HID: battery: don't do DMA from stack

Instead of using data from stack for DMA in hidinput_get_battery_property(),
allocate the buffer dynamically.

Cc: stable@kernel.org
Reported-by: Richard Ryniker <ryniker@alum.mit.edu>
Reported-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-input.c

@@ -340,7 +340,7 @@ static int hidinput_get_battery_property(struct power_supply *psy,
 {
 	struct hid_device *dev = container_of(psy, struct hid_device, battery);
 	int ret = 0;
-	__u8 buf[2] = {};
+	__u8 *buf;
 
 	switch (prop) {
 	case POWER_SUPPLY_PROP_PRESENT:
@@ -349,12 +349,19 @@ static int hidinput_get_battery_property(struct power_supply *psy,
 		break;
 
 	case POWER_SUPPLY_PROP_CAPACITY:
+
+		buf = kmalloc(2 * sizeof(__u8), GFP_KERNEL);
+		if (!buf) {
+			ret = -ENOMEM;
+			break;
+		}
 		ret = dev->hid_get_raw_report(dev, dev->battery_report_id,
-					      buf, sizeof(buf),
+					      buf, 2,
 					      dev->battery_report_type);
 
 		if (ret != 2) {
 			ret = -ENODATA;
+			kfree(buf);
 			break;
 		}
 		ret = 0;
@@ -364,6 +371,7 @@ static int hidinput_get_battery_property(struct power_supply *psy,
 		    buf[1] <= dev->battery_max)
 			val->intval = (100 * (buf[1] - dev->battery_min)) /
 				(dev->battery_max - dev->battery_min);
+		kfree(buf);
 		break;
 
 	case POWER_SUPPLY_PROP_MODEL_NAME: