gpiolib: cdev: replace strncpy() with strscpy()

Replace usage of strncpy() with strscpy() to remove -Wstringop-truncation
warnings.

The structures being populated are zeroed, to prevent stack leakage as
they are returned to userspace, so strscpy() performs the equivalent
function without the warnings.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/gpio/gpiolib-cdev.c

@@ -752,6 +752,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
 	bool ok_for_pinctrl;
 	unsigned long flags;
 
+	memset(info, 0, sizeof(*info));
 	info->line_offset = gpio_chip_hwgpio(desc);
 
 	/*
@@ -766,19 +767,11 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
 
 	spin_lock_irqsave(&gpio_lock, flags);
 
-	if (desc->name) {
-		strncpy(info->name, desc->name, sizeof(info->name));
-		info->name[sizeof(info->name) - 1] = '\0';
-	} else {
-		info->name[0] = '\0';
-	}
+	if (desc->name)
+		strscpy(info->name, desc->name, sizeof(info->name));
 
-	if (desc->label) {
-		strncpy(info->consumer, desc->label, sizeof(info->consumer));
-		info->consumer[sizeof(info->consumer) - 1] = '\0';
-	} else {
-		info->consumer[0] = '\0';
-	}
+	if (desc->label)
+		strscpy(info->consumer, desc->label, sizeof(info->consumer));
 
 	/*
 	 * Userspace only need to know that the kernel is using this GPIO so
@@ -842,12 +835,10 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
 		memset(&chipinfo, 0, sizeof(chipinfo));
 
-		strncpy(chipinfo.name, dev_name(&gdev->dev),
+		strscpy(chipinfo.name, dev_name(&gdev->dev),
 			sizeof(chipinfo.name));
-		chipinfo.name[sizeof(chipinfo.name)-1] = '\0';
-		strncpy(chipinfo.label, gdev->label,
+		strscpy(chipinfo.label, gdev->label,
 			sizeof(chipinfo.label));
-		chipinfo.label[sizeof(chipinfo.label)-1] = '\0';
 		chipinfo.lines = gdev->ngpio;
 		if (copy_to_user(ip, &chipinfo, sizeof(chipinfo)))
 			return -EFAULT;