From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	=?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= <Jeremy.Jean@oss.cyber.gouv.fr>,
	Pablo Neira Ayuso <pablo@netfilter.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18 180/217] netfilter: flowtable: publish GC-visible tuple last
Date: Thu, 20 Aug 2026 16:55:48 +0200
Message-ID: <20260820145243.151110951@linuxfoundation.org>
In-Reply-To: <20260820145237.531699751@linuxfoundation.org>
References: <20260820145237.531699751@linuxfoundation.org>
User-Agent: quilt/0.69
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

6.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>

[ Upstream commit 2014ac62df9d45bb9a004a043e85df7be09ed780 ]

nf_flow_table_iterate() only treats original-direction tuple nodes as
owning entries. Publishing the original node first lets GC observe and
free a flow while flow_offload_add() is still inserting the reply node.
Publish the reply node first and the original node last so GC never
sees a partially installed flow.

KASAN can trigger slab-use-after-free read and write reports in the
flowtable/rhashtable path (rht_deferred_worker, jhash, flow_offload_del,
flow_offload_lookup, etc.).

Fixes: ac2a66665e23 ("netfilter: add generic flow table infrastructure")
Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
Assisted-by: Codex:gpt-5
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/netfilter/nf_flow_table_core.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 595a0f19d15e7..7a93e22d049db 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -324,17 +324,18 @@ int flow_offload_add(struct nf_flowtable *flow_table, struct flow_offload *flow)
 	flow->timeout = nf_flowtable_time_stamp + flow_offload_get_timeout(flow);
 
 	err = rhashtable_insert_fast(&flow_table->rhashtable,
-				     &flow->tuplehash[0].node,
+				     &flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].node,
 				     nf_flow_offload_rhash_params);
 	if (err < 0)
 		return err;
 
+	/* GC only iterates original-direction entries; publish original last. */
 	err = rhashtable_insert_fast(&flow_table->rhashtable,
-				     &flow->tuplehash[1].node,
+				     &flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].node,
 				     nf_flow_offload_rhash_params);
 	if (err < 0) {
 		rhashtable_remove_fast(&flow_table->rhashtable,
-				       &flow->tuplehash[0].node,
+				       &flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].node,
 				       nf_flow_offload_rhash_params);
 		return err;
 	}
-- 
2.53.0