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From:   Felix Fietkau <nbd@nbd.name>
To:     netfilter-devel@vger.kernel.org,
        Pablo Neira Ayuso <pablo@netfilter.org>,
        Jozsef Kadlecsik <kadlec@netfilter.org>,
        Florian Westphal <fw@strlen.de>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
Cc:     coreteam@netfilter.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] netfilter: nf_flow_table: add missing locking
Date:   Mon, 21 Nov 2022 19:26:15 +0100
Message-Id: <20221121182615.90843-1-nbd@nbd.name>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

nf_flow_table_block_setup and the driver TC_SETUP_FT call can modify the flow
block cb list while they are being traversed elsewhere, causing a crash.
Add a write lock around the calls to protect readers

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/netfilter/nf_flow_table_offload.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index b04645ced89b..00b522890d77 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -1098,6 +1098,7 @@ static int nf_flow_table_block_setup(struct nf_flowtable *flowtable,
 	struct flow_block_cb *block_cb, *next;
 	int err = 0;
 
+	down_write(&flowtable->flow_block_lock);
 	switch (cmd) {
 	case FLOW_BLOCK_BIND:
 		list_splice(&bo->cb_list, &flowtable->flow_block.cb_list);
@@ -1112,6 +1113,7 @@ static int nf_flow_table_block_setup(struct nf_flowtable *flowtable,
 		WARN_ON_ONCE(1);
 		err = -EOPNOTSUPP;
 	}
+	up_write(&flowtable->flow_block_lock);
 
 	return err;
 }
@@ -1168,7 +1170,9 @@ static int nf_flow_table_offload_cmd(struct flow_block_offload *bo,
 
 	nf_flow_table_block_offload_init(bo, dev_net(dev), cmd, flowtable,
 					 extack);
+	down_write(&flowtable->flow_block_lock);
 	err = dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_FT, bo);
+	up_write(&flowtable->flow_block_lock);
 	if (err < 0)
 		return err;
 
-- 
2.38.1