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, 311 insertions, 0 deletions

diff --git a/lib/plist.c b/lib/plist.c
new file mode 100644
index 000000000..a5bef38ad
--- /dev/null
+++ b/lib/plist.c
@@ -0,0 +1,311 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * lib/plist.c
+ *
+ * Descending-priority-sorted double-linked list
+ *
+ * (C) 2002-2003 Intel Corp
+ * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
+ *
+ * 2001-2005 (c) MontaVista Software, Inc.
+ * Daniel Walker <dwalker@mvista.com>
+ *
+ * (C) 2005 Linutronix GmbH, Thomas Gleixner <tglx@kernel.org>
+ *
+ * Simplifications of the original code by
+ * Oleg Nesterov <oleg@tv-sign.ru>
+ *
+ * Based on simple lists (include/linux/list.h).
+ *
+ * This file contains the add / del functions which are considered to
+ * be too large to inline. See include/linux/plist.h for further
+ * information.
+ */
+
+#include <linux/bug.h>
+#include <linux/plist.h>
+
+#ifdef CONFIG_DEBUG_PLIST
+
+static struct plist_head test_head;
+
+static void plist_check_prev_next(struct list_head *t, struct list_head *p,
+				  struct list_head *n)
+{
+	WARN(n->prev != p || p->next != n,
+			"top: %p, n: %p, p: %p\n"
+			"prev: %p, n: %p, p: %p\n"
+			"next: %p, n: %p, p: %p\n",
+			 t, t->next, t->prev,
+			p, p->next, p->prev,
+			n, n->next, n->prev);
+}
+
+static void plist_check_list(struct list_head *top)
+{
+	struct list_head *prev = top, *next = top->next;
+
+	plist_check_prev_next(top, prev, next);
+	while (next != top) {
+		prev = next;
+		next = prev->next;
+		plist_check_prev_next(top, prev, next);
+	}
+}
+
+static void plist_check_head(struct plist_head *head)
+{
+	if (!plist_head_empty(head))
+		plist_check_list(&plist_first(head)->prio_list);
+	plist_check_list(&head->node_list);
+}
+
+#else
+# define plist_check_head(h)	do { } while (0)
+#endif
+
+/**
+ * plist_add - add @node to @head
+ *
+ * @node:	&struct plist_node pointer
+ * @head:	&struct plist_head pointer
+ */
+void plist_add(struct plist_node *node, struct plist_head *head)
+{
+	struct plist_node *first, *iter, *prev = NULL, *last, *reverse_iter;
+	struct list_head *node_next = &head->node_list;
+
+	plist_check_head(head);
+	WARN_ON(!plist_node_empty(node));
+	WARN_ON(!list_empty(&node->prio_list));
+
+	if (plist_head_empty(head))
+		goto ins_node;
+
+	first = iter = plist_first(head);
+	last = reverse_iter = list_entry(first->prio_list.prev, struct plist_node, prio_list);
+
+	do {
+		if (node->prio < iter->prio) {
+			node_next = &iter->node_list;
+			break;
+		} else if (node->prio >= reverse_iter->prio) {
+			prev = reverse_iter;
+			iter = list_entry(reverse_iter->prio_list.next,
+				struct plist_node, prio_list);
+			if (likely(reverse_iter != last))
+				node_next = &iter->node_list;
+			break;
+		}
+
+		prev = iter;
+		iter = list_entry(iter->prio_list.next,
+				struct plist_node, prio_list);
+		reverse_iter = list_entry(reverse_iter->prio_list.prev,
+				struct plist_node, prio_list);
+	} while (iter != first);
+
+	if (!prev || prev->prio != node->prio)
+		list_add_tail(&node->prio_list, &iter->prio_list);
+ins_node:
+	list_add_tail(&node->node_list, node_next);
+
+	plist_check_head(head);
+}
+
+/**
+ * plist_del - Remove a @node from plist.
+ *
+ * @node:	&struct plist_node pointer - entry to be removed
+ * @head:	&struct plist_head pointer - list head
+ */
+void plist_del(struct plist_node *node, struct plist_head *head)
+{
+	plist_check_head(head);
+
+	if (!list_empty(&node->prio_list)) {
+		if (node->node_list.next != &head->node_list) {
+			struct plist_node *next;
+
+			next = list_entry(node->node_list.next,
+					struct plist_node, node_list);
+
+			/* add the next plist_node into prio_list */
+			if (list_empty(&next->prio_list))
+				list_add(&next->prio_list, &node->prio_list);
+		}
+		list_del_init(&node->prio_list);
+	}
+
+	list_del_init(&node->node_list);
+
+	plist_check_head(head);
+}
+
+/**
+ * plist_requeue - Requeue @node at end of same-prio entries.
+ *
+ * This is essentially an optimized plist_del() followed by
+ * plist_add().  It moves an entry already in the plist to
+ * after any other same-priority entries.
