File prefer-map-32bit-exec.patch of Package glibc.21322
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;
