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, 160 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ds1672.c b/drivers/rtc/rtc-ds1672.c
new file mode 100644
index 000000000..c610beb55
--- /dev/null
+++ b/drivers/rtc/rtc-ds1672.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * An rtc/i2c driver for the Dallas DS1672
+ * Copyright 2005-06 Tower Technologies
+ *
+ * Author: Alessandro Zummo <a.zummo@towertech.it>
+ */
+
+#include <linux/i2c.h>
+#include <linux/rtc.h>
+#include <linux/module.h>
+
+/* Registers */
+
+#define DS1672_REG_CNT_BASE	0
+#define DS1672_REG_CONTROL	4
+#define DS1672_REG_TRICKLE	5
+
+#define DS1672_REG_CONTROL_EOSC	0x80
+
+/*
+ * In the routines that deal directly with the ds1672 hardware, we use
+ * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch
+ * Time is set to UTC.
+ */
+static int ds1672_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	unsigned long time;
+	unsigned char addr = DS1672_REG_CONTROL;
+	unsigned char buf[4];
+
+	struct i2c_msg msgs[] = {
+		{/* setup read ptr */
+			.addr = client->addr,
+			.len = 1,
+			.buf = &addr
+		},
+		{/* read date */
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = 1,
+			.buf = buf
+		},
+	};
+
+	/* read control register */
+	if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {
+		dev_warn(&client->dev, "Unable to read the control register\n");
+		return -EIO;
+	}
+
+	if (buf[0] & DS1672_REG_CONTROL_EOSC) {
+		dev_warn(&client->dev, "Oscillator not enabled. Set time to enable.\n");
+		return -EINVAL;
+	}
+
+	addr = DS1672_REG_CNT_BASE;
+	msgs[1].len = 4;
+
+	/* read date registers */
+	if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {
+		dev_err(&client->dev, "%s: read error\n", __func__);
+		return -EIO;
+	}
+
+	dev_dbg(&client->dev,
+		"%s: raw read data - counters=%02x,%02x,%02x,%02x\n",
+		__func__, buf[0], buf[1], buf[2], buf[3]);
+
+	time = ((unsigned long)buf[3] << 24) | (buf[2] << 16) |
+	       (buf[1] << 8) | buf[0];
+
+	rtc_time64_to_tm(time, tm);
+
+	dev_dbg(&client->dev, "%s: tm is %ptR\n", __func__, tm);
+
+	return 0;
+}
+
+static int ds1672_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	int xfer;
+	unsigned char buf[6];
+	unsigned long secs = rtc_tm_to_time64(tm);
+
+	buf[0] = DS1672_REG_CNT_BASE;
+	buf[1] = secs & 0x000000FF;
+	buf[2] = (secs & 0x0000FF00) >> 8;
+	buf[3] = (secs & 0x00FF0000) >> 16;
+	buf[4] = (secs & 0xFF000000) >> 24;
+	buf[5] = 0;		/* set control reg to enable counting */
+
+	xfer = i2c_master_send(client, buf, 6);
+	if (xfer != 6) {
+		dev_err(&client->dev, "%s: send: %d\n", __func__, xfer);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static const struct rtc_class_ops ds1672_rtc_ops = {
+	.read_time = ds1672_read_time,
+	.set_time = ds1672_set_time,
+};
+
+static int ds1672_probe(struct i2c_client *client)
+{
+	int err = 0;
+	struct rtc_device *rtc;
+
+	dev_dbg(&client->dev, "%s\n", __func__);
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	rtc = devm_rtc_allocate_device(&client->dev);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	rtc->ops = &ds1672_rtc_ops;
+	rtc->range_max = U32_MAX;
+
+	err = devm_rtc_register_device(rtc);
+	if (err)
+		return err;
+
+	i2c_set_clientdata(client, rtc);
+
+	return 0;
+}
+
+static const struct i2c_device_id ds1672_id[] = {
+	{ .name = "ds1672" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ds1672_id);
+
+static const __maybe_unused struct of_device_id ds1672_of_match[] = {
+	{ .compatible = "dallas,ds1672" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ds1672_of_match);
+
+static struct i2c_driver ds1672_driver = {
+	.driver = {
+		   .name = "rtc-ds1672",
+		   .of_match_table = of_match_ptr(ds1672_of_match),
+	},
+	.probe = ds1672_probe,
+	.id_table = ds1672_id,
+};
+
+module_i2c_driver(ds1672_driver);
+
+MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
+MODULE_DESCRIPTION("Dallas/Maxim DS1672 timekeeper driver");
+MODULE_LICENSE("GPL");