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>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 5066df8afee5..4d72c20fa233 100644
--- 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;
 }