diff --git a/fs/libfs.c b/fs/libfs.c
index 4bb80685ee6e29f9eca702eaf0c415833812bd30..608566e38d12477d48b1b47d3b89ba7e2a084ab3 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -934,7 +934,7 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
 			  size_t len, loff_t *ppos)
 {
 	struct simple_attr *attr;
-	u64 val;
+	unsigned long long val;
 	size_t size;
 	ssize_t ret;
 
@@ -952,7 +952,9 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
 		goto out;
 
 	attr->set_buf[size] = '\0';
-	val = simple_strtoll(attr->set_buf, NULL, 0);
+	ret = kstrtoull(attr->set_buf, 0, &val);
+	if (ret)
+		goto out;
 	ret = attr->set(attr->data, val);
 	if (ret == 0)
 		ret = len; /* on success, claim we got the whole input */