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, 88 insertions, 0 deletions

diff --git a/drivers/hid/hid-picolcd_lcd.c b/drivers/hid/hid-picolcd_lcd.c
new file mode 100644
index 000000000..318f19eac
--- /dev/null
+++ b/drivers/hid/hid-picolcd_lcd.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/***************************************************************************
+ *   Copyright (C) 2010-2012 by Bruno Prémont <bonbons@linux-vserver.org>  *
+ *                                                                         *
+ *   Based on Logitech G13 driver (v0.4)                                   *
+ *     Copyright (C) 2009 by Rick L. Vinyard, Jr. <rvinyard@cs.nmsu.edu>   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include <linux/hid.h>
+
+#include <linux/fb.h>
+#include <linux/lcd.h>
+
+#include "hid-picolcd.h"
+
+/*
+ * lcd class device
+ */
+static int picolcd_get_contrast(struct lcd_device *ldev)
+{
+	struct picolcd_data *data = lcd_get_data(ldev);
+	return data->lcd_contrast;
+}
+
+static int picolcd_set_contrast(struct lcd_device *ldev, int contrast)
+{
+	struct picolcd_data *data = lcd_get_data(ldev);
+	struct hid_report *report = picolcd_out_report(REPORT_CONTRAST, data->hdev);
+	unsigned long flags;
+
+	if (!report || report->maxfield != 1 || report->field[0]->report_count != 1)
+		return -ENODEV;
+
+	data->lcd_contrast = contrast & 0x0ff;
+	spin_lock_irqsave(&data->lock, flags);
+	hid_set_field(report->field[0], 0, data->lcd_contrast);
+	if (!(data->status & PICOLCD_FAILED))
+		hid_hw_request(data->hdev, report, HID_REQ_SET_REPORT);
+	spin_unlock_irqrestore(&data->lock, flags);
+	return 0;
+}
+
+static const struct lcd_ops picolcd_lcdops = {
+	.get_contrast   = picolcd_get_contrast,
+	.set_contrast   = picolcd_set_contrast,
+};
+
+int picolcd_init_lcd(struct picolcd_data *data, struct hid_report *report)
+{
+	struct device *dev = &data->hdev->dev;
+	struct lcd_device *ldev;
+
+	if (!report)
+		return -ENODEV;
+	if (report->maxfield != 1 || report->field[0]->report_count != 1 ||
+			report->field[0]->report_size != 8) {
+		dev_err(dev, "unsupported CONTRAST report");
+		return -EINVAL;
+	}
+
+	ldev = lcd_device_register(dev_name(dev), dev, data, &picolcd_lcdops);
+	if (IS_ERR(ldev)) {
+		dev_err(dev, "failed to register LCD\n");
+		return PTR_ERR(ldev);
+	}
+	ldev->props.max_contrast = 0x0ff;
+	data->lcd_contrast = 0xe5;
+	data->lcd = ldev;
+	picolcd_set_contrast(ldev, 0xe5);
+	return 0;
+}
+
+void picolcd_exit_lcd(struct picolcd_data *data)
+{
+	struct lcd_device *ldev = data->lcd;
+
+	data->lcd = NULL;
+	lcd_device_unregister(ldev);
+}
+
+int picolcd_resume_lcd(struct picolcd_data *data)
+{
+	if (!data->lcd)
+		return 0;
+	return picolcd_set_contrast(data->lcd, data->lcd_contrast);
+}
+