Commit c79f428d authored Aug 08, 2020 by Xie He Committed by David S. Miller Aug 11, 2020

drivers/net/wan/x25_asy: Added needed_headroom and a skb->len check



1. Added a skb->len check

This driver expects upper layers to include a pseudo header of 1 byte
when passing down a skb for transmission. This driver will read this
1-byte header. This patch added a skb->len check before reading the
header to make sure the header exists.

2. Added needed_headroom

When this driver transmits data,
  first this driver will remove a pseudo header of 1 byte,
  then the lapb module will prepend the LAPB header of 2 or 3 bytes.
So the value of needed_headroom in this driver should be 3 - 1.

Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent b06c19d9

drivers/net/wan/x25_asy.c

+14 −0

Original line number	Diff line number	Diff line
		@@ -307,6 +307,14 @@ static netdev_tx_t x25_asy_xmit(struct sk_buff *skb,
		return NETDEV_TX_OK;
		}

		/* There should be a pseudo header of 1 byte added by upper layers.
		* Check to make sure it is there before reading it.
		*/
		if (skb->len < 1) {
		kfree_skb(skb);
		return NETDEV_TX_OK;
		}

		switch (skb->data[0]) {
		case X25_IFACE_DATA:
		break;
		@@ -752,6 +760,12 @@ static void x25_asy_setup(struct net_device *dev)
		dev->type = ARPHRD_X25;
		dev->tx_queue_len = 10;

		/* When transmitting data:
		* first this driver removes a pseudo header of 1 byte,
		* then the lapb module prepends an LAPB header of at most 3 bytes.
		*/
		dev->needed_headroom = 3 - 1;

		/* New-style flags. */
		dev->flags = IFF_NOARP;
		}

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