From: Marcin Kościelnicki <mwk@0x04.net>
Date: Wed, 20 Nov 2019 23:20:15 +0000 (+0100)
Subject: rtld: Check __libc_enable_secure before honoring LD_PREFER_MAP_32BIT_EXEC (CVE-2019... 
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2626b15e88e00b5e9c8cc3962cf4768a5344f07a;p=thirdparty%2Fglibc.git

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").

(cherry picked from commit d5dfad4326fc683c813df1e37bbf5cf920591c8e)
Change-Id: Ib782573b4623ee3edfa9f98ad62f69b9d8edcb27
---

diff --git a/NEWS b/NEWS
index 5dc41ff3eb0..4ad7c47d5f4 100644
--- a/NEWS
+++ b/NEWS
@@ -35,6 +35,7 @@ The following bugs are resolved with this release:
   [24744] io: Remove the copy_file_range emulation
   [24986] alpha: new getegid, geteuid and getppid syscalls used
     unconditionally
+  [25204] Ignore LD_PREFER_MAP_32BIT_EXEC for SUID programs
 
 Security related changes:
 
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h b/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h
index 975cbe2950e..df2cdfdb6b3 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h
+++ b/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;