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, 74 insertions, 0 deletions

diff --git a/drivers/hid/hid-primax.c b/drivers/hid/hid-primax.c
new file mode 100644
index 000000000..8db054280
--- /dev/null
+++ b/drivers/hid/hid-primax.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * HID driver for primax and similar keyboards with in-band modifiers
+ *
+ * Copyright 2011 Google Inc. All Rights Reserved
+ *
+ * Author:
+ *	Terry Lambert <tlambert@google.com>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+static int px_raw_event(struct hid_device *hid, struct hid_report *report,
+	 u8 *data, int size)
+{
+	int idx = size;
+
+	switch (report->id) {
+	case 0:		/* keyboard input */
+		/*
+		 * Convert in-band modifier key values into out of band
+		 * modifier bits and pull the key strokes from the report.
+		 * Thus a report data set which looked like:
+		 *
+		 * [00][00][E0][30][00][00][00][00]
+		 * (no modifier bits + "Left Shift" key + "1" key)
+		 *
+		 * Would be converted to:
+		 *
+		 * [01][00][00][30][00][00][00][00]
+		 * (Left Shift modifier bit + "1" key)
+		 *
+		 * As long as it's in the size range, the upper level
+		 * drivers don't particularly care if there are in-band
+		 * 0-valued keys, so they don't stop parsing.
+		 */
+		while (--idx > 1) {
+			if (data[idx] < 0xE0 || data[idx] > 0xE7)
+				continue;
+			data[0] |= (1 << (data[idx] - 0xE0));
+			data[idx] = 0;
+		}
+		hid_report_raw_event(hid, HID_INPUT_REPORT, data, size, size, 0);
+		return 1;
+
+	default:	/* unknown report */
+		/* Unknown report type; pass upstream */
+		hid_info(hid, "unknown report type %d\n", report->id);
+		break;
+	}
+
+	return 0;
+}
+
+static const struct hid_device_id px_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_PRIMAX, USB_DEVICE_ID_PRIMAX_KEYBOARD) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, px_devices);
+
+static struct hid_driver px_driver = {
+	.name = "primax",
+	.id_table = px_devices,
+	.raw_event = px_raw_event,
+};
+module_hid_driver(px_driver);
+
+MODULE_AUTHOR("Terry Lambert <tlambert@google.com>");
+MODULE_DESCRIPTION("HID driver for primax and similar keyboards with in-band modifiers");
+MODULE_LICENSE("GPL");