[RFC PATCH net v2] net: introduce CAN specific pointer in the struct net_device

From: Oleksij Rempel
Date: Fri Feb 12 2021 - 08:11:04 EST

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 | 4 +++-
drivers/net/can/slcan.c | 4 +++-
drivers/net/can/vcan.c | 2 +-
drivers/net/can/vxcan.c | 6 +++++-
include/linux/can/can-ml.h | 12 ++++++++++++
include/linux/netdevice.h | 35 +++++++++++++++++++++++++++++++++++
net/can/af_can.c | 34 ++--------------------------------
net/can/j1939/main.c | 22 ++++++++--------------
net/can/j1939/socket.c | 13 ++++---------
net/can/proc.c | 19 +++++++++++++------
10 files changed, 86 insertions(+), 65 deletions(-)

diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c
index d9281ae853f8..912401788d93 100644
--- a/drivers/net/can/dev/dev.c
+++ b/drivers/net/can/dev/dev.c
@@ -239,6 +239,7 @@ void can_setup(struct net_device *dev)
struct net_device *alloc_candev_mqs(int sizeof_priv, unsigned int echo_skb_max,
unsigned int txqs, unsigned int rxqs)
{
+ struct can_ml_priv *can;
struct net_device *dev;
struct can_priv *priv;
int size;
@@ -270,7 +271,8 @@ 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);
+ can = (void *)priv + ALIGN(sizeof_priv, NETDEV_ALIGN);
+ can_set_ml_priv(dev, can);

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..135a4b929595 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -516,6 +516,7 @@ static struct slcan *slc_alloc(void)
int i;
char name[IFNAMSIZ];
struct net_device *dev = NULL;
+ struct can_ml_priv *can;
struct slcan *sl;
int size;

@@ -538,7 +539,8 @@ static struct slcan *slc_alloc(void)

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

/* Initialize channel control data */
sl->magic = SLCAN_MAGIC;
diff --git a/drivers/net/can/vcan.c b/drivers/net/can/vcan.c
index 39ca14b0585d..067705e2850b 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);
+ can_set_ml_priv(dev, 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 f9a524c5f6d6..81f2369f5a4a 100644
--- a/drivers/net/can/vxcan.c
+++ b/drivers/net/can/vxcan.c
@@ -141,6 +141,8 @@ static const struct net_device_ops vxcan_netdev_ops = {

static void vxcan_setup(struct net_device *dev)
{
+ struct can_ml_priv *can;
+
dev->type = ARPHRD_CAN;
dev->mtu = CANFD_MTU;
dev->hard_header_len = 0;
@@ -149,7 +151,9 @@ 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);
+
+ can = netdev_priv(dev) + ALIGN(sizeof(struct vxcan_priv), NETDEV_ALIGN);
+ can_set_ml_priv(dev, can);
}

/* forward declaration for rtnl_create_link() */
diff --git a/include/linux/can/can-ml.h b/include/linux/can/can-ml.h
index 2f5d731ae251..8afa92d15a66 100644
--- a/include/linux/can/can-ml.h
+++ b/include/linux/can/can-ml.h
@@ -44,6 +44,7 @@

#include <linux/can.h>
#include <linux/list.h>
+#include <linux/netdevice.h>

#define CAN_SFF_RCV_ARRAY_SZ (1 << CAN_SFF_ID_BITS)
#define CAN_EFF_RCV_HASH_BITS 10
@@ -65,4 +66,15 @@ struct can_ml_priv {
#endif
};

+static inline struct can_ml_priv *can_get_ml_priv(struct net_device *dev)
+{
+ return netdev_get_ml_priv(dev, ML_PRIV_CAN);
+}
+
+static inline void can_set_ml_priv(struct net_device *dev,
+ struct can_ml_priv *ml_priv)
+{
+ netdev_set_ml_priv(dev, ml_priv, ML_PRIV_CAN);
+}
+
#endif /* CAN_ML_H */
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index bfadf3b82f9c..9a4c6d14098c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1584,6 +1584,16 @@ enum netdev_priv_flags {
#define IFF_L3MDEV_RX_HANDLER IFF_L3MDEV_RX_HANDLER
#define IFF_LIVE_RENAME_OK IFF_LIVE_RENAME_OK

