From 3776f38fcd267c127ba5eb222e2c614c191744aa Mon Sep 17 00:00:00 2001
From: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date: Tue, 20 Jun 2017 05:59:17 +0200
Subject: [PATCH] Ignore and remove LD_HWCAP_MASK for AT_SECURE programs (bug
 #21209)

The LD_HWCAP_MASK environment variable may alter the selection of
function variants for some architectures.  For AT_SECURE process it
means that if an outdated routine has a bug that would otherwise not
affect newer platforms by default, LD_HWCAP_MASK will allow that bug
to be exploited.

To be on the safe side, ignore and disable LD_HWCAP_MASK for setuid
binaries.

	[BZ #21209]
	* elf/rtld.c (process_envvars): Ignore LD_HWCAP_MASK for
	AT_SECURE processes.
	* sysdeps/generic/unsecvars.h: Add LD_HWCAP_MASK.

(cherry picked from commit 1c1243b6fc33c029488add276e56570a07803bfd)

diff --git a/elf/rtld.c b/elf/rtld.c
index 369724b..9362a21 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -2534,7 +2534,8 @@ process_envvars (enum mode *modep)
 
 	case 10:
 	  /* Mask for the important hardware capabilities.  */
-	  if (memcmp (envline, "HWCAP_MASK", 10) == 0)
+	  if (!__libc_enable_secure
+	      && memcmp (envline, "HWCAP_MASK", 10) == 0)
 	    GLRO(dl_hwcap_mask) = __strtoul_internal (&envline[11], NULL,
 						      0, 0);
 	  break;
diff --git a/sysdeps/generic/unsecvars.h b/sysdeps/generic/unsecvars.h
index a740837..5ea8a4a 100644
--- a/sysdeps/generic/unsecvars.h
+++ b/sysdeps/generic/unsecvars.h
@@ -16,6 +16,7 @@
   "LD_DEBUG\0"								      \
   "LD_DEBUG_OUTPUT\0"							      \
   "LD_DYNAMIC_WEAK\0"							      \
+  "LD_HWCAP_MASK\0"							      \
   "LD_LIBRARY_PATH\0"							      \
   "LD_ORIGIN_PATH\0"							      \
   "LD_PRELOAD\0"							      \
-- 
2.9.3