diff --git a/mm/fadvise.c b/mm/fadvise.c
index 3bcfd81db45e..ebc997752d1c 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -66,8 +66,12 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
 		goto out;
 	}
 
-	/* Careful about overflows. Len == 0 means "as much as possible" */
-	endbyte = offset + len;
+	/*
+	 * Careful about overflows. Len == 0 means "as much as possible".  Use
+	 * unsigned math because signed overflows are undefined and UBSan
+	 * complains.
+	 */
+	endbyte = (u64)offset + (u64)len;
 	if (!len || endbyte < len)
 		endbyte = -1;
 	else