diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
index fa9f7ff4a3a6a506f4918f6838f96e5b1cc35d9a..4058e024109171b78483a841b6aad58aea7e0b8b 100644
--- a/drivers/acpi/custom_method.c
+++ b/drivers/acpi/custom_method.c
@@ -42,6 +42,8 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
 				   sizeof(struct acpi_table_header)))
 			return -EFAULT;
 		uncopied_bytes = max_size = table.length;
+		/* make sure the buf is not allocated */
+		kfree(buf);
 		buf = kzalloc(max_size, GFP_KERNEL);
 		if (!buf)
 			return -ENOMEM;