Commit 01c4ceae authored Oct 19, 2020 by Xie He Committed by Jakub Kicinski Oct 21, 2020

net: hdlc: In hdlc_rcv, check to make sure dev is an HDLC device



The hdlc_rcv function is used as hdlc_packet_type.func to process any
skb received in the kernel with skb->protocol == htons(ETH_P_HDLC).
The purpose of this function is to provide second-stage processing for
skbs not assigned a "real" L3 skb->protocol value in the first stage.

This function assumes the device from which the skb is received is an
HDLC device (a device created by this module). It assumes that
netdev_priv(dev) returns a pointer to "struct hdlc_device".

However, it is possible that some driver in the kernel (not necessarily
in our control) submits a received skb with skb->protocol ==
htons(ETH_P_HDLC), from a non-HDLC device. In this case, the skb would
still be received by hdlc_rcv. This will cause problems.

hdlc_rcv should be able to recognize and drop invalid skbs. It should
first make sure "dev" is actually an HDLC device, before starting its
processing. This patch adds this check to hdlc_rcv.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Cc: Krzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
Link: https://lore.kernel.org/r/20201020013152.89259-1-xie.he.0141@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>

parent 0ed37ac5

drivers/net/wan/hdlc.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -46,7 +46,15 @@ static struct hdlc_proto *first_proto;
		static int hdlc_rcv(struct sk_buff skb, struct net_device dev,
		struct packet_type p, struct net_device orig_dev)
		{
		struct hdlc_device *hdlc = dev_to_hdlc(dev);
		struct hdlc_device *hdlc;

		/* First make sure "dev" is an HDLC device */
		if (!(dev->priv_flags & IFF_WAN_HDLC)) {
		kfree_skb(skb);
		return NET_RX_SUCCESS;
		}

		hdlc = dev_to_hdlc(dev);

		if (!net_eq(dev_net(dev), &init_net)) {
		kfree_skb(skb);

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