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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
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means that if an outdated routine has a bug that would otherwise not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.
	* elf/tst-env-setuid.c (test_parent): Test LD_HWCAP_MASK.
	(test_child): Likewise.
	* elf/Makefile (tst-env-setuid-ENV): Add LD_HWCAP_MASK.
This commit is contained in:
Siddhesh Poyarekar 2017-03-07 20:52:04 +05:30
parent a7055e5935
commit 1c1243b6fc
5 changed files with 27 additions and 2 deletions
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10
ChangeLog
View file

@ -1,3 +1,13 @@
2017-03-07 Siddhesh Poyarekar <siddhesh@sourceware.org>
[BZ #21209]
* elf/rtld.c (process_envvars): Ignore LD_HWCAP_MASK for
AT_SECURE processes.
* sysdeps/generic/unsecvars.h: Add LD_HWCAP_MASK.
* elf/tst-env-setuid.c (test_parent): Test LD_HWCAP_MASK.
(test_child): Likewise.
* elf/Makefile (tst-env-setuid-ENV): Add LD_HWCAP_MASK.
2017-03-07 Adhemerval Zanella <adhemerval.zanella@linaro.org>
* sysdeps/unix/sysv/linux/hppa/ipc_priv.h: New file.

3
elf/Makefile
View file

@ -1398,6 +1398,7 @@ $(objpfx)tst-nodelete-dlclose: $(objpfx)tst-nodelete-dlclose-dso.so
$(objpfx)tst-nodelete-dlclose.out: $(objpfx)tst-nodelete-dlclose-dso.so \
$(objpfx)tst-nodelete-dlclose-plugin.so
tst-env-setuid-ENV = MALLOC_CHECK_=2 MALLOC_MMAP_THRESHOLD_=4096
tst-env-setuid-ENV = MALLOC_CHECK_=2 MALLOC_MMAP_THRESHOLD_=4096 \
LD_HWCAP_MASK=0xffffffff
tst-env-setuid-tunables-ENV = \
GLIBC_TUNABLES=glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096

3
elf/rtld.c
View file

@ -2404,7 +2404,8 @@ 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;

12
elf/tst-env-setuid.c
View file

@ -213,6 +213,12 @@ test_child (void)
return 1;
}
if (getenv ("LD_HWCAP_MASK") != NULL)
{
printf ("LD_HWCAP_MASK still set\n");
return 1;
}
return 0;
}
#endif
@ -233,6 +239,12 @@ test_parent (void)
return 1;
}
if (getenv ("LD_HWCAP_MASK") == NULL)
{
printf ("LD_HWCAP_MASK lost\n");
return 1;
}
return 0;
}
#endif

1
sysdeps/generic/unsecvars.h
View file

@ -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" \