File prefer-map-32bit-exec.patch of Package glibc.18276

From d5dfad4326fc683c813df1e37bbf5cf920591c8e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcin=20Ko=C5=9Bcielnicki?= <mwk@0x04.net>
Date: Thu, 21 Nov 2019 00:20:15 +0100
Subject: [PATCH] rtld: Check __libc_enable_secure before honoring
 LD_PREFER_MAP_32BIT_EXEC (CVE-2019-19126) [BZ #25204]

The problem was introduced in glibc 2.23, in commit
b9eb92ab05204df772eb4929eccd018637c9f3e9
("Add Prefer_MAP_32BIT_EXEC to map executable pages with MAP_32BIT").
---
 NEWS                                            | 6 +++++-
 sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h | 3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

Index: glibc-2.26/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h
===================================================================
--- glibc-2.26.orig/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h
+++ glibc-2.26/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h
@@ -31,7 +31,8 @@
    environment variable, LD_PREFER_MAP_32BIT_EXEC.  */
 #define EXTRA_LD_ENVVARS \
   case 21:								  \
-    if (memcmp (envline, "PREFER_MAP_32BIT_EXEC", 21) == 0)		  \
+    if (!__libc_enable_secure						  \
+	&& memcmp (envline, "PREFER_MAP_32BIT_EXEC", 21) == 0)		  \
       GLRO(dl_x86_cpu_features).feature[index_arch_Prefer_MAP_32BIT_EXEC] \
 	|= bit_arch_Prefer_MAP_32BIT_EXEC;				  \
     break;
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