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(p200300ea8f232800e1135d8d7b96ca98.dip0.t-ipconnect.de. [2003:ea:8f23:2800:e113:5d8d:7b96:ca98]) by smtp.googlemail.com with ESMTPSA id m27sm3051455eji.64.2020.11.12.23.46.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Nov 2020 23:46:56 -0800 (PST) Subject: Re: [PATCH 2/3] net: openvswitch: use core API for updating TX stats To: Lev Stipakov , Pravin B Shelar , "David S. Miller" , Jakub Kicinski , netdev@vger.kernel.org, dev@openvswitch.org, linux-kernel@vger.kernel.org Cc: Lev Stipakov References: <20201112111150.34361-1-lev@openvpn.net> From: Heiner Kallweit Message-ID: <598c779c-fb0b-a9a6-43be-3a7cd5b38946@gmail.com> Date: Fri, 13 Nov 2020 08:40:42 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.3 MIME-Version: 1.0 In-Reply-To: <20201112111150.34361-1-lev@openvpn.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 12.11.2020 um 12:11 schrieb Lev Stipakov: > Commit d3fd65484c781 ("net: core: add dev_sw_netstats_tx_add") has added > function "dev_sw_netstats_tx_add()" to update net device per-cpu TX > stats. > > Use this function instead of own code. While on it, replace > "len" variable with "skb->len". > Using dev_sw_netstats_tx_add() is fine, however you have to keep variable len, see remark in the code. In addition you can replace internal_get_stats() with dev_get_tstats64(). > Signed-off-by: Lev Stipakov > --- > net/openvswitch/vport-internal_dev.c | 16 +++++----------- > 1 file changed, 5 insertions(+), 11 deletions(-) > > diff --git a/net/openvswitch/vport-internal_dev.c b/net/openvswitch/vport-internal_dev.c > index 1e30d8df3ba5..116738d36e02 100644 > --- a/net/openvswitch/vport-internal_dev.c > +++ b/net/openvswitch/vport-internal_dev.c > @@ -33,23 +33,17 @@ static struct internal_dev *internal_dev_priv(struct net_device *netdev) > static netdev_tx_t > internal_dev_xmit(struct sk_buff *skb, struct net_device *netdev) > { > - int len, err; > + int err; > > - len = skb->len; > rcu_read_lock(); > err = ovs_vport_receive(internal_dev_priv(netdev)->vport, skb, NULL); We would have a well-hidden problem here. ovs_vport_receive() calls function ovs_dp_process_packet() that frees the skb under certain circumstances. Note that the skb can be freed even if ovs_vport_receive() returns OK. Using skb->len after calling ovs_vport_receive() could result in a use-after-free therefore. So you have to keep variable len. > rcu_read_unlock(); > > - if (likely(!err)) { > - struct pcpu_sw_netstats *tstats = this_cpu_ptr(netdev->tstats); > - > - u64_stats_update_begin(&tstats->syncp); > - tstats->tx_bytes += len; > - tstats->tx_packets++; > - u64_stats_update_end(&tstats->syncp); > - } else { > + if (likely(!err)) > + dev_sw_netstats_tx_add(netdev, 1, skb->len); > + else > netdev->stats.tx_errors++; > - } > + > return NETDEV_TX_OK; > } > >