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, 207 insertions, 0 deletions

diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c
new file mode 100644
index 000000000..6f88b507f
--- /dev/null
+++ b/security/keys/user_defined.c
@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* user_defined.c: user defined key type
+ *
+ * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/export.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/seq_file.h>
+#include <linux/err.h>
+#include <keys/user-type.h>
+#include <linux/uaccess.h>
+#include "internal.h"
+
+static int logon_vet_description(const char *desc);
+
+/*
+ * user defined keys take an arbitrary string as the description and an
+ * arbitrary blob of data as the payload
+ */
+struct key_type key_type_user = {
+	.name			= "user",
+	.preparse		= user_preparse,
+	.free_preparse		= user_free_preparse,
+	.instantiate		= generic_key_instantiate,
+	.update			= user_update,
+	.revoke			= user_revoke,
+	.destroy		= user_destroy,
+	.describe		= user_describe,
+	.read			= user_read,
+};
+
+EXPORT_SYMBOL_GPL(key_type_user);
+
+/*
+ * This key type is essentially the same as key_type_user, but it does
+ * not define a .read op. This is suitable for storing username and
+ * password pairs in the keyring that you do not want to be readable
+ * from userspace.
+ */
+struct key_type key_type_logon = {
+	.name			= "logon",
+	.preparse		= user_preparse,
+	.free_preparse		= user_free_preparse,
+	.instantiate		= generic_key_instantiate,
+	.update			= user_update,
+	.revoke			= user_revoke,
+	.destroy		= user_destroy,
+	.describe		= user_describe,
+	.vet_description	= logon_vet_description,
+};
+EXPORT_SYMBOL_GPL(key_type_logon);
+
+/*
+ * Preparse a user defined key payload
+ */
+int user_preparse(struct key_preparsed_payload *prep)
+{
+	struct user_key_payload *upayload;
+	size_t datalen = prep->datalen;
+
+	if (datalen == 0 || datalen > 32767 || !prep->data)
+		return -EINVAL;
+
+	upayload = kmalloc_flex(*upayload, data, datalen);
+	if (!upayload)
+		return -ENOMEM;
+
+	/* attach the data */
+	prep->quotalen = datalen;
+	prep->payload.data[0] = upayload;
+	upayload->datalen = datalen;
+	memcpy(upayload->data, prep->data, datalen);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(user_preparse);
+
+/*
+ * Free a preparse of a user defined key payload
+ */
+void user_free_preparse(struct key_preparsed_payload *prep)
+{
+	kfree_sensitive(prep->payload.data[0]);
+}
+EXPORT_SYMBOL_GPL(user_free_preparse);
+
+static void user_free_payload_rcu(struct rcu_head *head)
+{
+	struct user_key_payload *payload;
+
+	payload = container_of(head, struct user_key_payload, rcu);
+	kfree_sensitive(payload);
+}
+
+/*
+ * update a user defined key
+ * - the key's semaphore is write-locked
+ */
+int user_update(struct key *key, struct key_preparsed_payload *prep)
+{
+	struct user_key_payload *zap = NULL;
+	int ret;
+
+	/* check the quota and attach the new data */
+	ret = key_payload_reserve(key, prep->datalen);
+	if (ret < 0)
+		return ret;
+
+	/* attach the new data, displacing the old */
+	key->expiry = prep->expiry;
+	if (key_is_positive(key))
+		zap = dereference_key_locked(key);
+	rcu_assign_keypointer(key, prep->payload.data[0]);
+	prep->payload.data[0] = NULL;
+
+	if (zap)
+		call_rcu(&zap->rcu, user_free_payload_rcu);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(user_update);
+
+/*
+ * dispose of the links from a revoked keyring
+ * - called with the key sem write-locked
+ */
+void user_revoke(struct key *key)
+{
+	struct user_key_payload *upayload = user_key_payload_locked(key);
+
+	/* clear the quota */
+	key_payload_reserve(key, 0);
+
+	if (upayload) {
+		rcu_assign_keypointer(key, NULL);
+		call_rcu(&upayload->rcu, user_free_payload_rcu);
+	}
+}
+
+EXPORT_SYMBOL(user_revoke);
+
+/*
+ * dispose of the data dangling from the corpse of a user key
+ */
+void user_destroy(struct key *key)
+{
+	struct user_key_payload *upayload = key->payload.data[0];
+
+	kfree_sensitive(upayload);
+}
+
+EXPORT_SYMBOL_GPL(user_destroy);
+
+/*
+ * describe the user key
+ */
+void user_describe(const struct key *key, struct seq_file *m)
+{
+	seq_puts(m, key->description);
+	if (key_is_positive(key))
+		seq_printf(m, ": %u", key->datalen);
+}
+
+EXPORT_SYMBOL_GPL(user_describe);
+
+/*
+ * read the key data
+ * - the key's semaphore is read-locked
+ */
+long user_read(const struct key *key, char *buffer, size_t buflen)
+{
+	const struct user_key_payload *upayload;
+	long ret;
+
+	upayload = user_key_payload_locked(key);
+	ret = upayload->datalen;
+
+	/* we can return the data as is */
+	if (buffer && buflen > 0) {
+		if (buflen > upayload->datalen)
+			buflen = upayload->datalen;
+
+		memcpy(buffer, upayload->data, buflen);
+	}
+
+	return ret;
+}
+
+EXPORT_SYMBOL_GPL(user_read);
+
+/* Vet the description for a "logon" key */
+static int logon_vet_description(const char *desc)
+{
+	char *p;
+
+	/* require a "qualified" description string */
+	p = strchr(desc, ':');
+	if (!p)
+		return -EINVAL;
+
+	/* also reject description with ':' as first char */
+	if (p == desc)
+		return -EINVAL;
+
+	return 0;
+}