elf: Refuse to dlopen PIE objects [BZ #24323]

Another executable has already been mapped, so the dynamic linker
cannot perform relocations correctly for the second executable.
This commit is contained in:
Florian Weimer 2019-06-18 16:42:10 +02:00
parent 02d8b5ab1c
commit 2c75b545de
5 changed files with 79 additions and 6 deletions

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@ -1,3 +1,15 @@
2019-06-18 Florian Weimer <fweimer@redhat.com>
[BZ #24323]
* include/elf.h (DT_1_SUPPORTED_MASK): Include DF_1_PIE.
* elf/dl-load.c (_dl_map_object_from_fd): Check for DF_1_PIE and
fail when called from dlopen.
* elf/Makefile [have-fpie && build-shared] (tests): Add
tst-dlopen-pie.
(tst-dlopen-pie): Link with -ldl.
(tst-dlopen-pie.out): Add run-time dependency on tst-pie1.
* elf/tst-dlopen-pie.c (do_test): New file.
2019-06-17 Rafal Luzynski <digitalfreak@lingonborough.com>
[BZ #24614]

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@ -310,7 +310,7 @@ test-xfail-tst-protected1b = yes
endif
ifeq (yesyes,$(have-fpie)$(build-shared))
modules-names += tst-piemod1
tests += tst-pie1 tst-pie2
tests += tst-pie1 tst-pie2 tst-dlopen-pie
tests-pie += tst-pie1 tst-pie2
ifeq (yes,$(have-protected-data))
tests += vismain
@ -1084,6 +1084,8 @@ CFLAGS-tst-pie2.c += $(pie-ccflag)
$(objpfx)tst-piemod1.so: $(libsupport)
$(objpfx)tst-pie1: $(objpfx)tst-piemod1.so
$(objpfx)tst-dlopen-pie: $(libdl)
$(objpfx)tst-dlopen-pie.out: $(objpfx)tst-pie1
ifeq (yes,$(build-shared))
# NB: Please keep cet-built-dso in sysdeps/x86/Makefile in sync with

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@ -1158,6 +1158,10 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
goto call_lose;
}
/* dlopen of an executable is not valid because it is not possible
to perform proper relocations, handle static TLS, or run the
ELF constructors. For PIE, the check needs the dynamic
section, so there is another check below. */
if (__glibc_unlikely (type != ET_DYN)
&& __glibc_unlikely ((mode & __RTLD_OPENEXEC) == 0))
{
@ -1194,9 +1198,11 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
elf_get_dynamic_info (l, NULL);
/* Make sure we are not dlopen'ing an object that has the
DF_1_NOOPEN flag set. */
if (__glibc_unlikely (l->l_flags_1 & DF_1_NOOPEN)
&& (mode & __RTLD_DLOPEN))
DF_1_NOOPEN flag set, or a PIE object. */
if ((__glibc_unlikely (l->l_flags_1 & DF_1_NOOPEN)
&& (mode & __RTLD_DLOPEN))
|| (__glibc_unlikely (l->l_flags_1 & DF_1_PIE)
&& __glibc_unlikely ((mode & __RTLD_OPENEXEC) == 0)))
{
/* We are not supposed to load this object. Free all resources. */
_dl_unmap_segments (l);
@ -1207,7 +1213,11 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
if (l->l_phdr_allocated)
free ((void *) l->l_phdr);
errstring = N_("shared object cannot be dlopen()ed");
if (l->l_flags_1 & DF_1_PIE)
errstring
= N_("cannot dynamically load position-independent executable");
else
errstring = N_("shared object cannot be dlopen()ed");
goto call_lose;
}

49
elf/tst-dlopen-pie.c Normal file
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@ -0,0 +1,49 @@
/* dlopen test for PIE objects.
Copyright (C) 2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
/* This test attempts to open the (otherwise unrelated) PIE test
program elf/tst-pie1 and expects the attempt to fail. */
#include <dlfcn.h>
#include <stddef.h>
#include <string.h>
#include <support/check.h>
#include <support/support.h>
static void
test_mode (int mode)
{
char *pie_path = xasprintf ("%s/elf/tst-pie1", support_objdir_root);
if (dlopen (pie_path, mode) != NULL)
FAIL_EXIT1 ("dlopen succeeded unexpectedly (%d)", mode);
const char *message = dlerror ();
const char *expected
= "cannot dynamically load position-independent executable";
if (strstr (message, expected) == NULL)
FAIL_EXIT1 ("unexpected error message (mode %d): %s", mode, message);
}
static int
do_test (void)
{
test_mode (RTLD_LAZY);
test_mode (RTLD_NOW);
return 0;
}
#include <support/test-driver.c>

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@ -23,7 +23,7 @@
# endif
# define DT_1_SUPPORTED_MASK \
(DF_1_NOW | DF_1_NODELETE | DF_1_INITFIRST | DF_1_NOOPEN \
| DF_1_ORIGIN | DF_1_NODEFLIB)
| DF_1_ORIGIN | DF_1_NODEFLIB | DF_1_PIE)
#endif /* !_ISOMAC */
#endif /* elf.h */