From: Xie He xie.he.0141@gmail.com
[ Upstream commit 01c4ceae0a38a0bdbfea6896f41efcd985a9c064 ]
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: 1da177e4c3f4 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/wan/hdlc.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
--- a/drivers/net/wan/hdlc.c +++ b/drivers/net/wan/hdlc.c @@ -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);