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, 82 insertions, 0 deletions

diff --git a/drivers/macintosh/macio_sysfs.c b/drivers/macintosh/macio_sysfs.c
new file mode 100644
index 000000000..2bbe359b2
--- /dev/null
+++ b/drivers/macintosh/macio_sysfs.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/stat.h>
+#include <asm/macio.h>
+
+static ssize_t
+compatible_show (struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct platform_device *of;
+	const char *compat;
+	int cplen;
+	int length = 0;
+
+	of = &to_macio_device (dev)->ofdev;
+	compat = of_get_property(of->dev.of_node, "compatible", &cplen);
+	if (!compat) {
+		*buf = '\0';
+		return 0;
+	}
+	while (cplen > 0) {
+		int l;
+		length += sprintf (buf, "%s\n", compat);
+		buf += length;
+		l = strlen (compat) + 1;
+		compat += l;
+		cplen -= l;
+	}
+
+	return length;
+}
+static DEVICE_ATTR_RO(compatible);
+
+static ssize_t modalias_show (struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	return of_device_modalias(dev, buf, PAGE_SIZE);
+}
+
+static ssize_t devspec_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct platform_device *ofdev;
+
+	ofdev = to_platform_device(dev);
+	return sprintf(buf, "%pOF\n", ofdev->dev.of_node);
+}
+static DEVICE_ATTR_RO(modalias);
+static DEVICE_ATTR_RO(devspec);
+
+static ssize_t name_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%pOFn\n", dev->of_node);
+}
+static DEVICE_ATTR_RO(name);
+
+static ssize_t type_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n", of_node_get_device_type(dev->of_node));
+}
+static DEVICE_ATTR_RO(type);
+
+static struct attribute *macio_dev_attrs[] = {
+	&dev_attr_name.attr,
+	&dev_attr_type.attr,
+	&dev_attr_compatible.attr,
+	&dev_attr_modalias.attr,
+	&dev_attr_devspec.attr,
+	NULL,
+};
+
+static const struct attribute_group macio_dev_group = {
+	.attrs = macio_dev_attrs,
+};
+
+const struct attribute_group *macio_dev_groups[] = {
+	&macio_dev_group,
+	NULL,
+};