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, 122 insertions, 0 deletions

diff --git a/drivers/usb/serial/empeg.c b/drivers/usb/serial/empeg.c
new file mode 100644
index 000000000..4937575ca
--- /dev/null
+++ b/drivers/usb/serial/empeg.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB Empeg empeg-car player driver
+ *
+ *	Copyright (C) 2000, 2001
+ *	    Gary Brubaker (xavyer@ix.netcom.com)
+ *
+ *	Copyright (C) 1999 - 2001
+ *	    Greg Kroah-Hartman (greg@kroah.com)
+ *
+ * See Documentation/usb/usb-serial.rst for more information on using this
+ * driver
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+#define DRIVER_AUTHOR "Greg Kroah-Hartman <greg@kroah.com>, Gary Brubaker <xavyer@ix.netcom.com>"
+#define DRIVER_DESC "USB Empeg Mark I/II Driver"
+
+#define EMPEG_VENDOR_ID			0x084f
+#define EMPEG_PRODUCT_ID		0x0001
+
+/* function prototypes for an empeg-car player */
+static int  empeg_startup(struct usb_serial *serial);
+static void empeg_init_termios(struct tty_struct *tty);
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(EMPEG_VENDOR_ID, EMPEG_PRODUCT_ID) },
+	{ }					/* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE(usb, id_table);
+
+static struct usb_serial_driver empeg_device = {
+	.driver = {
+		.name =		"empeg",
+	},
+	.id_table =		id_table,
+	.num_ports =		1,
+	.bulk_out_size =	256,
+	.throttle =		usb_serial_generic_throttle,
+	.unthrottle =		usb_serial_generic_unthrottle,
+	.attach =		empeg_startup,
+	.init_termios =		empeg_init_termios,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&empeg_device, NULL
+};
+
+static int empeg_startup(struct usb_serial *serial)
+{
+	int r;
+
+	if (serial->dev->actconfig->desc.bConfigurationValue != 1) {
+		dev_err(&serial->dev->dev, "active config #%d != 1 ??\n",
+			serial->dev->actconfig->desc.bConfigurationValue);
+		return -ENODEV;
+	}
+
+	r = usb_reset_configuration(serial->dev);
+
+	/* continue on with initialization */
+	return r;
+}
+
+static void empeg_init_termios(struct tty_struct *tty)
+{
+	struct ktermios *termios = &tty->termios;
+
+	/*
+	 * The empeg-car player wants these particular tty settings.
+	 * You could, for example, change the baud rate, however the
+	 * player only supports 115200 (currently), so there is really
+	 * no point in support for changes to the tty settings.
+	 * (at least for now)
+	 *
+	 * The default requirements for this device are:
+	 */
+	termios->c_iflag
+		&= ~(IGNBRK	/* disable ignore break */
+		| BRKINT	/* disable break causes interrupt */
+		| PARMRK	/* disable mark parity errors */
+		| ISTRIP	/* disable clear high bit of input characters */
+		| INLCR		/* disable translate NL to CR */
+		| IGNCR		/* disable ignore CR */
+		| ICRNL		/* disable translate CR to NL */
+		| IXON);	/* disable enable XON/XOFF flow control */
+
+	termios->c_oflag
+		&= ~OPOST;	/* disable postprocess output characters */
+
+	termios->c_lflag
+		&= ~(ECHO	/* disable echo input characters */
+		| ECHONL	/* disable echo new line */
+		| ICANON	/* disable erase, kill, werase, and rprnt special characters */
+		| ISIG		/* disable interrupt, quit, and suspend special characters */
+		| IEXTEN);	/* disable non-POSIX special characters */
+
+	termios->c_cflag
+		&= ~(CSIZE	/* no size */
+		| PARENB	/* disable parity bit */
+		| CBAUD);	/* clear current baud rate */
+
+	termios->c_cflag
+		|= CS8;		/* character size 8 bits */
+
+	tty_encode_baud_rate(tty, 115200, 115200);
+}
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL v2");