+/**
+ * enum netdev_ml_priv_type - &struct net_device ml_priv_type
+ *
+ * This enum specifies the type of the struct net_device::ml_priv pointer.
+ */
+enum netdev_ml_priv_type {
+ ML_PRIV_NONE,
+ ML_PRIV_CAN,
+};
+
/**
* struct net_device - The DEVICE structure.
*
@@ -1779,6 +1789,7 @@ enum netdev_priv_flags {
* @nd_net: Network namespace this network device is inside
*
* @ml_priv: Mid-layer private
+ @ml_priv_type: Mid-layer private type
* @lstats: Loopback statistics
* @tstats: Tunnel statistics
* @dstats: Dummy statistics
@@ -2100,6 +2111,7 @@ struct net_device {
struct pcpu_sw_netstats __percpu *tstats;
struct pcpu_dstats __percpu *dstats;
};
+ enum netdev_ml_priv_type ml_priv_type;

#if IS_ENABLED(CONFIG_GARP)
struct garp_port __rcu *garp_port;
@@ -2286,6 +2298,29 @@ static inline void netdev_reset_rx_headroom(struct net_device *dev)
netdev_set_rx_headroom(dev, -1);
}

+static inline void *netdev_get_ml_priv(struct net_device *dev,
+ enum netdev_ml_priv_type type)
+{
+ if (dev->ml_priv_type != type)
+ return NULL;
+
+ return dev->ml_priv;
+}
+
+static inline void netdev_set_ml_priv(struct net_device *dev,
+ void *ml_priv,
+ enum netdev_ml_priv_type type)
+{
+ WARN_ONCE(dev->ml_priv_type && dev->ml_priv_type != type,
+ "Overwriting already set ml_priv_type (%u) with different ml_priv_type (%u)!\n",
+ dev->ml_priv_type, type);
+ WARN_ONCE(!dev->ml_priv_type && dev->ml_priv,
+ "Overwriting already set ml_priv and ml_priv_type is ML_PRIV_NONE!\n");
+
+ dev->ml_priv = ml_priv;
+ dev->ml_priv_type = type;
+}
+
/*
* Net namespace inlines
*/
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 837bb8af0ec3..36263da24481 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -304,8 +304,8 @@ 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;
- return &ml_priv->dev_rcv_lists;
+ struct can_ml_priv *can = can_get_ml_priv(dev);
+ return &can->dev_rcv_lists;
} else {
return net->can.rx_alldev_list;
}
@@ -790,25 +790,6 @@ void can_proto_unregister(const struct can_proto *cp)
}
EXPORT_SYMBOL(can_proto_unregister);

-/* af_can notifier to create/remove CAN netdevice specific structs */
-static int can_notifier(struct notifier_block *nb, unsigned long msg,
- void *ptr)
-{
- struct net_device *dev = netdev_notifier_info_to_dev(ptr);
-
- if (dev->type != ARPHRD_CAN)
- return NOTIFY_DONE;
-
- switch (msg) {
- case NETDEV_REGISTER:
- WARN(!dev->ml_priv,
- "No CAN mid layer private allocated, please fix your driver and use alloc_candev()!\n");
- break;
- }
-
- return NOTIFY_DONE;
-}
-
static int can_pernet_init(struct net *net)
{
spin_lock_init(&net->can.rcvlists_lock);
@@ -876,11 +857,6 @@ static const struct net_proto_family can_family_ops = {
.owner = THIS_MODULE,
};

-/* notifier block for netdevice event */
-static struct notifier_block can_netdev_notifier __read_mostly = {
- .notifier_call = can_notifier,
-};
-
static struct pernet_operations can_pernet_ops __read_mostly = {
.init = can_pernet_init,
.exit = can_pernet_exit,
@@ -911,17 +887,12 @@ static __init int can_init(void)
err = sock_register(&can_family_ops);
if (err)
goto out_sock;
- err = register_netdevice_notifier(&can_netdev_notifier);
- if (err)
- goto out_notifier;

dev_add_pack(&can_packet);
dev_add_pack(&canfd_packet);

return 0;

