From 90b9900dc159efb63feee9b0995cc5d56aef6d75 Mon Sep 17 00:00:00 2001
From: Yusuke Endoh <mame@ruby-lang.org>
Date: Sun, 13 Oct 2019 00:49:18 +0900
Subject: [PATCH] io.c (rb_update_max_fd): fail with a negative file descripter

Coverity Scan points out that ext/socket/unixsocket.c may pass -1 to
rb_update_max_fd.  I'm unsure whether it can happen actually or not, but
it would be good for the function to reject a negative value.
---
 io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io.c b/io.c
index 33350ea752..eccd429352 100644
--- a/io.c
+++ b/io.c
@@ -201,7 +201,7 @@ rb_update_max_fd(int fd)
     rb_atomic_t max_fd = max_file_descriptor;
     int err;
 
-    if (afd <= max_fd)
+    if (fd < 0 || afd <= max_fd)
         return;
 
 #if defined(HAVE_FCNTL) && defined(F_GETFL)