linux-kernel - [PATCH net] net: hdlc_raw_eth: Clear the IFF_TX_SKB_SHARING flag after calling ether

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Date:   Mon, 19 Oct 2020 23:34:20 -0700
From:   Xie He <xie.he.0141@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Neil Horman <nhorman@...driver.com>,
        Krzysztof Halasa <khc@...waw.pl>
Cc:     Xie He <xie.he.0141@...il.com>
Subject: [PATCH net] net: hdlc_raw_eth: Clear the IFF_TX_SKB_SHARING flag after calling ether_setup

This driver calls ether_setup to set up the network device.
The ether_setup function would add the IFF_TX_SKB_SHARING flag to the
device. This flag indicates that it is safe to transmit shared skbs to
the device.

However, this is not true. This driver may pad the frame (in eth_tx)
before transmission, so the skb may be modified.

Cc: Neil Horman <nhorman@...driver.com>
Cc: Krzysztof Halasa <khc@...waw.pl>
Signed-off-by: Xie He <xie.he.0141@...il.com>
---
 drivers/net/wan/hdlc_raw_eth.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/wan/hdlc_raw_eth.c b/drivers/net/wan/hdlc_raw_eth.c
index 08e0a46501de..c70a518b8b47 100644
--- a/drivers/net/wan/hdlc_raw_eth.c
+++ b/drivers/net/wan/hdlc_raw_eth.c
@@ -99,6 +99,7 @@ static int raw_eth_ioctl(struct net_device *dev, struct ifreq *ifr)
 		old_qlen = dev->tx_queue_len;
 		ether_setup(dev);
 		dev->tx_queue_len = old_qlen;
+		dev->priv_flags &= ~IFF_TX_SKB_SHARING;
 		eth_hw_addr_random(dev);
 		call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
 		netif_dormant_off(dev);
-- 
2.25.1