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, 51 insertions, 0 deletions

diff --git a/drivers/hid/hid-keytouch.c b/drivers/hid/hid-keytouch.c
new file mode 100644
index 000000000..b9abd53a5
--- /dev/null
+++ b/drivers/hid/hid-keytouch.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for Keytouch devices not fully compliant with HID standard
+ *
+ *  Copyright (c) 2011 Jiri Kosina
+ */
+
+/*
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+/* Replace the broken report descriptor of this device with rather
+ * a default one */
+static const __u8 keytouch_fixed_rdesc[] = {
+0x05, 0x01, 0x09, 0x06, 0xa1, 0x01, 0x05, 0x07, 0x19, 0xe0, 0x29, 0xe7, 0x15,
+0x00, 0x25, 0x01, 0x75, 0x01, 0x95, 0x08, 0x81, 0x02, 0x95, 0x01, 0x75, 0x08,
+0x81, 0x01, 0x95, 0x03, 0x75, 0x01, 0x05, 0x08, 0x19, 0x01, 0x29, 0x03, 0x91,
+0x02, 0x95, 0x05, 0x75, 0x01, 0x91, 0x01, 0x95, 0x06, 0x75, 0x08, 0x15, 0x00,
+0x26, 0xff, 0x00, 0x05, 0x07, 0x19, 0x00, 0x2a, 0xff, 0x00, 0x81, 0x00, 0xc0
+};
+
+static const __u8 *keytouch_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	hid_info(hdev, "fixing up Keytouch IEC report descriptor\n");
+
+	*rsize = sizeof(keytouch_fixed_rdesc);
+	return keytouch_fixed_rdesc;
+}
+
+static const struct hid_device_id keytouch_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_KEYTOUCH, USB_DEVICE_ID_KEYTOUCH_IEC) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, keytouch_devices);
+
+static struct hid_driver keytouch_driver = {
+	.name = "keytouch",
+	.id_table = keytouch_devices,
+	.report_fixup = keytouch_report_fixup,
+};
+module_hid_driver(keytouch_driver);
+
+MODULE_DESCRIPTION("HID driver for Keytouch devices not fully compliant with HID standard");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jiri Kosina");