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/dio/dio-sysfs.c b/drivers/dio/dio-sysfs.c
new file mode 100644
index 000000000..ee1a3b59b
--- /dev/null
+++ b/drivers/dio/dio-sysfs.c
@@ -0,0 +1,82 @@
+/*
+ *  File Attributes for DIO Devices
+ *
+ *  Copyright (C) 2004 Jochen Friedrich
+ *
+ *  Loosely based on drivers/pci/pci-sysfs.c and drivers/zorro/zorro-sysfs.c
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of this archive
+ *  for more details.
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/dio.h>
+#include <linux/stat.h>
+
+/* show configuration fields */
+
+static ssize_t dio_show_id(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d;
+
+	d = to_dio_dev(dev);
+	return sprintf(buf, "0x%02x\n", (d->id & 0xff));
+}
+static DEVICE_ATTR(id, S_IRUGO, dio_show_id, NULL);
+
+static ssize_t dio_show_ipl(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d;
+
+	d = to_dio_dev(dev);
+	return sprintf(buf, "0x%02x\n", d->ipl);
+}
+static DEVICE_ATTR(ipl, S_IRUGO, dio_show_ipl, NULL);
+
+static ssize_t dio_show_secid(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d;
+
+	d = to_dio_dev(dev);
+	return sprintf(buf, "0x%02x\n", ((d->id >> 8)& 0xff));
+}
+static DEVICE_ATTR(secid, S_IRUGO, dio_show_secid, NULL);
+
+static ssize_t dio_show_name(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d;
+
+	d = to_dio_dev(dev);
+	return sprintf(buf, "%s\n", d->name);
+}
+static DEVICE_ATTR(name, S_IRUGO, dio_show_name, NULL);
+
+static ssize_t dio_show_resource(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dio_dev *d = to_dio_dev(dev);
+
+	return sprintf(buf, "0x%08lx 0x%08lx 0x%08lx\n",
+		       (unsigned long)dio_resource_start(d),
+		       (unsigned long)dio_resource_end(d),
+		       dio_resource_flags(d));
+}
+static DEVICE_ATTR(resource, S_IRUGO, dio_show_resource, NULL);
+
+int dio_create_sysfs_dev_files(struct dio_dev *d)
+{
+	struct device *dev = &d->dev;
+	int error;
+
+	/* current configuration's attributes */
+	if ((error = device_create_file(dev, &dev_attr_id)) ||
+	    (error = device_create_file(dev, &dev_attr_ipl)) ||
+	    (error = device_create_file(dev, &dev_attr_secid)) ||
+	    (error = device_create_file(dev, &dev_attr_name)) ||
+	    (error = device_create_file(dev, &dev_attr_resource)))
+		return error;
+
+	return 0;
+}
+