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, 206 insertions, 0 deletions

diff --git a/drivers/md/dm-uevent.c b/drivers/md/dm-uevent.c
new file mode 100644
index 000000000..491738263
--- /dev/null
+++ b/drivers/md/dm-uevent.c
@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Device Mapper Uevent Support (dm-uevent)
+ *
+ * Copyright IBM Corporation, 2007
+ *	Author: Mike Anderson <andmike@linux.vnet.ibm.com>
+ */
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/kobject.h>
+#include <linux/dm-ioctl.h>
+#include <linux/export.h>
+
+#include "dm.h"
+#include "dm-uevent.h"
+
+#define DM_MSG_PREFIX "uevent"
+
+static const struct {
+	enum dm_uevent_type type;
+	enum kobject_action action;
+	char *name;
+} _dm_uevent_type_names[] = {
+	{DM_UEVENT_PATH_FAILED, KOBJ_CHANGE, "PATH_FAILED"},
+	{DM_UEVENT_PATH_REINSTATED, KOBJ_CHANGE, "PATH_REINSTATED"},
+};
+
+static struct kmem_cache *_dm_event_cache;
+
+struct dm_uevent {
+	struct mapped_device *md;
+	enum kobject_action action;
+	struct kobj_uevent_env ku_env;
+	struct list_head elist;
+	char name[DM_NAME_LEN];
+	char uuid[DM_UUID_LEN];
+};
+
+static void dm_uevent_free(struct dm_uevent *event)
+{
+	kmem_cache_free(_dm_event_cache, event);
+}
+
+static struct dm_uevent *dm_uevent_alloc(struct mapped_device *md)
+{
+	struct dm_uevent *event;
+
+	event = kmem_cache_zalloc(_dm_event_cache, GFP_ATOMIC);
+	if (!event)
+		return NULL;
+
+	INIT_LIST_HEAD(&event->elist);
+	event->md = md;
+
+	return event;
+}
+
+static struct dm_uevent *dm_build_path_uevent(struct mapped_device *md,
+					      struct dm_target *ti,
+					      enum kobject_action action,
+					      const char *dm_action,
+					      const char *path,
+					      unsigned int nr_valid_paths)
+{
+	struct dm_uevent *event;
+
+	event = dm_uevent_alloc(md);
+	if (!event) {
+		DMERR("%s: dm_uevent_alloc() failed", __func__);
+		goto err_nomem;
+	}
+
+	event->action = action;
+
+	if (add_uevent_var(&event->ku_env, "DM_TARGET=%s", ti->type->name)) {
+		DMERR("%s: add_uevent_var() for DM_TARGET failed",
+		      __func__);
+		goto err_add;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_ACTION=%s", dm_action)) {
+		DMERR("%s: add_uevent_var() for DM_ACTION failed",
+		      __func__);
+		goto err_add;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_SEQNUM=%u",
+			   dm_next_uevent_seq(md))) {
+		DMERR("%s: add_uevent_var() for DM_SEQNUM failed",
+		      __func__);
+		goto err_add;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_PATH=%s", path)) {
+		DMERR("%s: add_uevent_var() for DM_PATH failed", __func__);
+		goto err_add;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_NR_VALID_PATHS=%d",
+			   nr_valid_paths)) {
+		DMERR("%s: add_uevent_var() for DM_NR_VALID_PATHS failed",
+		      __func__);
+		goto err_add;
+	}
+
+	return event;
+
+err_add:
+	dm_uevent_free(event);
+err_nomem:
+	return ERR_PTR(-ENOMEM);
+}
+
+/**
+ * dm_send_uevents - send uevents for given list
+ *
+ * @events:	list of events to send
+ * @kobj:	kobject generating event
+ *
+ */
+void dm_send_uevents(struct list_head *events, struct kobject *kobj)
+{
+	int r;
+	struct dm_uevent *event, *next;
+
+	list_for_each_entry_safe(event, next, events, elist) {
+		list_del_init(&event->elist);
+
+		/*
+		 * When a device is being removed this copy fails and we
+		 * discard these unsent events.
+		 */
+		if (dm_copy_name_and_uuid(event->md, event->name,
+					  event->uuid)) {
+			DMINFO("%s: skipping sending uevent for lost device",
+			       __func__);
+			goto uevent_free;
+		}
+
+		if (add_uevent_var(&event->ku_env, "DM_NAME=%s", event->name)) {
+			DMERR("%s: add_uevent_var() for DM_NAME failed",
+			      __func__);
+			goto uevent_free;
+		}
+
+		if (add_uevent_var(&event->ku_env, "DM_UUID=%s", event->uuid)) {
+			DMERR("%s: add_uevent_var() for DM_UUID failed",
+			      __func__);
+			goto uevent_free;
+		}
+
+		r = kobject_uevent_env(kobj, event->action, event->ku_env.envp);
+		if (r)
+			DMERR("%s: kobject_uevent_env failed", __func__);
+uevent_free:
+		dm_uevent_free(event);
+	}
+}
+EXPORT_SYMBOL_GPL(dm_send_uevents);
+
+/**
+ * dm_path_uevent - called to create a new path event and queue it
+ *
+ * @event_type:	path event type enum
+ * @ti:			pointer to a dm_target
+ * @path:		string containing pathname
+ * @nr_valid_paths:	number of valid paths remaining
+ *
+ */
+void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
+		   const char *path, unsigned int nr_valid_paths)
+{
+	struct mapped_device *md = dm_table_get_md(ti->table);
+	struct dm_uevent *event;
+
+	if (event_type >= ARRAY_SIZE(_dm_uevent_type_names)) {
+		DMERR("%s: Invalid event_type %d", __func__, event_type);
+		return;
+	}
+
+	event = dm_build_path_uevent(md, ti,
+				     _dm_uevent_type_names[event_type].action,
+				     _dm_uevent_type_names[event_type].name,
+				     path, nr_valid_paths);
+	if (IS_ERR(event))
+		return;
+
+	dm_uevent_add(md, &event->elist);
+}
+EXPORT_SYMBOL_GPL(dm_path_uevent);
+
+int dm_uevent_init(void)
+{
+	_dm_event_cache = KMEM_CACHE(dm_uevent, 0);
+	if (!_dm_event_cache)
+		return -ENOMEM;
+
+	DMINFO("version 1.0.3");
+
+	return 0;
+}
+
+void dm_uevent_exit(void)
+{
+	kmem_cache_destroy(_dm_event_cache);
+}