diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index 9b646cb..ff43d6d 100644
--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -610,10 +610,14 @@ static long zonefs_fname_to_fno(const struct qstr *fname)
 		return c - '0';
 
 	for (i = 0, rname = name + len - 1; i < len; i++, rname--) {
+		long digit;
+
 		c = *rname;
 		if (!isdigit(c))
 			return -ENOENT;
-		fno += (c - '0') * shift;
+		digit = (c - '0') * shift;
+		if (check_add_overflow(fno, digit, &fno))
+			return -ENOENT;
 		shift *= 10;
 	}