gpio: mockup: improve the debugfs input sanitization

We're currently only checking the first character of the input to the
debugfs event files, so a string like '0sdfdsf' is valid and indicates
a falling edge event.

Be more strict and only allow '0', '1', '0\n' & '1\n'.

While we're at it: move the sanitization code before the irq_enabled
check so that we indicate an error on invalid input even if nobody is
waiting for events.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
index ba8d62aa801a878733129da27a79cef5219a4673..da76267aa85cdabb4a2d8310b4e5bece48a59573 100644 (file)
--- a/drivers/gpio/gpio-mockup.c
+++ b/drivers/gpio/gpio-mockup.c
@@ -208,8 +208,7 @@ static ssize_t gpio_mockup_event_write(struct file *file,
        struct seq_file *sfile;
        struct gpio_desc *desc;
        struct gpio_chip *gc;
-       int val;
-       char buf;
+       int rv, val;
 
        sfile = file->private_data;
        priv = sfile->private;
@@ -217,19 +216,15 @@ static ssize_t gpio_mockup_event_write(struct file *file,
        chip = priv->chip;
        gc = &chip->gc;
 
+       rv = kstrtoint_from_user(usr_buf, size, 0, &val);
+       if (rv)
+               return rv;
+       if (val != 0 && val != 1)
+               return -EINVAL;
+
        if (!chip->lines[priv->offset].irq_enabled)
                return size;
 
-       if (copy_from_user(&buf, usr_buf, 1))
-               return -EFAULT;
-
-       if (buf == '0')
-               val = 0;
-       else if (buf == '1')
-               val = 1;
-       else
-               return -EINVAL;
-
        gpiod_set_value_cansleep(desc, val);
        priv->chip->irq_ctx.irq = gc->irq_base + priv->offset;
        irq_work_queue(&priv->chip->irq_ctx.work);