_acquire__after_ctrl_dep();
 
 	if (nf_ct_should_gc(ct)) {
+		struct ct_iter_state *st = s->private;
+
+		st->skip_elems--;
 		nf_ct_kill(ct);
 		goto release;
 	}
-- 
2.51.0.534.gc79095c0ca-goog