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Partial backport (without the test) of:
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commit 1c1243b6fc33c029488add276e56570a07803bfd
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Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
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Date: Tue Mar 7 20:52:04 2017 +0530
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Ignore and remove LD_HWCAP_MASK for AT_SECURE programs (bug #21209)
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The LD_HWCAP_MASK environment variable may alter the selection of
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function variants for some architectures. For AT_SECURE process it
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means that if an outdated routine has a bug that would otherwise not
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affect newer platforms by default, LD_HWCAP_MASK will allow that bug
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to be exploited.
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To be on the safe side, ignore and disable LD_HWCAP_MASK for setuid
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binaries.
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[BZ #21209]
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* elf/rtld.c (process_envvars): Ignore LD_HWCAP_MASK for
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AT_SECURE processes.
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* sysdeps/generic/unsecvars.h: Add LD_HWCAP_MASK.
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* elf/tst-env-setuid.c (test_parent): Test LD_HWCAP_MASK.
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(test_child): Likewise.
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* elf/Makefile (tst-env-setuid-ENV): Add LD_HWCAP_MASK.
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Index: b/elf/rtld.c
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===================================================================
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--- a/elf/rtld.c
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+++ b/elf/rtld.c
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@@ -2688,7 +2688,8 @@ process_envvars (enum mode *modep)
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case 10:
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/* Mask for the important hardware capabilities. */
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- if (memcmp (envline, "HWCAP_MASK", 10) == 0)
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+ if (!__libc_enable_secure
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+ && memcmp (envline, "HWCAP_MASK", 10) == 0)
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GLRO(dl_hwcap_mask) = __strtoul_internal (&envline[11], NULL,
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0, 0);
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break;
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Index: b/sysdeps/generic/unsecvars.h
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===================================================================
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--- a/sysdeps/generic/unsecvars.h
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+++ b/sysdeps/generic/unsecvars.h
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@@ -9,6 +9,7 @@
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"LD_DEBUG\0" \
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"LD_DEBUG_OUTPUT\0" \
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"LD_DYNAMIC_WEAK\0" \
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+ "LD_HWCAP_MASK\0" \
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"LD_LIBRARY_PATH\0" \
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"LD_ORIGIN_PATH\0" \
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"LD_PRELOAD\0" \
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