From 500f00bc732baf1f96bdc6b546a60bb07aedfdc1 Mon Sep 17 00:00:00 2001
From: Xie He <xie.he.0141@gmail.com>
Date: Mon, 19 Oct 2020 18:31:52 -0700
Subject: [PATCH 1/4] net: hdlc: In hdlc_rcv, check to make sure dev is an HDLC
device
Git-commit: 01c4ceae0a38a0bdbfea6896f41efcd985a9c064
References: git-fixes
Patch-mainline: v5.10-rc1
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: Denis Kirjanov <denis.kirjanov@suse.com>
---
drivers/net/wan/hdlc.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/net/wan/hdlc.c b/drivers/net/wan/hdlc.c
index 7221a53b8b14..500463044b1a 100644
--- a/drivers/net/wan/hdlc.c
+++ b/drivers/net/wan/hdlc.c
@@ -49,7 +49,15 @@ 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);
--
2.16.4