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, 106 insertions, 0 deletions

diff --git a/drivers/hid/hid-viewsonic.c b/drivers/hid/hid-viewsonic.c
new file mode 100644
index 000000000..532bed88b
--- /dev/null
+++ b/drivers/hid/hid-viewsonic.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  HID driver for ViewSonic devices not fully compliant with HID standard
+ *
+ *  Copyright (c) 2017 Nikolai Kondrashov
+ */
+
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+/* Size of the original descriptor of PD1011 signature pad */
+#define PD1011_RDESC_ORIG_SIZE	408
+
+/* Fixed report descriptor of PD1011 signature pad */
+static const __u8 pd1011_rdesc_fixed[] = {
+	0x05, 0x0D,             /*  Usage Page (Digitizer),             */
+	0x09, 0x01,             /*  Usage (Digitizer),                  */
+	0xA1, 0x01,             /*  Collection (Application),           */
+	0x85, 0x02,             /*      Report ID (2),                  */
+	0x09, 0x20,             /*      Usage (Stylus),                 */
+	0xA0,                   /*      Collection (Physical),          */
+	0x75, 0x10,             /*          Report Size (16),           */
+	0x95, 0x01,             /*          Report Count (1),           */
+	0xA4,                   /*          Push,                       */
+	0x05, 0x01,             /*          Usage Page (Desktop),       */
+	0x65, 0x13,             /*          Unit (Inch),                */
+	0x55, 0xFD,             /*          Unit Exponent (-3),         */
+	0x34,                   /*          Physical Minimum (0),       */
+	0x09, 0x30,             /*          Usage (X),                  */
+	0x46, 0x5D, 0x21,       /*          Physical Maximum (8541),    */
+	0x27, 0x80, 0xA9,
+		0x00, 0x00,     /*          Logical Maximum (43392),    */
+	0x81, 0x02,             /*          Input (Variable),           */
+	0x09, 0x31,             /*          Usage (Y),                  */
+	0x46, 0xDA, 0x14,       /*          Physical Maximum (5338),    */
+	0x26, 0xF0, 0x69,       /*          Logical Maximum (27120),    */
+	0x81, 0x02,             /*          Input (Variable),           */
+	0xB4,                   /*          Pop,                        */
+	0x14,                   /*          Logical Minimum (0),        */
+	0x25, 0x01,             /*          Logical Maximum (1),        */
+	0x75, 0x01,             /*          Report Size (1),            */
+	0x95, 0x01,             /*          Report Count (1),           */
+	0x81, 0x03,             /*          Input (Constant, Variable), */
+	0x09, 0x32,             /*          Usage (In Range),           */
+	0x09, 0x42,             /*          Usage (Tip Switch),         */
+	0x95, 0x02,             /*          Report Count (2),           */
+	0x81, 0x02,             /*          Input (Variable),           */
+	0x95, 0x05,             /*          Report Count (5),           */
+	0x81, 0x03,             /*          Input (Constant, Variable), */
+	0x75, 0x10,             /*          Report Size (16),           */
+	0x95, 0x01,             /*          Report Count (1),           */
+	0x09, 0x30,             /*          Usage (Tip Pressure),       */
+	0x15, 0x05,             /*          Logical Minimum (5),        */
+	0x26, 0xFF, 0x07,       /*          Logical Maximum (2047),     */
+	0x81, 0x02,             /*          Input (Variable),           */
+	0x75, 0x10,             /*          Report Size (16),           */
+	0x95, 0x01,             /*          Report Count (1),           */
+	0x81, 0x03,             /*          Input (Constant, Variable), */
+	0xC0,                   /*      End Collection,                 */
+	0xC0                    /*  End Collection                      */
+};
+
+static const __u8 *viewsonic_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+					  unsigned int *rsize)
+{
+	switch (hdev->product) {
+	case USB_DEVICE_ID_VIEWSONIC_PD1011:
+	case USB_DEVICE_ID_SIGNOTEC_VIEWSONIC_PD1011:
+		if (*rsize == PD1011_RDESC_ORIG_SIZE) {
+			*rsize = sizeof(pd1011_rdesc_fixed);
+			return pd1011_rdesc_fixed;
+		}
+		break;
+	}
+
+	return rdesc;
+}
+
+static const struct hid_device_id viewsonic_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_VIEWSONIC,
+				USB_DEVICE_ID_VIEWSONIC_PD1011) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_SIGNOTEC,
+				USB_DEVICE_ID_SIGNOTEC_VIEWSONIC_PD1011) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, viewsonic_devices);
+
+static struct hid_driver viewsonic_driver = {
+	.name = "viewsonic",
+	.id_table = viewsonic_devices,
+	.report_fixup = viewsonic_report_fixup,
+};
+module_hid_driver(viewsonic_driver);
+
+MODULE_DESCRIPTION("HID driver for ViewSonic devices not fully compliant with HID standard");
+MODULE_LICENSE("GPL");