+ *
+ * @node:	&struct plist_node pointer - entry to be moved
+ * @head:	&struct plist_head pointer - list head
+ */
+void plist_requeue(struct plist_node *node, struct plist_head *head)
+{
+	struct plist_node *iter;
+	struct list_head *node_next = &head->node_list;
+
+	plist_check_head(head);
+	BUG_ON(plist_head_empty(head));
+	BUG_ON(plist_node_empty(node));
+
+	if (node == plist_last(head))
+		return;
+
+	iter = plist_next(node);
+
+	if (node->prio != iter->prio)
+		return;
+
+	plist_del(node, head);
+
+	/*
+	 * After plist_del(), iter is the replacement of the node.  If the node
+	 * was on prio_list, take shortcut to find node_next instead of looping.
+	 */
+	if (!list_empty(&iter->prio_list)) {
+		iter = list_entry(iter->prio_list.next, struct plist_node,
+				  prio_list);
+		node_next = &iter->node_list;
+		goto queue;
+	}
+
+	plist_for_each_continue(iter, head) {
+		if (node->prio != iter->prio) {
+			node_next = &iter->node_list;
+			break;
+		}
+	}
+queue:
+	list_add_tail(&node->node_list, node_next);
+
+	plist_check_head(head);
+}
+
+#ifdef CONFIG_DEBUG_PLIST
+#include <linux/sched.h>
+#include <linux/sched/clock.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+static struct plist_node __initdata test_node[241];
+
+static void __init plist_test_check(int nr_expect)
+{
+	struct plist_node *first, *prio_pos, *node_pos;
+
+	if (plist_head_empty(&test_head)) {
+		BUG_ON(nr_expect != 0);
+		return;
+	}
+
+	prio_pos = first = plist_first(&test_head);
+	plist_for_each(node_pos, &test_head) {
+		if (nr_expect-- < 0)
+			break;
+		if (node_pos == first)
+			continue;
+		if (node_pos->prio == prio_pos->prio) {
+			BUG_ON(!list_empty(&node_pos->prio_list));
+			continue;
+		}
+
+		BUG_ON(prio_pos->prio > node_pos->prio);
+		BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
+		prio_pos = node_pos;
+	}
+
+	BUG_ON(nr_expect != 0);
+	BUG_ON(prio_pos->prio_list.next != &first->prio_list);
+}
+
+static void __init plist_test_requeue(struct plist_node *node)
+{
+	plist_requeue(node, &test_head);
+
+	if (node != plist_last(&test_head))
+		BUG_ON(node->prio == plist_next(node)->prio);
+}
+
+static int  __init plist_test(void)
+{
+	int nr_expect = 0, i, loop;
+	unsigned int r = local_clock();
+
+	printk(KERN_DEBUG "start plist test\n");
+	plist_head_init(&test_head);
+	for (i = 0; i < ARRAY_SIZE(test_node); i++)
+		plist_node_init(test_node + i, 0);
+
+	for (loop = 0; loop < 1000; loop++) {
+		r = r * 193939 % 47629;
+		i = r % ARRAY_SIZE(test_node);
+		if (plist_node_empty(test_node + i)) {
+			r = r * 193939 % 47629;
+			test_node[i].prio = r % 99;
+			plist_add(test_node + i, &test_head);
+			nr_expect++;
+		} else {
+			plist_del(test_node + i, &test_head);
+			nr_expect--;
+		}
+		plist_test_check(nr_expect);
+		if (!plist_node_empty(test_node + i)) {
+			plist_test_requeue(test_node + i);
+			plist_test_check(nr_expect);
+		}
+	}
+
+	for (i = 0; i < ARRAY_SIZE(test_node); i++) {
+		if (plist_node_empty(test_node + i))
+			continue;
+		plist_del(test_node + i, &test_head);
+		nr_expect--;
+		plist_test_check(nr_expect);
+	}
+
+	printk(KERN_DEBUG "end plist test\n");
+
+	/* Worst case test for plist_add() */
+	unsigned int test_data[241];
+
+	for (i = 0; i < ARRAY_SIZE(test_data); i++)
+		test_data[i] = i;
+
+	ktime_t start, end, time_elapsed = 0;
+
+	plist_head_init(&test_head);
+
+	for (i = 0; i < ARRAY_SIZE(test_node); i++) {
+		plist_node_init(test_node + i, 0);
+		test_node[i].prio = test_data[i];
+	}
+
+	for (i = 0; i < ARRAY_SIZE(test_node); i++) {
+		if (plist_node_empty(test_node + i)) {
+			start = ktime_get();
+			plist_add(test_node + i, &test_head);
+			end = ktime_get();
+			time_elapsed += (end - start);
+		}
+	}
+
+	pr_debug("plist_add worst case test time elapsed %lld\n", time_elapsed);
+	return 0;
+}
+
+module_init(plist_test);
+
+#endif