net: introduce CAN specific pointer in the struct net_device

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@syzkaller.appspotmail.com
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@pengutronix.de>
Link: https://lore.kernel.org/r/20210223070127.4538-1-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 2 insertions, 32 deletions

diff --git a/net/can/af_can.c b/net/can/af_can.c
index 837bb8af0ec3..cce2af10eb3e 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_ml = can_get_ml_priv(dev);
+		return &can_ml->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);