ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 259 insertions, 0 deletions

diff --git a/drivers/net/ipvlan/ipvtap.c b/drivers/net/ipvlan/ipvtap.c
new file mode 100644
index 000000000..66c949d94
--- /dev/null
+++ b/drivers/net/ipvlan/ipvtap.c
@@ -0,0 +1,259 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/etherdevice.h>
+#include "ipvlan.h"
+#include <linux/if_vlan.h>
+#include <linux/if_tap.h>
+#include <linux/interrupt.h>
+#include <linux/nsproxy.h>
+#include <linux/compat.h>
+#include <linux/if_tun.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/cache.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+#include <linux/cdev.h>
+#include <linux/idr.h>
+#include <linux/fs.h>
+#include <linux/uio.h>
+
+#include <net/net_namespace.h>
+#include <net/rtnetlink.h>
+#include <net/sock.h>
+#include <linux/virtio_net.h>
+
+#define TUN_OFFLOADS (NETIF_F_HW_CSUM | NETIF_F_TSO_ECN | NETIF_F_TSO | \
+		      NETIF_F_TSO6)
+
+static dev_t ipvtap_major;
+static struct cdev ipvtap_cdev;
+
+static const struct ns_common *ipvtap_net_namespace(const struct device *d)
+{
+	const struct net_device *dev = to_net_dev(d->parent);
+
+	return to_ns_common(dev_net(dev));
+}
+
+static struct class ipvtap_class = {
+	 .name = "ipvtap",
+	 .ns_type = &net_ns_type_operations,
+	 .namespace = ipvtap_net_namespace,
+};
+
+struct ipvtap_dev {
+	struct ipvl_dev vlan;
+	struct tap_dev	  tap;
+};
+
+static void ipvtap_count_tx_dropped(struct tap_dev *tap)
+{
+	struct ipvtap_dev *vlantap = container_of(tap, struct ipvtap_dev, tap);
+	struct ipvl_dev *vlan = &vlantap->vlan;
+
+	this_cpu_inc(vlan->pcpu_stats->tx_drps);
+}
+
+static void ipvtap_count_rx_dropped(struct tap_dev *tap)
+{
+	struct ipvtap_dev *vlantap = container_of(tap, struct ipvtap_dev, tap);
+	struct ipvl_dev *vlan = &vlantap->vlan;
+
+	ipvlan_count_rx(vlan, 0, 0, 0);
+}
+
+static void ipvtap_update_features(struct tap_dev *tap,
+				   netdev_features_t features)
+{
+	struct ipvtap_dev *vlantap = container_of(tap, struct ipvtap_dev, tap);
+	struct ipvl_dev *vlan = &vlantap->vlan;
+
+	vlan->sfeatures = features;
+	netdev_update_features(vlan->dev);
+}
+
+static int ipvtap_newlink(struct net_device *dev,
+			  struct rtnl_newlink_params *params,
+			  struct netlink_ext_ack *extack)
+{
+	struct ipvtap_dev *vlantap = netdev_priv(dev);
+	int err;
+
+	INIT_LIST_HEAD(&vlantap->tap.queue_list);
+
+	/* Since macvlan supports all offloads by default, make
+	 * tap support all offloads also.
+	 */
+	vlantap->tap.tap_features = TUN_OFFLOADS;
+	vlantap->tap.count_tx_dropped = ipvtap_count_tx_dropped;
+	vlantap->tap.update_features =	ipvtap_update_features;
+	vlantap->tap.count_rx_dropped = ipvtap_count_rx_dropped;
+
+	err = netdev_rx_handler_register(dev, tap_handle_frame, &vlantap->tap);
+	if (err)
+		return err;
+
+	/* Don't put anything that may fail after macvlan_common_newlink
+	 * because we can't undo what it does.
