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, 133 insertions, 0 deletions

diff --git a/drivers/reset/reset-zynq.c b/drivers/reset/reset-zynq.c
new file mode 100644
index 000000000..688b51288
--- /dev/null
+++ b/drivers/reset/reset-zynq.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015, National Instruments Corp.
+ *
+ * Xilinx Zynq Reset controller driver
+ *
+ * Author: Moritz Fischer <moritz.fischer@ettus.com>
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+struct zynq_reset_data {
+	struct regmap *slcr;
+	struct reset_controller_dev rcdev;
+	u32 offset;
+};
+
+#define to_zynq_reset_data(p)		\
+	container_of((p), struct zynq_reset_data, rcdev)
+
+static int zynq_reset_assert(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
+
+	int bank = id / BITS_PER_LONG;
+	int offset = id % BITS_PER_LONG;
+
+	pr_debug("%s: %s reset bank %u offset %u\n", KBUILD_MODNAME, __func__,
+		 bank, offset);
+
+	return regmap_update_bits(priv->slcr,
+				  priv->offset + (bank * 4),
+				  BIT(offset),
+				  BIT(offset));
+}
+
+static int zynq_reset_deassert(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
+
+	int bank = id / BITS_PER_LONG;
+	int offset = id % BITS_PER_LONG;
+
+	pr_debug("%s: %s reset bank %u offset %u\n", KBUILD_MODNAME, __func__,
+		 bank, offset);
+
+	return regmap_update_bits(priv->slcr,
+				  priv->offset + (bank * 4),
+				  BIT(offset),
+				  ~BIT(offset));
+}
+
+static int zynq_reset_status(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
+
+	int bank = id / BITS_PER_LONG;
+	int offset = id % BITS_PER_LONG;
+	int ret;
+	u32 reg;
+
+	pr_debug("%s: %s reset bank %u offset %u\n", KBUILD_MODNAME, __func__,
+		 bank, offset);
+
+	ret = regmap_read(priv->slcr, priv->offset + (bank * 4), &reg);
+	if (ret)
+		return ret;
+
+	return !!(reg & BIT(offset));
+}
+
+static const struct reset_control_ops zynq_reset_ops = {
+	.assert		= zynq_reset_assert,
+	.deassert	= zynq_reset_deassert,
+	.status		= zynq_reset_status,
+};
+
+static int zynq_reset_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct zynq_reset_data *priv;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->slcr = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
+						     "syscon");
+	if (IS_ERR(priv->slcr)) {
+		dev_err(&pdev->dev, "unable to get zynq-slcr regmap");
+		return PTR_ERR(priv->slcr);
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "missing IO resource\n");
+		return -ENODEV;
+	}
+
+	priv->offset = res->start;
+
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.nr_resets = resource_size(res) / 4 * BITS_PER_LONG;
+	priv->rcdev.ops = &zynq_reset_ops;
+	priv->rcdev.of_node = pdev->dev.of_node;
+
+	return devm_reset_controller_register(&pdev->dev, &priv->rcdev);
+}
+
+static const struct of_device_id zynq_reset_dt_ids[] = {
+	{ .compatible = "xlnx,zynq-reset", },
+	{ /* sentinel */ },
+};
+
+static struct platform_driver zynq_reset_driver = {
+	.probe	= zynq_reset_probe,
+	.driver = {
+		.name		= KBUILD_MODNAME,
+		.of_match_table	= zynq_reset_dt_ids,
+	},
+};
+builtin_platform_driver(zynq_reset_driver);