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, 153 insertions, 0 deletions

diff --git a/drivers/input/keyboard/stowaway.c b/drivers/input/keyboard/stowaway.c
new file mode 100644
index 000000000..eade05542
--- /dev/null
+++ b/drivers/input/keyboard/stowaway.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Stowaway keyboard driver for Linux
+ */
+
+/*
+ *  Copyright (c) 2006 Marek Vasut
+ *
+ *  Based on Newton keyboard driver for Linux
+ *  by Justin Cormack
+ */
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"Stowaway keyboard driver"
+
+MODULE_AUTHOR("Marek Vasut <marek.vasut@gmail.com>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+#define SKBD_KEY_MASK	0x7f
+#define SKBD_RELEASE	0x80
+
+static unsigned char skbd_keycode[128] = {
+	KEY_1, KEY_2, KEY_3, KEY_Z, KEY_4, KEY_5, KEY_6, KEY_7,
+	0, KEY_Q, KEY_W, KEY_E, KEY_R, KEY_T, KEY_Y, KEY_GRAVE,
+	KEY_X, KEY_A, KEY_S, KEY_D, KEY_F, KEY_G, KEY_H, KEY_SPACE,
+	KEY_CAPSLOCK, KEY_TAB, KEY_LEFTCTRL, 0, 0, 0, 0, 0,
+	0, 0, 0, KEY_LEFTALT, 0, 0, 0, 0,
+	0, 0, 0, 0, KEY_C, KEY_V, KEY_B, KEY_N,
+	KEY_MINUS, KEY_EQUAL, KEY_BACKSPACE, KEY_HOME, KEY_8, KEY_9, KEY_0, KEY_ESC,
+	KEY_LEFTBRACE, KEY_RIGHTBRACE, KEY_BACKSLASH, KEY_END, KEY_U, KEY_I, KEY_O, KEY_P,
+	KEY_APOSTROPHE, KEY_ENTER, KEY_PAGEUP,0, KEY_J, KEY_K, KEY_L, KEY_SEMICOLON,
+	KEY_SLASH, KEY_UP, KEY_PAGEDOWN, 0,KEY_M, KEY_COMMA, KEY_DOT, KEY_INSERT,
+	KEY_DELETE, KEY_LEFT, KEY_DOWN, KEY_RIGHT,  0, 0, 0,
+	KEY_LEFTSHIFT, KEY_RIGHTSHIFT, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, KEY_F1, KEY_F2, KEY_F3, KEY_F4, KEY_F5, KEY_F6, KEY_F7,
+	KEY_F8, KEY_F9, KEY_F10, KEY_F11, KEY_F12, 0, 0, 0
+};
+
+struct skbd {
+	unsigned char keycode[128];
+	struct input_dev *dev;
+	struct serio *serio;
+	char phys[32];
+};
+
+static irqreturn_t skbd_interrupt(struct serio *serio, unsigned char data,
+				  unsigned int flags)
+{
+	struct skbd *skbd = serio_get_drvdata(serio);
+	struct input_dev *dev = skbd->dev;
+
+	if (skbd->keycode[data & SKBD_KEY_MASK]) {
+		input_report_key(dev, skbd->keycode[data & SKBD_KEY_MASK],
+				 !(data & SKBD_RELEASE));
+		input_sync(dev);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int skbd_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct skbd *skbd;
+	struct input_dev *input_dev;
+	int err = -ENOMEM;
+	int i;
+
+	skbd = kzalloc_obj(*skbd);
+	input_dev = input_allocate_device();
+	if (!skbd || !input_dev)
+		goto fail1;
+
+	skbd->serio = serio;
+	skbd->dev = input_dev;
+	snprintf(skbd->phys, sizeof(skbd->phys), "%s/input0", serio->phys);
+	memcpy(skbd->keycode, skbd_keycode, sizeof(skbd->keycode));
+
+	input_dev->name = "Stowaway Keyboard";
+	input_dev->phys = skbd->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_STOWAWAY;
+	input_dev->id.product = 0x0001;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
+	input_dev->keycode = skbd->keycode;
+	input_dev->keycodesize = sizeof(unsigned char);
+	input_dev->keycodemax = ARRAY_SIZE(skbd_keycode);
+	for (i = 0; i < ARRAY_SIZE(skbd_keycode); i++)
+		set_bit(skbd_keycode[i], input_dev->keybit);
+	clear_bit(0, input_dev->keybit);
+
+	serio_set_drvdata(serio, skbd);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(skbd->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3: serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(skbd);
+	return err;
+}
+
+static void skbd_disconnect(struct serio *serio)
+{
+	struct skbd *skbd = serio_get_drvdata(serio);
+
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_unregister_device(skbd->dev);
+	kfree(skbd);
+}
+
+static const struct serio_device_id skbd_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_STOWAWAY,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, skbd_serio_ids);
+
+static struct serio_driver skbd_drv = {
+	.driver		= {
+		.name	= "stowaway",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= skbd_serio_ids,
+	.interrupt	= skbd_interrupt,
+	.connect	= skbd_connect,
+	.disconnect	= skbd_disconnect,
+};
+
+module_serio_driver(skbd_drv);