HID: logitech-hidpp: check name retrieval return code

hidpp_devicenametype_get_device_name() may return a negative value on
protocol errors (for example, when the device is powered off).
Explicitly check this condition to avoid a long-running loop.

(0 cannot be returned as __name_length - index > 0, but check for it
anyway as it would otherwise result in an infinite loop.)

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 5066df8afee5f3cdb2e2795340ef011e50a8d3f2..4d72c20fa233427e46de1655178cd850398e7da2 100644 (file)
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -484,10 +484,16 @@ static char *hidpp_get_device_name(struct hidpp_device *hidpp)
        if (!name)
                return NULL;
 
-       while (index < __name_length)
-               index += hidpp_devicenametype_get_device_name(hidpp,
+       while (index < __name_length) {
+               ret = hidpp_devicenametype_get_device_name(hidpp,
                        feature_index, index, name + index,
                        __name_length - index);
+               if (ret <= 0) {
+                       kfree(name);
+                       return NULL;
+               }
+               index += ret;
+       }
 
        return name;
 }