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[PATCH] Ignore and remove LD_HWCAP_MASK for AT_SECURE programs (bug #21209)
- From: Siddhesh Poyarekar <siddhesh at sourceware dot org>
- To: libc-alpha at sourceware dot org
- Cc: fweimer at redhat dot com
- Date: Thu, 2 Mar 2017 15:29:00 +0530
- Subject: [PATCH] Ignore and remove LD_HWCAP_MASK for AT_SECURE programs (bug #21209)
- Authentication-results: sourceware.org; auth=none
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means that if an outdated routine has a bug that would otherwise not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.
---
elf/Makefile | 3 ++-
elf/rtld.c | 3 ++-
elf/tst-env-setuid.c | 12 ++++++++++++
sysdeps/generic/unsecvars.h | 1 +
4 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/elf/Makefile b/elf/Makefile
index 61abeb5..cc4aeb2 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -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
diff --git a/elf/rtld.c b/elf/rtld.c
index a036ece..5986eaf 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -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;
diff --git a/elf/tst-env-setuid.c b/elf/tst-env-setuid.c
index 6ec3fa5..eec408e 100644
--- a/elf/tst-env-setuid.c
+++ b/elf/tst-env-setuid.c
@@ -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
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" \
--
2.7.4