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, 143 insertions, 0 deletions

diff --git a/drivers/misc/hmc6352.c b/drivers/misc/hmc6352.c
new file mode 100644
index 000000000..ff92c6edf
--- /dev/null
+++ b/drivers/misc/hmc6352.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * hmc6352.c - Honeywell Compass Driver
+ *
+ * Copyright (C) 2009 Intel Corp
+ *
+ *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/sysfs.h>
+#include <linux/nospec.h>
+
+static DEFINE_MUTEX(compass_mutex);
+
+static int compass_command(struct i2c_client *c, u8 cmd)
+{
+	int ret = i2c_master_send(c, &cmd, 1);
+	if (ret < 0)
+		dev_warn(&c->dev, "command '%c' failed.\n", cmd);
+	return ret;
+}
+
+static int compass_store(struct device *dev, const char *buf, size_t count,
+			const char *map)
+{
+	struct i2c_client *c = to_i2c_client(dev);
+	int ret;
+	unsigned long val;
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret)
+		return ret;
+	if (val >= strlen(map))
+		return -EINVAL;
+	val = array_index_nospec(val, strlen(map));
+	mutex_lock(&compass_mutex);
+	ret = compass_command(c, map[val]);
+	mutex_unlock(&compass_mutex);
+	if (ret < 0)
+		return ret;
+	return count;
+}
+
+static ssize_t compass_calibration_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	return compass_store(dev, buf, count, "EC");
+}
+
+static ssize_t compass_power_mode_store(struct device *dev,
+		struct device_attribute *attr, const  char *buf, size_t count)
+{
+	return compass_store(dev, buf, count, "SW");
+}
+
+static ssize_t compass_heading_data_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	unsigned char i2c_data[2];
+	int ret;
+
+	mutex_lock(&compass_mutex);
+	ret = compass_command(client, 'A');
+	if (ret != 1) {
+		mutex_unlock(&compass_mutex);
+		return ret;
+	}
+	msleep(10); /* sending 'A' cmd we need to wait for 7-10 millisecs */
+	ret = i2c_master_recv(client, i2c_data, 2);
+	mutex_unlock(&compass_mutex);
+	if (ret < 0) {
+		dev_warn(dev, "i2c read data cmd failed\n");
+		return ret;
+	}
+	ret = (i2c_data[0] << 8) | i2c_data[1];
+	return sprintf(buf, "%d.%d\n", ret/10, ret%10);
+}
+
+
+static DEVICE_ATTR(heading0_input, S_IRUGO, compass_heading_data_show, NULL);
+static DEVICE_ATTR(calibration, S_IWUSR, NULL, compass_calibration_store);
+static DEVICE_ATTR(power_state, S_IWUSR, NULL, compass_power_mode_store);
+
+static struct attribute *mid_att_compass[] = {
+	&dev_attr_heading0_input.attr,
+	&dev_attr_calibration.attr,
+	&dev_attr_power_state.attr,
+	NULL
+};
+
+static const struct attribute_group m_compass_gr = {
+	.name = "hmc6352",
+	.attrs = mid_att_compass
+};
+
+static int hmc6352_probe(struct i2c_client *client)
+{
+	int res;
+
+	res = sysfs_create_group(&client->dev.kobj, &m_compass_gr);
+	if (res) {
+		dev_err(&client->dev, "device_create_file failed\n");
+		return res;
+	}
+	dev_info(&client->dev, "%s HMC6352 compass chip found\n",
+							client->name);
+	return 0;
+}
+
+static void hmc6352_remove(struct i2c_client *client)
+{
+	sysfs_remove_group(&client->dev.kobj, &m_compass_gr);
+}
+
+static const struct i2c_device_id hmc6352_id[] = {
+	{ "hmc6352" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, hmc6352_id);
+
+static struct i2c_driver hmc6352_driver = {
+	.driver = {
+		.name = "hmc6352",
+	},
+	.probe = hmc6352_probe,
+	.remove = hmc6352_remove,
+	.id_table = hmc6352_id,
+};
+
+module_i2c_driver(hmc6352_driver);
+
+MODULE_AUTHOR("Kalhan Trisal <kalhan.trisal@intel.com");
+MODULE_DESCRIPTION("hmc6352 Compass Driver");
+MODULE_LICENSE("GPL v2");