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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means that if an outdated routine has a bug that would otherwise not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
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