diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
index 0bfc14041bbb4d..b63b548497c14a 100644
--- a/arch/x86/kernel/cpu/mce/inject.c
+++ b/arch/x86/kernel/cpu/mce/inject.c
@@ -350,7 +350,7 @@ static ssize_t flags_write(struct file *filp, const char __user *ubuf,
 	char buf[MAX_FLAG_OPT_SIZE], *__buf;
 	int err;
 
-	if (cnt > MAX_FLAG_OPT_SIZE)
+	if (!cnt || cnt > MAX_FLAG_OPT_SIZE)
 		return -EINVAL;
 
 	if (copy_from_user(&buf, ubuf, cnt))