-out_notifier:
- sock_unregister(PF_CAN);
out_sock:
unregister_pernet_subsys(&can_pernet_ops);
out_pernet:
@@ -935,7 +906,6 @@ static __exit void can_exit(void)
/* protocol unregister */
dev_remove_pack(&canfd_packet);
dev_remove_pack(&can_packet);
- unregister_netdevice_notifier(&can_netdev_notifier);
sock_unregister(PF_CAN);

unregister_pernet_subsys(&can_pernet_ops);
diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
index bb914d8b4216..7eaf1df09f5b 100644
--- a/net/can/j1939/main.c
+++ b/net/can/j1939/main.c
@@ -140,9 +140,9 @@ 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 = can_get_ml_priv(ndev);

- can_ml_priv->j1939_priv = priv;
+ can->j1939_priv = priv;
}

static void __j1939_priv_release(struct kref *kref)
@@ -211,12 +211,9 @@ 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 = can_get_ml_priv(ndev);

- if (!can_ml_priv)
- return NULL;
-
- return can_ml_priv->j1939_priv;
+ return can->j1939_priv;
}

static struct j1939_priv *j1939_priv_get_by_ndev_locked(struct net_device *ndev)
@@ -225,9 +222,6 @@ static struct j1939_priv *j1939_priv_get_by_ndev_locked(struct net_device *ndev)

lockdep_assert_held(&j1939_netdev_lock);

- if (ndev->type != ARPHRD_CAN)
- return NULL;
-
priv = j1939_ndev_to_priv(ndev);
if (priv)
j1939_priv_get(priv);
@@ -348,15 +342,16 @@ static int j1939_netdev_notify(struct notifier_block *nb,
unsigned long msg, void *data)
{
struct net_device *ndev = netdev_notifier_info_to_dev(data);
+ struct can_ml_priv *can = can_get_ml_priv(ndev);
struct j1939_priv *priv;

+ if (!can)
+ goto notify_done;
+
priv = j1939_priv_get_by_ndev(ndev);
if (!priv)
goto notify_done;

- if (ndev->type != ARPHRD_CAN)
- goto notify_put;
-
switch (msg) {
case NETDEV_DOWN:
j1939_cancel_active_session(priv, NULL);
@@ -365,7 +360,6 @@ static int j1939_netdev_notify(struct notifier_block *nb,
break;
}

-notify_put:
j1939_priv_put(priv);

notify_done:
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index f23966526a88..2ccba2dc5bd8 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -12,6 +12,7 @@

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+#include <linux/can/can-ml.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/errqueue.h>
@@ -454,6 +455,7 @@ static int j1939_sk_bind(struct socket *sock, struct sockaddr *uaddr, int len)
j1939_local_ecu_put(priv, jsk->addr.src_name, jsk->addr.sa);
} else {
struct net_device *ndev;
+ struct can_ml_priv *can;

ndev = dev_get_by_index(net, addr->can_ifindex);
if (!ndev) {
@@ -461,15 +463,8 @@ static int j1939_sk_bind(struct socket *sock, struct sockaddr *uaddr, int len)
goto out_release_sock;
}

- if (ndev->type != ARPHRD_CAN) {
- dev_put(ndev);
- ret = -ENODEV;
- goto out_release_sock;
- }
-
- if (!ndev->ml_priv) {
- netdev_warn_once(ndev,
- "No CAN mid layer private allocated, please fix your driver and use alloc_candev()!\n");
+ can = can_get_ml_priv(ndev);
+ if (!can) {
dev_put(ndev);
ret = -ENODEV;
goto out_release_sock;
diff --git a/net/can/proc.c b/net/can/proc.c
index 5ea8695f507e..4138623e4c58 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -322,8 +322,11 @@ 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);
+ struct can_ml_priv *can = can_get_ml_priv(dev);
+
+ if (can)
+ can_rcvlist_proc_show_one(m, idx, dev,
+ &can->dev_rcv_lists);
}

rcu_read_unlock();
@@ -375,8 +378,10 @@ 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;
+ struct can_ml_priv *can = can_get_ml_priv(dev);
+
+ if (can) {
+ dev_rcv_lists = &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 +411,10 @@ 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;
+ struct can_ml_priv *can = can_get_ml_priv(dev);
+
+ if (can) {
+ dev_rcv_lists = &can->dev_rcv_lists;
can_rcvlist_proc_show_array(m, dev, dev_rcv_lists->rx_eff,
ARRAY_SIZE(dev_rcv_lists->rx_eff));
}
--
2.29.2