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, 72 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/ad7879-spi.c b/drivers/input/touchscreen/ad7879-spi.c
new file mode 100644
index 000000000..064968fe5
--- /dev/null
+++ b/drivers/input/touchscreen/ad7879-spi.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AD7879/AD7889 touchscreen (SPI bus)
+ *
+ * Copyright (C) 2008-2010 Michael Hennerich, Analog Devices Inc.
+ */
+
+#include <linux/input.h>	/* BUS_SPI */
+#include <linux/pm.h>
+#include <linux/spi/spi.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+#include "ad7879.h"
+
+#define AD7879_DEVID		0x7A	/* AD7879/AD7889 */
+
+#define MAX_SPI_FREQ_HZ      5000000
+
+#define AD7879_CMD_MAGIC     0xE0
+#define AD7879_CMD_READ      BIT(2)
+
+static const struct regmap_config ad7879_spi_regmap_config = {
+	.reg_bits = 16,
+	.val_bits = 16,
+	.max_register = 15,
+	.read_flag_mask = AD7879_CMD_MAGIC | AD7879_CMD_READ,
+	.write_flag_mask = AD7879_CMD_MAGIC,
+};
+
+static int ad7879_spi_probe(struct spi_device *spi)
+{
+	struct regmap *regmap;
+
+	/* don't exceed max specified SPI CLK frequency */
+	if (spi->max_speed_hz > MAX_SPI_FREQ_HZ) {
+		dev_err(&spi->dev, "SPI CLK %d Hz?\n", spi->max_speed_hz);
+		return -EINVAL;
+	}
+
+	regmap = devm_regmap_init_spi(spi, &ad7879_spi_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	return ad7879_probe(&spi->dev, regmap, spi->irq, BUS_SPI, AD7879_DEVID);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id ad7879_spi_dt_ids[] = {
+	{ .compatible = "adi,ad7879", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad7879_spi_dt_ids);
+#endif
+
+static struct spi_driver ad7879_spi_driver = {
+	.driver = {
+		.name		= "ad7879",
+		.dev_groups	= ad7879_groups,
+		.pm		= &ad7879_pm_ops,
+		.of_match_table	= of_match_ptr(ad7879_spi_dt_ids),
+	},
+	.probe		= ad7879_spi_probe,
+};
+
+module_spi_driver(ad7879_spi_driver);
+
+MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
+MODULE_DESCRIPTION("AD7879(-1) touchscreen SPI bus driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:ad7879");