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, 178 insertions, 0 deletions

diff --git a/lib/kunit/resource.c b/lib/kunit/resource.c
new file mode 100644
index 000000000..45e55238c
--- /dev/null
+++ b/lib/kunit/resource.c
@@ -0,0 +1,178 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit resource API for test managed resources (allocations, etc.).
+ *
+ * Copyright (C) 2022, Google LLC.
+ * Author: Daniel Latypov <dlatypov@google.com>
+ */
+
+#include <kunit/resource.h>
+#include <kunit/test.h>
+#include <linux/kref.h>
+
+/*
+ * Used for static resources and when a kunit_resource * has been created by
+ * kunit_alloc_resource().  When an init function is supplied, @data is passed
+ * into the init function; otherwise, we simply set the resource data field to
+ * the data value passed in. Doesn't initialize res->should_kfree.
+ */
+int __kunit_add_resource(struct kunit *test,
+			 kunit_resource_init_t init,
+			 kunit_resource_free_t free,
+			 struct kunit_resource *res,
+			 void *data)
+{
+	int ret = 0;
+	unsigned long flags;
+
+	res->free = free;
+	kref_init(&res->refcount);
+
+	if (init) {
+		ret = init(res, data);
+		if (ret)
+			return ret;
+	} else {
+		res->data = data;
+	}
+
+	spin_lock_irqsave(&test->lock, flags);
+	list_add_tail(&res->node, &test->resources);
+	/* refcount for list is established by kref_init() */
+	spin_unlock_irqrestore(&test->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__kunit_add_resource);
+
+void kunit_remove_resource(struct kunit *test, struct kunit_resource *res)
+{
+	unsigned long flags;
+	bool was_linked;
+
+	spin_lock_irqsave(&test->lock, flags);
+	was_linked = !list_empty(&res->node);
+	list_del_init(&res->node);
+	spin_unlock_irqrestore(&test->lock, flags);
+
+	if (was_linked)
+		kunit_put_resource(res);
+}
+EXPORT_SYMBOL_GPL(kunit_remove_resource);
+
+int kunit_destroy_resource(struct kunit *test, kunit_resource_match_t match,
+			   void *match_data)
+{
+	struct kunit_resource *res = kunit_find_resource(test, match,
+							 match_data);
+
+	if (!res)
+		return -ENOENT;
+
+	kunit_remove_resource(test, res);
+
+	/* We have a reference also via _find(); drop it. */
+	kunit_put_resource(res);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kunit_destroy_resource);
+
+struct kunit_action_ctx {
+	struct kunit_resource res;
+	kunit_action_t *func;
+	void *ctx;
+};
+
+static void __kunit_action_free(struct kunit_resource *res)
+{
+	struct kunit_action_ctx *action_ctx = container_of(res, struct kunit_action_ctx, res);
+
+	action_ctx->func(action_ctx->ctx);
+}
+
+
+int kunit_add_action(struct kunit *test, void (*action)(void *), void *ctx)
+{
+	struct kunit_action_ctx *action_ctx;
+
+	KUNIT_ASSERT_NOT_NULL_MSG(test, action, "Tried to action a NULL function!");
+
+	action_ctx = kzalloc_obj(*action_ctx);
+	if (!action_ctx)
+		return -ENOMEM;
+
+	action_ctx->func = action;
+	action_ctx->ctx = ctx;
+
+	action_ctx->res.should_kfree = true;
+	/* As init is NULL, this cannot fail. */
+	__kunit_add_resource(test, NULL, __kunit_action_free, &action_ctx->res, action_ctx);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kunit_add_action);
+
+int kunit_add_action_or_reset(struct kunit *test, void (*action)(void *),
+			      void *ctx)
+{
+	int res = kunit_add_action(test, action, ctx);
+
+	if (res)
+		action(ctx);
+	return res;
+}
+EXPORT_SYMBOL_GPL(kunit_add_action_or_reset);
+
+static bool __kunit_action_match(struct kunit *test,
+				struct kunit_resource *res, void *match_data)
+{
+	struct kunit_action_ctx *match_ctx = (struct kunit_action_ctx *)match_data;
+	struct kunit_action_ctx *res_ctx = container_of(res, struct kunit_action_ctx, res);
+
+	/* Make sure this is a free function. */
+	if (res->free != __kunit_action_free)
+		return false;
+
+	/* Both the function and context data should match. */
+	return (match_ctx->func == res_ctx->func) && (match_ctx->ctx == res_ctx->ctx);
+}
+
+void kunit_remove_action(struct kunit *test,
+			kunit_action_t *action,
+			void *ctx)
+{
+	struct kunit_action_ctx match_ctx;
+	struct kunit_resource *res;
+
+	match_ctx.func = action;
+	match_ctx.ctx = ctx;
+
+	res = kunit_find_resource(test, __kunit_action_match, &match_ctx);
+	if (res) {
+		/* Remove the free function so we don't run the action. */
+		res->free = NULL;
+		kunit_remove_resource(test, res);
+		kunit_put_resource(res);
+	}
+}
+EXPORT_SYMBOL_GPL(kunit_remove_action);
+
+void kunit_release_action(struct kunit *test,
+			 kunit_action_t *action,
+			 void *ctx)
+{
+	struct kunit_action_ctx match_ctx;
+	struct kunit_resource *res;
+
+	match_ctx.func = action;
+	match_ctx.ctx = ctx;
+
+	res = kunit_find_resource(test, __kunit_action_match, &match_ctx);
+	if (res) {
+		kunit_remove_resource(test, res);
+		/* We have to put() this here, else free won't be called. */
+		kunit_put_resource(res);
+	}
+}
+EXPORT_SYMBOL_GPL(kunit_release_action);