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Skip PT_DYNAMIC segment with p_filesz == 0 [BZ #22101]

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ELF objects generated with "objcopy --only-keep-debug" have

Type     Offset  VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
DYNAMIC  0x0+e28 0x0+200e40 0x0+200e40 0x0+    0x0+1a0 RW  0x8

with 0 file size. ld.so should skip such PT_DYNAMIC segments.

Without a PT_DYNAMIC segment the loading of the shared object will
fail, and therefore ldd on such objects will also fail instead of
crashing. This provides better diagnostics for tooling that is
attempting to inspect the invalid shared objects which may just
contain debug information.

	[BZ #22101]
	* elf/Makefile (tests): Add tst-debug1.
	($(objpfx)tst-debug1): New.
	($(objpfx)tst-debug1.out): Likewise.
	($(objpfx)tst-debug1mod1.so): Likewise.
	* elf/dl-load.c (_dl_map_object_from_fd): Skip PT_DYNAMIC segment
	with p_filesz == 0.
	* elf/tst-debug1.c: New file.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
H.J. Lu 2017-09-26 13:49:48 -07:00
parent 2d9193f2f5
commit 592d5c7539
4 changed files with 61 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
ChangeLog
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@ -1,3 +1,14 @@
2017-09-26 H.J. Lu <hongjiu.lu@intel.com>
[BZ #22101]
* elf/Makefile (tests): Add tst-debug1.
($(objpfx)tst-debug1): New.
($(objpfx)tst-debug1.out): Likewise.
($(objpfx)tst-debug1mod1.so): Likewise.
* elf/dl-load.c (_dl_map_object_from_fd): Skip PT_DYNAMIC segment
with p_filesz == 0.
* elf/tst-debug1.c: New file.
2017-09-26 Joseph Myers <joseph@codesourcery.com>
* sysdeps/sparc/sparc-ifunc.h [!__ASSEMBLER__] (sparc_libm_ifunc):

9
elf/Makefile
View File

@ -181,7 +181,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
tst-initorder tst-initorder2 tst-relsort1 tst-null-argv \
tst-tlsalign tst-tlsalign-extern tst-nodelete-opened \
tst-nodelete2 tst-audit11 tst-audit12 tst-dlsym-error tst-noload \
tst-latepthread tst-tls-manydynamic tst-nodelete-dlclose
tst-latepthread tst-tls-manydynamic tst-nodelete-dlclose \
tst-debug1
# reldep9
tests-internal += loadtest unload unload2 circleload1 \
neededtest neededtest2 neededtest3 neededtest4 \
@ -1417,3 +1418,9 @@ tst-env-setuid-ENV = MALLOC_CHECK_=2 MALLOC_MMAP_THRESHOLD_=4096 \
LD_HWCAP_MASK=0x1
tst-env-setuid-tunables-ENV = \
GLIBC_TUNABLES=glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096
$(objpfx)tst-debug1: $(libdl)
$(objpfx)tst-debug1.out: $(objpfx)tst-debug1mod1.so
$(objpfx)tst-debug1mod1.so: $(objpfx)testobj1.so
$(OBJCOPY) --only-keep-debug $< $@

10
elf/dl-load.c
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@ -1052,8 +1052,14 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
segments are mapped in. We record the addresses it says
verbatim, and later correct for the run-time load address. */
case PT_DYNAMIC:
l->l_ld = (void *) ph->p_vaddr;
l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn));
if (ph->p_filesz)
{
/* Debuginfo only files from "objcopy --only-keep-debug"
contain a PT_DYNAMIC segment with p_filesz == 0. Skip
such a segment to avoid a crash later. */
l->l_ld = (void *) ph->p_vaddr;
l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn));
}
break;
case PT_PHDR:

34
elf/tst-debug1.c Normal file
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@ -0,0 +1,34 @@
/* Unit test for dlopen on ELF object from "objcopy --only-keep-debug".
Copyright (C) 2017 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 <dlfcn.h>
#include <stdio.h>
static int
do_test (void)
{
void *h = dlopen ("tst-debug1mod1.so", RTLD_LAZY);
if (h != NULL)
{
puts ("shouldn't load tst-debug1mod1.so");
return 1;
}
return 0;
}
#include <support/test-driver.c>