openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 114 insertions, 0 deletions

diff --git a/drivers/input/misc/gpio-beeper.c b/drivers/input/misc/gpio-beeper.c
new file mode 100644
index 000000000..3d65cb4f4
--- /dev/null
+++ b/drivers/input/misc/gpio-beeper.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic GPIO beeper driver
+ *
+ * Copyright (C) 2013-2014 Alexander Shiyan <shc_work@mail.ru>
+ */
+
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/gpio/consumer.h>
+#include <linux/of.h>
+#include <linux/workqueue.h>
+#include <linux/platform_device.h>
+
+#define BEEPER_MODNAME		"gpio-beeper"
+
+struct gpio_beeper {
+	struct work_struct	work;
+	struct gpio_desc	*desc;
+	bool			beeping;
+};
+
+static void gpio_beeper_toggle(struct gpio_beeper *beep, bool on)
+{
+	gpiod_set_value_cansleep(beep->desc, on);
+}
+
+static void gpio_beeper_work(struct work_struct *work)
+{
+	struct gpio_beeper *beep = container_of(work, struct gpio_beeper, work);
+
+	gpio_beeper_toggle(beep, beep->beeping);
+}
+
+static int gpio_beeper_event(struct input_dev *dev, unsigned int type,
+			     unsigned int code, int value)
+{
+	struct gpio_beeper *beep = input_get_drvdata(dev);
+
+	if (type != EV_SND || code != SND_BELL)
+		return -ENOTSUPP;
+
+	if (value < 0)
+		return -EINVAL;
+
+	beep->beeping = value;
+	/* Schedule work to actually turn the beeper on or off */
+	schedule_work(&beep->work);
+
+	return 0;
+}
+
+static void gpio_beeper_close(struct input_dev *input)
+{
+	struct gpio_beeper *beep = input_get_drvdata(input);
+
+	cancel_work_sync(&beep->work);
+	gpio_beeper_toggle(beep, false);
+}
+
+static int gpio_beeper_probe(struct platform_device *pdev)
+{
+	struct gpio_beeper *beep;
+	struct input_dev *input;
+
+	beep = devm_kzalloc(&pdev->dev, sizeof(*beep), GFP_KERNEL);
+	if (!beep)
+		return -ENOMEM;
+
+	beep->desc = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
+	if (IS_ERR(beep->desc))
+		return PTR_ERR(beep->desc);
+
+	input = devm_input_allocate_device(&pdev->dev);
+	if (!input)
+		return -ENOMEM;
+
+	INIT_WORK(&beep->work, gpio_beeper_work);
+
+	input->name		= pdev->name;
+	input->id.bustype	= BUS_HOST;
+	input->id.vendor	= 0x0001;
+	input->id.product	= 0x0001;
+	input->id.version	= 0x0100;
+	input->close		= gpio_beeper_close;
+	input->event		= gpio_beeper_event;
+
+	input_set_capability(input, EV_SND, SND_BELL);
+
+	input_set_drvdata(input, beep);
+
+	return input_register_device(input);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id gpio_beeper_of_match[] = {
+	{ .compatible = "gpio-beeper", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, gpio_beeper_of_match);
+#endif
+
+static struct platform_driver gpio_beeper_platform_driver = {
+	.driver	= {
+		.name		= BEEPER_MODNAME,
+		.of_match_table	= of_match_ptr(gpio_beeper_of_match),
+	},
+	.probe	= gpio_beeper_probe,
+};
+module_platform_driver(gpio_beeper_platform_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
+MODULE_DESCRIPTION("Generic GPIO beeper driver");