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Date:   Thu, 8 Dec 2022 16:43:24 -0800
From:   Saeed Mahameed <saeed@kernel.org>
To:     Gerhard Engleder <gerhard@engleder-embedded.com>
Cc:     netdev@vger.kernel.org, bpf@vger.kernel.org, davem@davemloft.net,
        kuba@kernel.org, edumazet@google.com, pabeni@redhat.com,
        ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org,
        john.fastabend@gmail.com
Subject: Re: [PATCH net-next v2 3/6] tsnep: Support XDP BPF program setup
Message-ID: <Y5KErK9c3Nafn45V@x130>
References: <20221208054045.3600-1-gerhard@engleder-embedded.com>
 <20221208054045.3600-4-gerhard@engleder-embedded.com>
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On 08 Dec 06:40, Gerhard Engleder wrote:
>Implement setup of BPF programs for XDP RX path with command
>XDP_SETUP_PROG of ndo_bpf(). This is prework for XDP RX path support.
>
>Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>

[ ... ]

>+int tsnep_xdp_setup_prog(struct tsnep_adapter *adapter, struct bpf_prog *prog,
>+			 struct netlink_ext_ack *extack)
>+{
>+	struct net_device *dev = adapter->netdev;
>+	bool if_running = netif_running(dev);
>+	struct bpf_prog *old_prog;
>+
>+	if (if_running)
>+		tsnep_netdev_close(dev);
>+
>+	old_prog = xchg(&adapter->xdp_prog, prog);
>+	if (old_prog)
>+		bpf_prog_put(old_prog);
>+
>+	if (if_running)
>+		tsnep_netdev_open(dev);

this could fail silently, and then cause double free, when close ndo 
will be called, the stack won't be aware of the closed state..