[PATCH v2] acpi: battery: Sanitise model_number by dropping unprintable characters

[Kate Hsuan <hpa@redhat.com>]

The battery Embedded Controller (EC) may return the model name with
trailing unprintable or non-ASCII characters. For example, on some systems:

$ cat /sys/class/power_supply/BAT0/model_name
LNV-5B10W51864��

If a non-ASCII or an unprintable character is found, it will be replaced
with '\0' to ensure the model_number is a valid string. If left intact,
the malformed string prevents udev rules and hwdb working correctly.

Link: https://gitlab.freedesktop.org/upower/upower/-/work_items/345

Signed-off-by: Kate Hsuan <hpa@redhat.com>
---
 drivers/acpi/battery.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index f5e0eb299610..4409fb95b988 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -10,6 +10,7 @@
 
 #define pr_fmt(fmt) "ACPI: battery: " fmt
 
+#include <linux/ctype.h>
 #include <linux/delay.h>
 #include <linux/dmi.h>
 #include <linux/jiffies.h>
@@ -483,6 +484,15 @@ static int acpi_battery_get_status(struct acpi_battery *battery)
 	return 0;
 }
 
+static void acpi_battery_clean_unprintable_chars(char *str, size_t length)
+{
+	for (unsigned int i = 0; i < length; i++) {
+		if (!isascii(str[i]) || !isprint(str[i])) {
+			str[i] = '\0';
+			break;
+		}
+	}
+}
 
 static int extract_battery_info(const int use_bix,
 			 struct acpi_battery *battery,
@@ -524,6 +534,10 @@ static int extract_battery_info(const int use_bix,
 	    battery->capacity_now > battery->full_charge_capacity)
 		battery->capacity_now = battery->full_charge_capacity;
 
+	if (!result)
+		acpi_battery_clean_unprintable_chars(battery->model_number,
+					ARRAY_SIZE(battery->model_number));
+
 	return result;
 }
 
-- 
2.55.0