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, 45 insertions, 0 deletions

diff --git a/drivers/hid/hid-macally.c b/drivers/hid/hid-macally.c
new file mode 100644
index 000000000..fe7576458
--- /dev/null
+++ b/drivers/hid/hid-macally.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  HID driver for quirky Macally devices
+ *
+ *  Copyright (c) 2019 Alex Henrie <alexhenrie24@gmail.com>
+ */
+
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+MODULE_AUTHOR("Alex Henrie <alexhenrie24@gmail.com>");
+MODULE_DESCRIPTION("Macally devices");
+MODULE_LICENSE("GPL");
+
+/*
+ * The Macally ikey keyboard says that its logical and usage maximums are both
+ * 101, but the power key is 102 and the equals key is 103
+ */
+static const __u8 *macally_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+					unsigned int *rsize)
+{
+	if (*rsize >= 60 && rdesc[53] == 0x65 && rdesc[59] == 0x65) {
+		hid_info(hdev,
+			"fixing up Macally ikey keyboard report descriptor\n");
+		rdesc[53] = rdesc[59] = 0x67;
+	}
+	return rdesc;
+}
+
+static const struct hid_device_id macally_id_table[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_SOLID_YEAR,
+			 USB_DEVICE_ID_MACALLY_IKEY_KEYBOARD) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, macally_id_table);
+
+static struct hid_driver macally_driver = {
+	.name			= "macally",
+	.id_table		= macally_id_table,
+	.report_fixup		= macally_report_fixup,
+};
+
+module_hid_driver(macally_driver);