diff --git a/drivers/usb/atm/cxacru.c b/drivers/usb/atm/cxacru.c
index 1173f9cbc137ef1b175a84de7d2c8c81219323f5..0a866e90b49c80ee04061ae1af3ac5020dd3a237 100644
--- a/drivers/usb/atm/cxacru.c
+++ b/drivers/usb/atm/cxacru.c
@@ -476,6 +476,8 @@ static ssize_t cxacru_sysfs_store_adsl_config(struct device *dev,
 			return -EINVAL;
 		if (index < 0 || index > 0x7f)
 			return -EINVAL;
+		if (tmp < 0 || tmp > len - pos)
+			return -EINVAL;
 		pos += tmp;
 
 		/* skip trailing newline */