From 93dda65354e502e8b8db07f85b668710dd0aac68 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=83=AD=E4=BC=9F=E5=85=89?= <warriorguo@gmail.com>
Date: Mon, 21 Mar 2022 20:20:23 +0800
Subject: [PATCH] config rewrite failed save errno in case of being tainted
 (#10461)

errno would be potentially tainted during the serverLog() by the file io functions, such as fopen and fflush.
---
 src/config.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/config.c b/src/config.c
index 182da1961..c45cf3ff0 100644
--- a/src/config.c
+++ b/src/config.c
@@ -3033,8 +3033,10 @@ void configRewriteCommand(client *c) {
         return;
     }
     if (rewriteConfig(server.configfile, 0) == -1) {
-        serverLog(LL_WARNING,"CONFIG REWRITE failed: %s", strerror(errno));
-        addReplyErrorFormat(c,"Rewriting config file: %s", strerror(errno));
+        /* save errno in case of being tainted. */
+        int err = errno;
+        serverLog(LL_WARNING,"CONFIG REWRITE failed: %s", strerror(err));
+        addReplyErrorFormat(c,"Rewriting config file: %s", strerror(err));
     } else {
         serverLog(LL_WARNING,"CONFIG REWRITE executed with success.");
         addReply(c,shared.ok);