[RFC PATCH net 1/2] net: introduce CAN specific pointer in the struct net_device

From: Oleksij Rempel
Date: Fri Jan 15 2021 - 09:32:37 EST

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Since 20dd3850bcf8 ("can: Speed up CAN frame receiption by using
ml_priv") the CAN framework uses per device specific data in the AF_CAN
protocol. For this purpose the struct net_device->ml_priv is used. Later
the ml_priv usage in CAN was extended for other users, one of them being
CAN_J1939.

Later in the kernel ml_priv was converted to an union, used by other
drivers. E.g. the tun driver started storing it's stats pointer.

Since tun devices can claim to be a CAN device, CAN specific protocols
will wrongly interpret this pointer, which will cause system crashes.
Mostly this issue is visible in the CAN_J1939 stack.

To fix this issue, we request a dedicated CAN pointer within the
net_device struct.

Reported-by: syzbot+5138c4dd15a0401bec7b@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 20dd3850bcf8 ("can: Speed up CAN frame receiption by using ml_priv")
Fixes: ffd956eef69b ("can: introduce CAN midlayer private and allocate it automatically")
Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Fixes: 497a5757ce4e ("tun: switch to net core provided statistics counters")
Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
---
drivers/net/can/dev/dev.c | 2 +-
drivers/net/can/slcan.c | 2 +-
drivers/net/can/vcan.c | 2 +-
drivers/net/can/vxcan.c | 2 +-
include/linux/netdevice.h | 4 ++++
net/can/af_can.c | 4 ++--
net/can/j1939/main.c | 4 ++--
net/can/j1939/socket.c | 2 +-
net/can/proc.c | 13 +++++++------
9 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c
index f580f0ac6497..0e5265cb635f 100644
--- a/drivers/net/can/dev/dev.c
+++ b/drivers/net/can/dev/dev.c
@@ -269,7 +269,7 @@ struct net_device *alloc_candev_mqs(int sizeof_priv, unsigned int echo_skb_max,
priv = netdev_priv(dev);
priv->dev = dev;

- dev->ml_priv = (void *)priv + ALIGN(sizeof_priv, NETDEV_ALIGN);
+ dev->can = (void *)priv + ALIGN(sizeof_priv, NETDEV_ALIGN);

if (echo_skb_max) {
priv->echo_skb_max = echo_skb_max;
diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index a1bd1be09548..f703bd3b7415 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -538,7 +538,7 @@ static struct slcan *slc_alloc(void)

dev->base_addr = i;
sl = netdev_priv(dev);
- dev->ml_priv = (void *)sl + ALIGN(sizeof(*sl), NETDEV_ALIGN);
+ dev->can = (void *)sl + ALIGN(sizeof(*sl), NETDEV_ALIGN);

/* Initialize channel control data */
sl->magic = SLCAN_MAGIC;
diff --git a/drivers/net/can/vcan.c b/drivers/net/can/vcan.c
index 39ca14b0585d..d8c8f9cc769f 100644
--- a/drivers/net/can/vcan.c
+++ b/drivers/net/can/vcan.c
@@ -153,7 +153,7 @@ static void vcan_setup(struct net_device *dev)
dev->addr_len = 0;
dev->tx_queue_len = 0;
dev->flags = IFF_NOARP;
- dev->ml_priv = netdev_priv(dev);
+ dev->can = netdev_priv(dev);

/* set flags according to driver capabilities */
if (echo)
diff --git a/drivers/net/can/vxcan.c b/drivers/net/can/vxcan.c
index fa47bab510bb..0fea82935bf0 100644
--- a/drivers/net/can/vxcan.c
+++ b/drivers/net/can/vxcan.c
@@ -147,7 +147,7 @@ static void vxcan_setup(struct net_device *dev)
dev->flags = (IFF_NOARP|IFF_ECHO);
dev->netdev_ops = &vxcan_netdev_ops;
dev->needs_free_netdev = true;
- dev->ml_priv = netdev_priv(dev) + ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN);
+ dev->can = netdev_priv(dev) + ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN);
}

/* forward declaration for rtnl_create_link() */
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 5b949076ed23..825220da2e4f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2153,6 +2153,10 @@ struct net_device {