+	 */
+	err = ipvlan_link_new(dev, params, extack);
+	if (err) {
+		netdev_rx_handler_unregister(dev);
+		return err;
+	}
+
+	vlantap->tap.dev = vlantap->vlan.dev;
+
+	return err;
+}
+
+static void __ipvtap_dellink(struct net *net, struct net_device *dev,
+			     struct list_head *head)
+{
+	struct ipvtap_dev *vlantap = netdev_priv(dev);
+
+	netdev_rx_handler_unregister(dev);
+	tap_del_queues(&vlantap->tap);
+	__ipvlan_link_delete(net, dev, head);
+}
+
+static void ipvtap_dellink(struct net_device *dev,
+			   struct list_head *head)
+{
+	struct ipvtap_dev *vlantap = netdev_priv(dev);
+	struct ipvl_port *port = vlantap->vlan.port;
+
+	mutex_lock(&port->pnodes_lock);
+	if (!vlantap->vlan.dying)
+		__ipvtap_dellink(dev_net(dev), dev, head);
+	mutex_unlock(&port->pnodes_lock);
+}
+
+static void ipvtap_setup(struct net_device *dev)
+{
+	ipvlan_link_setup(dev);
+	dev->tx_queue_len = TUN_READQ_SIZE;
+	dev->priv_flags &= ~IFF_NO_QUEUE;
+}
+
+static struct rtnl_link_ops ipvtap_link_ops __read_mostly = {
+	.kind		= "ipvtap",
+	.setup		= ipvtap_setup,
+	.newlink	= ipvtap_newlink,
+	.dellink	= ipvtap_dellink,
+	.priv_size	= sizeof(struct ipvtap_dev),
+};
+
+static int ipvtap_device_event(struct notifier_block *unused,
+			       unsigned long event, void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct ipvtap_dev *vlantap;
+	struct device *classdev;
+	dev_t devt;
+	int err;
+	char tap_name[IFNAMSIZ];
+
+	if (dev->rtnl_link_ops != &ipvtap_link_ops)
+		return NOTIFY_DONE;
+
+	snprintf(tap_name, IFNAMSIZ, "tap%d", dev->ifindex);
+	vlantap = netdev_priv(dev);
+
+	switch (event) {
+	case NETDEV_REGISTER:
+		/* Create the device node here after the network device has
+		 * been registered but before register_netdevice has
+		 * finished running.
+		 */
+		err = tap_get_minor(ipvtap_major, &vlantap->tap);
+		if (err)
+			return notifier_from_errno(err);
+
+		devt = MKDEV(MAJOR(ipvtap_major), vlantap->tap.minor);
+		classdev = device_create(&ipvtap_class, &dev->dev, devt,
+					 dev, "%s", tap_name);
+		if (IS_ERR(classdev)) {
+			tap_free_minor(ipvtap_major, &vlantap->tap);
+			return notifier_from_errno(PTR_ERR(classdev));
+		}
+		err = sysfs_create_link(&dev->dev.kobj, &classdev->kobj,
+					tap_name);
+		if (err)
+			return notifier_from_errno(err);
+		break;
+	case NETDEV_UNREGISTER:
+		/* vlan->minor == 0 if NETDEV_REGISTER above failed */
+		if (vlantap->tap.minor == 0)
+			break;
+		sysfs_remove_link(&dev->dev.kobj, tap_name);
+		devt = MKDEV(MAJOR(ipvtap_major), vlantap->tap.minor);
+		device_destroy(&ipvtap_class, devt);
+		tap_free_minor(ipvtap_major, &vlantap->tap);
+		break;
+	case NETDEV_CHANGE_TX_QUEUE_LEN:
+		if (tap_queue_resize(&vlantap->tap))
+			return NOTIFY_BAD;
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block ipvtap_notifier_block __read_mostly = {
+	.notifier_call	= ipvtap_device_event,
+};
+
+static int __init ipvtap_init(void)
+{
+	int err;
+
+	__ipvtap_dellink_ptr = __ipvtap_dellink;
+
+	err = tap_create_cdev(&ipvtap_cdev, &ipvtap_major, "ipvtap",
+			      THIS_MODULE);
+	if (err)
+		goto out1;
+
+	err = class_register(&ipvtap_class);
+	if (err)
+		goto out2;
+
+	err = register_netdevice_notifier(&ipvtap_notifier_block);
+	if (err)
+		goto out3;
+
+	err = ipvlan_link_register(&ipvtap_link_ops);
+	if (err)
+		goto out4;
+
+	return 0;
+
+out4:
+	unregister_netdevice_notifier(&ipvtap_notifier_block);
+out3:
+	class_unregister(&ipvtap_class);
+out2:
+	tap_destroy_cdev(ipvtap_major, &ipvtap_cdev);
+out1:
+	__ipvtap_dellink_ptr = NULL;
+
+	return err;
+}
+module_init(ipvtap_init);
+
+static void __exit ipvtap_exit(void)
+{
+	rtnl_link_unregister(&ipvtap_link_ops);
+	unregister_netdevice_notifier(&ipvtap_notifier_block);
+	class_unregister(&ipvtap_class);
+	tap_destroy_cdev(ipvtap_major, &ipvtap_cdev);
+	__ipvtap_dellink_ptr = NULL;
+}
+module_exit(ipvtap_exit);
+MODULE_ALIAS_RTNL_LINK("ipvtap");
+MODULE_AUTHOR("Sainath Grandhi <sainath.grandhi@intel.com>");
+MODULE_DESCRIPTION("IP-VLAN based tap driver");
+MODULE_LICENSE("GPL");