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elf: Assign TLS modid later during dlopen [BZ #24930]

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Commit a42faf59d6 ("Fix BZ #16634.")
attempted to fix a TLS modid consistency issue by adding additional
checks to the open_verify function.  However, this is fragile
because open_verify cannot reliably predict whether
_dl_map_object_from_fd will later fail in the more complex cases
(such as memory allocation failures).  Therefore, this commit
assigns the TLS modid as late as possible.  At that point, the link
map pointer will eventually be passed to _dl_close, which will undo
the TLS modid assignment.

Reviewed-by: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>
This commit is contained in:
Florian Weimer 2019-10-04 21:23:51 +02:00
parent 2b26b084e4
commit 77523d5e43
4 changed files with 60 additions and 30 deletions
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12
ChangeLog
View File

@ -1,3 +1,15 @@
2019-10-04 Florian Weimer <fweimer@redhat.com>
[BZ #24930]
* elf/dl-load.c (_dl_map_object_from_fd): Only assign TLS modid if
the link map will be returned to the caller.
* elf/Makefile [$(have-fpie) && $(build-shared)] (tests, tests-pie):
Add tst-dlopen-aout-pie.
(tst-tst-dlopen-aout-no-pie): Set.
(CFLAGS-tst-dlopen-aout-pie.c): Build with -fpie.
(tst-dlopen-aout-pie): Link with -ldl -lpthread.
* elf/tst-dlopen-aout-pie.c: New file.
2019-10-04 Florian Weimer <fweimer@redhat.com>
[BZ #24900]

8
elf/Makefile
View File

@ -308,8 +308,8 @@ test-xfail-tst-protected1b = yes
endif
ifeq (yesyes,$(have-fpie)$(build-shared))
modules-names += tst-piemod1
tests += tst-pie1 tst-pie2 tst-dlopen-pie
tests-pie += tst-pie1 tst-pie2
tests += tst-pie1 tst-pie2 tst-dlopen-pie tst-dlopen-aout-pie
tests-pie += tst-pie1 tst-pie2 tst-dlopen-aout-pie
ifeq (yes,$(have-protected-data))
tests += vismain
tests-pie += vismain
@ -1267,7 +1267,11 @@ tst-leaks1-static-ENV = MALLOC_TRACE=$(objpfx)tst-leaks1-static.mtrace
$(objpfx)tst-addr1: $(libdl)
$(objpfx)tst-thrlock: $(libdl) $(shared-thread-library)
tst-tst-dlopen-aout-no-pie = yes
$(objpfx)tst-dlopen-aout: $(libdl) $(shared-thread-library)
CFLAGS-tst-dlopen-aout-pie.c += $(pie-ccflag)
$(objpfx)tst-dlopen-aout-pie: $(libdl) $(shared-thread-library)
$(objpfx)tst-dlopen-aout-container: $(libdl) $(shared-thread-library)
LDFLAGS-tst-dlopen-aout-container += -Wl,-rpath,\$$ORIGIN

43
elf/dl-load.c
View File

@ -1118,27 +1118,21 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
offset. We will adjust it later. */
l->l_tls_initimage = (void *) ph->p_vaddr;
/* If not loading the initial set of shared libraries,
check whether we should permit loading a TLS segment. */
if (__glibc_likely (l->l_type == lt_library)
/* If GL(dl_tls_dtv_slotinfo_list) == NULL, then rtld.c did
not set up TLS data structures, so don't use them now. */
|| __glibc_likely (GL(dl_tls_dtv_slotinfo_list) != NULL))
{
/* Assign the next available module ID. */
l->l_tls_modid = _dl_next_tls_modid ();
break;
}
/* l->l_tls_modid is assigned below, once there is no
possibility for failure. */
if (l->l_type != lt_library
&& GL(dl_tls_dtv_slotinfo_list) == NULL)
{
#ifdef SHARED
/* We are loading the executable itself when the dynamic
linker was executed directly. The setup will happen
later. Otherwise, the TLS data structures are already
initialized, and we assigned a TLS modid above. */
later. */
assert (l->l_prev == NULL || (mode & __RTLD_AUDIT) != 0);
#else
assert (false && "TLS not initialized in static application");
#endif
}
break;
case PT_GNU_STACK:
@ -1379,6 +1373,18 @@ cannot enable executable stack as shared object requires");
add_name_to_object (l, ((const char *) D_PTR (l, l_info[DT_STRTAB])
+ l->l_info[DT_SONAME]->d_un.d_val));
/* _dl_close can only eventually undo the module ID assignment (via
remove_slotinfo) if this function returns a pointer to a link
map. Therefore, delay this step until all possibilities for
failure have been excluded. */
if (l->l_tls_blocksize > 0
&& (__glibc_likely (l->l_type == lt_library)
/* If GL(dl_tls_dtv_slotinfo_list) == NULL, then rtld.c did
not set up TLS data structures, so don't use them now. */
|| __glibc_likely (GL(dl_tls_dtv_slotinfo_list) != NULL)))
/* Assign the next available module ID. */
l->l_tls_modid = _dl_next_tls_modid ();
#ifdef DL_AFTER_LOAD
DL_AFTER_LOAD (l);
#endif
@ -1646,17 +1652,6 @@ open_verify (const char *name, int fd,
errstring = N_("only ET_DYN and ET_EXEC can be loaded");
goto call_lose;
}
else if (__glibc_unlikely (ehdr->e_type == ET_EXEC
&& (mode & __RTLD_OPENEXEC) == 0))
{
/* BZ #16634. It is an error to dlopen ET_EXEC (unless
__RTLD_OPENEXEC is explicitly set). We return error here
so that code in _dl_map_object_from_fd does not try to set
l_tls_modid for this module. */
errstring = N_("cannot dynamically load executable");
goto call_lose;
}
else if (__glibc_unlikely (ehdr->e_phentsize != sizeof (ElfW(Phdr))))
{
errstring = N_("ELF file's phentsize not the expected size");

19
elf/tst-dlopen-aout-pie.c Normal file
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@ -0,0 +1,19 @@
/* Test case for BZ #16634 and BZ#24900. PIE version.
Copyright (C) 2014-2019 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/>. */
#include "tst-dlopen-aout.c"