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, 94 insertions, 0 deletions

diff --git a/drivers/input/misc/rave-sp-pwrbutton.c b/drivers/input/misc/rave-sp-pwrbutton.c
new file mode 100644
index 000000000..bcab3cdb7
--- /dev/null
+++ b/drivers/input/misc/rave-sp-pwrbutton.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Power Button driver for RAVE SP
+//
+// Copyright (C) 2017 Zodiac Inflight Innovations
+//
+//
+
+#include <linux/input.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/rave-sp.h>
+#include <linux/platform_device.h>
+
+#define RAVE_SP_EVNT_BUTTON_PRESS	(RAVE_SP_EVNT_BASE + 0x00)
+
+struct rave_sp_power_button {
+	struct input_dev *idev;
+	struct notifier_block nb;
+};
+
+static int rave_sp_power_button_event(struct notifier_block *nb,
+				      unsigned long action, void *data)
+{
+	struct rave_sp_power_button *pb =
+		container_of(nb, struct rave_sp_power_button, nb);
+	const u8 event = rave_sp_action_unpack_event(action);
+	const u8 value = rave_sp_action_unpack_value(action);
+	struct input_dev *idev = pb->idev;
+
+	if (event == RAVE_SP_EVNT_BUTTON_PRESS) {
+		input_report_key(idev, KEY_POWER, value);
+		input_sync(idev);
+
+		return NOTIFY_STOP;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static int rave_sp_pwrbutton_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct rave_sp_power_button *pb;
+	struct input_dev *idev;
+	int error;
+
+	pb = devm_kzalloc(dev, sizeof(*pb), GFP_KERNEL);
+	if (!pb)
+		return -ENOMEM;
+
+	idev = devm_input_allocate_device(dev);
+	if (!idev)
+		return -ENOMEM;
+
+	idev->name = pdev->name;
+
+	input_set_capability(idev, EV_KEY, KEY_POWER);
+
+	error = input_register_device(idev);
+	if (error)
+		return error;
+
+	pb->idev = idev;
+	pb->nb.notifier_call = rave_sp_power_button_event;
+	pb->nb.priority = 128;
+
+	error = devm_rave_sp_register_event_notifier(dev, &pb->nb);
+	if (error)
+		return error;
+
+	return 0;
+}
+
+static const struct of_device_id rave_sp_pwrbutton_of_match[] = {
+	{ .compatible = "zii,rave-sp-pwrbutton" },
+	{}
+};
+
+static struct platform_driver rave_sp_pwrbutton_driver = {
+	.probe = rave_sp_pwrbutton_probe,
+	.driver	= {
+		.name = KBUILD_MODNAME,
+		.of_match_table = rave_sp_pwrbutton_of_match,
+	},
+};
+module_platform_driver(rave_sp_pwrbutton_driver);
+
+MODULE_DEVICE_TABLE(of, rave_sp_pwrbutton_of_match);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Andrey Vostrikov <andrey.vostrikov@cogentembedded.com>");
+MODULE_AUTHOR("Nikita Yushchenko <nikita.yoush@cogentembedded.com>");
+MODULE_AUTHOR("Andrey Smirnov <andrew.smirnov@gmail.com>");
+MODULE_DESCRIPTION("RAVE SP Power Button driver");