diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 6911daa9f854..b409c42bfe6f 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -1624,6 +1624,8 @@ static long dmirror_fops_unlocked_ioctl(struct file *filp,
 
 	if (cmd.addr & ~PAGE_MASK)
 		return -EINVAL;
+	if (cmd.npages > ULONG_MAX >> PAGE_SHIFT)
+		return -EINVAL;
 	if (cmd.addr >= (cmd.addr + (cmd.npages << PAGE_SHIFT)))
 		return -EINVAL;