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, 103 insertions, 0 deletions

diff --git a/drivers/input/misc/ad714x-spi.c b/drivers/input/misc/ad714x-spi.c
new file mode 100644
index 000000000..eb13b4cd6
--- /dev/null
+++ b/drivers/input/misc/ad714x-spi.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AD714X CapTouch Programmable Controller driver (SPI bus)
+ *
+ * Copyright 2009-2011 Analog Devices Inc.
+ */
+
+#include <linux/input.h>	/* BUS_SPI */
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/pm.h>
+#include <linux/types.h>
+#include "ad714x.h"
+
+#define AD714x_SPI_CMD_PREFIX      0xE000   /* bits 15:11 */
+#define AD714x_SPI_READ            BIT(10)
+
+static int ad714x_spi_read(struct ad714x_chip *chip,
+			   unsigned short reg, unsigned short *data, size_t len)
+{
+	struct spi_device *spi = to_spi_device(chip->dev);
+	struct spi_message message;
+	struct spi_transfer xfer[2];
+	int i;
+	int error;
+
+	spi_message_init(&message);
+	memset(xfer, 0, sizeof(xfer));
+
+	chip->xfer_buf[0] = cpu_to_be16(AD714x_SPI_CMD_PREFIX |
+					AD714x_SPI_READ | reg);
+	xfer[0].tx_buf = &chip->xfer_buf[0];
+	xfer[0].len = sizeof(chip->xfer_buf[0]);
+	spi_message_add_tail(&xfer[0], &message);
+
+	xfer[1].rx_buf = &chip->xfer_buf[1];
+	xfer[1].len = sizeof(chip->xfer_buf[1]) * len;
+	spi_message_add_tail(&xfer[1], &message);
+
+	error = spi_sync(spi, &message);
+	if (unlikely(error)) {
+		dev_err(chip->dev, "SPI read error: %d\n", error);
+		return error;
+	}
+
+	for (i = 0; i < len; i++)
+		data[i] = be16_to_cpu(chip->xfer_buf[i + 1]);
+
+	return 0;
+}
+
+static int ad714x_spi_write(struct ad714x_chip *chip,
+			    unsigned short reg, unsigned short data)
+{
+	struct spi_device *spi = to_spi_device(chip->dev);
+	int error;
+
+	chip->xfer_buf[0] = cpu_to_be16(AD714x_SPI_CMD_PREFIX | reg);
+	chip->xfer_buf[1] = cpu_to_be16(data);
+
+	error = spi_write(spi, (u8 *)chip->xfer_buf,
+			  2 * sizeof(*chip->xfer_buf));
+	if (unlikely(error)) {
+		dev_err(chip->dev, "SPI write error: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static int ad714x_spi_probe(struct spi_device *spi)
+{
+	struct ad714x_chip *chip;
+	int err;
+
+	spi->bits_per_word = 8;
+	err = spi_setup(spi);
+	if (err < 0)
+		return err;
+
+	chip = ad714x_probe(&spi->dev, BUS_SPI, spi->irq,
+			    ad714x_spi_read, ad714x_spi_write);
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+
+	spi_set_drvdata(spi, chip);
+
+	return 0;
+}
+
+static struct spi_driver ad714x_spi_driver = {
+	.driver = {
+		.name	= "ad714x_captouch",
+		.pm	= pm_sleep_ptr(&ad714x_pm),
+	},
+	.probe		= ad714x_spi_probe,
+};
+
+module_spi_driver(ad714x_spi_driver);
+
+MODULE_DESCRIPTION("Analog Devices AD714X Capacitance Touch Sensor SPI Bus Driver");
+MODULE_AUTHOR("Barry Song <21cnbao@gmail.com>");
+MODULE_LICENSE("GPL");