/* protected by rtnl_lock */
struct bpf_xdp_entity xdp_state[__MAX_XDP_MODE];
+
+#if IS_ENABLED(CONFIG_CAN)
+ struct can_ml_priv *can;
+#endif
};
#define to_net_dev(d) container_of(d, struct net_device, dev)

diff --git a/net/can/af_can.c b/net/can/af_can.c
index 837bb8af0ec3..8651c8112a65 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -304,7 +304,7 @@ static struct can_dev_rcv_lists *can_dev_rcv_lists_find(struct net *net,
struct net_device *dev)
{
if (dev) {
- struct can_ml_priv *ml_priv = dev->ml_priv;
+ struct can_ml_priv *ml_priv = dev->can;
return &ml_priv->dev_rcv_lists;
} else {
return net->can.rx_alldev_list;
@@ -801,7 +801,7 @@ static int can_notifier(struct notifier_block *nb, unsigned long msg,

switch (msg) {
case NETDEV_REGISTER:
- WARN(!dev->ml_priv,
+ WARN(!dev->can,
"No CAN mid layer private allocated, please fix your driver and use alloc_candev()!\n");
break;
}
diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
index bb914d8b4216..62088074230d 100644
--- a/net/can/j1939/main.c
+++ b/net/can/j1939/main.c
@@ -140,7 +140,7 @@ static struct j1939_priv *j1939_priv_create(struct net_device *ndev)
static inline void j1939_priv_set(struct net_device *ndev,
struct j1939_priv *priv)
{
- struct can_ml_priv *can_ml_priv = ndev->ml_priv;
+ struct can_ml_priv *can_ml_priv = ndev->can;

can_ml_priv->j1939_priv = priv;
}
@@ -211,7 +211,7 @@ static void __j1939_rx_release(struct kref *kref)
/* get pointer to priv without increasing ref counter */
static inline struct j1939_priv *j1939_ndev_to_priv(struct net_device *ndev)
{
- struct can_ml_priv *can_ml_priv = ndev->ml_priv;
+ struct can_ml_priv *can_ml_priv = ndev->can;

if (!can_ml_priv)
return NULL;
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index f23966526a88..8010fbc8bd29 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -467,7 +467,7 @@ static int j1939_sk_bind(struct socket *sock, struct sockaddr *uaddr, int len)
goto out_release_sock;
}

- if (!ndev->ml_priv) {
+ if (!ndev->can) {
netdev_warn_once(ndev,
"No CAN mid layer private allocated, please fix your driver and use alloc_candev()!\n");
dev_put(ndev);
diff --git a/net/can/proc.c b/net/can/proc.c
index 5ea8695f507e..7d7a7f6d2cc9 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -322,8 +322,9 @@ static int can_rcvlist_proc_show(struct seq_file *m, void *v)

/* receive list for registered CAN devices */
for_each_netdev_rcu(net, dev) {
- if (dev->type == ARPHRD_CAN && dev->ml_priv)
- can_rcvlist_proc_show_one(m, idx, dev, dev->ml_priv);
+ if (dev->type == ARPHRD_CAN && dev->can)
+ can_rcvlist_proc_show_one(m, idx, dev,
+ &dev->can->dev_rcv_lists);
}

rcu_read_unlock();
@@ -375,8 +376,8 @@ static int can_rcvlist_sff_proc_show(struct seq_file *m, void *v)

/* sff receive list for registered CAN devices */
for_each_netdev_rcu(net, dev) {
- if (dev->type == ARPHRD_CAN && dev->ml_priv) {
- dev_rcv_lists = dev->ml_priv;
+ if (dev->type == ARPHRD_CAN && dev->can) {
+ dev_rcv_lists = &dev->can->dev_rcv_lists;
can_rcvlist_proc_show_array(m, dev, dev_rcv_lists->rx_sff,
ARRAY_SIZE(dev_rcv_lists->rx_sff));
}
@@ -406,8 +407,8 @@ static int can_rcvlist_eff_proc_show(struct seq_file *m, void *v)

/* eff receive list for registered CAN devices */
for_each_netdev_rcu(net, dev) {
- if (dev->type == ARPHRD_CAN && dev->ml_priv) {
- dev_rcv_lists = dev->ml_priv;
+ if (dev->type == ARPHRD_CAN && dev->can) {
+ dev_rcv_lists = &dev->can->dev_rcv_lists;
can_rcvlist_proc_show_array(m, dev, dev_rcv_lists->rx_eff,
ARRAY_SIZE(dev_rcv_lists->rx_eff));
}
--
2.30.0

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Next in thread: Oleksij Rempel: "[RFC PATCH net 2/2] net: can: j1939: fix check for valid CAN devices"
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