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ld.so: Replace DL_RO_DYN_SECTION with dl_relocate_ld [BZ #28340] 

We can't relocate entries in dynamic section if it is readonly:

1. Add a l_ld_readonly field to struct link_map to indicate if dynamic
section is readonly and set it based on p_flags of PT_DYNAMIC segment.
2. Replace DL_RO_DYN_SECTION with dl_relocate_ld to decide if dynamic
section should be relocated.
3. Remove DL_RO_DYN_TEMP_CNT.
4. Don't use a static dynamic section to make readonly dynamic section
in vDSO writable.
5. Remove the temp argument from elf_get_dynamic_info.

This fixes BZ #28340.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
This commit is contained in:
H.J. Lu 2021-09-16 08:15:29 -07:00
parent 4eff749e8f
commit b413280cfb
16 changed files with 198 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
elf/Makefile
View File

@ -224,7 +224,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
tst-tls-ie tst-tls-ie-dlmopen argv0test \
tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
tst-tls20 tst-tls21 tst-dlmopen-dlerror tst-dlmopen-gethostbyname \
tst-dl-is_dso
tst-dl-is_dso tst-ro-dynamic
# reldep9
tests-internal += loadtest unload unload2 circleload1 \
neededtest neededtest2 neededtest3 neededtest4 \
@ -360,7 +360,7 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
libmarkermod4-1 libmarkermod4-2 libmarkermod4-3 libmarkermod4-4 \
tst-tls20mod-bad tst-tls21mod tst-dlmopen-dlerror-mod \
tst-auxvalmod \
tst-dlmopen-gethostbyname-mod \
tst-dlmopen-gethostbyname-mod tst-ro-dynamic-mod \
# Most modules build with _ISOMAC defined, but those filtered out
# depend on internal headers.
@ -1911,3 +1911,10 @@ $(objpfx)tst-getauxval-static.out: $(objpfx)tst-auxvalmod.so
tst-getauxval-static-ENV = LD_LIBRARY_PATH=$(objpfx):$(common-objpfx)
$(objpfx)tst-dlmopen-gethostbyname.out: $(objpfx)tst-dlmopen-gethostbyname-mod.so
$(objpfx)tst-ro-dynamic: $(objpfx)tst-ro-dynamic-mod.so
$(objpfx)tst-ro-dynamic-mod.so: $(objpfx)tst-ro-dynamic-mod.os \
tst-ro-dynamic-mod.map
$(LINK.o) -nostdlib -nostartfiles -shared -o $@ \
-Wl,--script=tst-ro-dynamic-mod.map \
$(objpfx)tst-ro-dynamic-mod.os

3
elf/dl-load.c
View File

@ -1149,6 +1149,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
such a segment to avoid a crash later. */
l->l_ld = (void *) ph->p_vaddr;
l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn));
l->l_ld_readonly = (ph->p_flags & PF_W) == 0;
}
break;
@ -1292,7 +1293,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
else
l->l_ld = (ElfW(Dyn) *) ((ElfW(Addr)) l->l_ld + l->l_addr);
elf_get_dynamic_info (l, NULL);
elf_get_dynamic_info (l);
/* Make sure we are not dlopen'ing an object that has the
DF_1_NOOPEN flag set, or a PIE object. */

12
elf/dl-reloc-static-pie.c
View File

@ -40,7 +40,17 @@ _dl_relocate_static_pie (void)
/* Read our own dynamic section and fill in the info array. */
main_map->l_ld = ((void *) main_map->l_addr + elf_machine_dynamic ());
elf_get_dynamic_info (main_map, NULL);
const ElfW(Phdr) *ph, *phdr = GL(dl_phdr);
size_t phnum = GL(dl_phnum);
for (ph = phdr; ph < &phdr[phnum]; ++ph)
if (ph->p_type == PT_DYNAMIC)
{
main_map->l_ld_readonly = (ph->p_flags & PF_W) == 0;
break;
}
elf_get_dynamic_info (main_map);
# ifdef ELF_MACHINE_BEFORE_RTLD_RELOC
ELF_MACHINE_BEFORE_RTLD_RELOC (main_map->l_info);

21
elf/get-dynamic-info.h
View File

@ -28,7 +28,7 @@ static
auto
#endif
inline void __attribute__ ((unused, always_inline))
elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
elf_get_dynamic_info (struct link_map *l)
{
#if __ELF_NATIVE_CLASS == 32
typedef Elf32_Word d_tag_utype;
@ -69,28 +69,15 @@ elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
info[i] = dyn;
}
#define DL_RO_DYN_TEMP_CNT 8
#ifndef DL_RO_DYN_SECTION
/* Don't adjust .dynamic unnecessarily. */
if (l->l_addr != 0)
if (l->l_addr != 0 && dl_relocate_ld (l))
{
ElfW(Addr) l_addr = l->l_addr;
int cnt = 0;
# define ADJUST_DYN_INFO(tag) \
do \
if (info[tag] != NULL) \
{ \
if (temp) \
{ \
temp[cnt].d_tag = info[tag]->d_tag; \
temp[cnt].d_un.d_ptr = info[tag]->d_un.d_ptr + l_addr; \
info[tag] = temp + cnt++; \
} \
else \
info[tag]->d_un.d_ptr += l_addr; \
} \
info[tag]->d_un.d_ptr += l_addr; \
while (0)
ADJUST_DYN_INFO (DT_HASH);
@ -107,9 +94,7 @@ elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
# undef ADJUST_DYN_INFO
assert (cnt <= DL_RO_DYN_TEMP_CNT);
}
#endif
if (info[DT_PLTREL] != NULL)
{
#if ELF_MACHINE_NO_RELA

6
elf/rtld.c
View File

@ -463,6 +463,7 @@ _dl_start_final (void *arg, struct dl_start_final_info *info)
#ifndef DONT_USE_BOOTSTRAP_MAP
GL(dl_rtld_map).l_addr = info->l.l_addr;
GL(dl_rtld_map).l_ld = info->l.l_ld;
GL(dl_rtld_map).l_ld_readonly = info->l.l_ld_readonly;
memcpy (GL(dl_rtld_map).l_info, info->l.l_info,
sizeof GL(dl_rtld_map).l_info);
GL(dl_rtld_map).l_mach = info->l.l_mach;
@ -546,7 +547,7 @@ _dl_start (void *arg)
/* Read our own dynamic section and fill in the info array. */
bootstrap_map.l_ld = (void *) bootstrap_map.l_addr + elf_machine_dynamic ();
elf_get_dynamic_info (&bootstrap_map, NULL);
elf_get_dynamic_info (&bootstrap_map);
#if NO_TLS_OFFSET != 0
bootstrap_map.l_tls_offset = NO_TLS_OFFSET;
@ -1468,6 +1469,7 @@ dl_main (const ElfW(Phdr) *phdr,
/* This tells us where to find the dynamic section,
which tells us everything we need to do. */
main_map->l_ld = (void *) main_map->l_addr + ph->p_vaddr;
main_map->l_ld_readonly = (ph->p_flags & PF_W) == 0;
break;
case PT_INTERP:
/* This "interpreter segment" was used by the program loader to
@ -1613,7 +1615,7 @@ dl_main (const ElfW(Phdr) *phdr,
if (! rtld_is_main)
{
/* Extract the contents of the dynamic section for easy access. */
elf_get_dynamic_info (main_map, NULL);
elf_get_dynamic_info (main_map);
/* If the main map is libc.so, update the base namespace to
refer to this map. If libc.so is loaded later, this happens

5
elf/setup-vdso.h
View File

@ -33,8 +33,6 @@ setup_vdso (struct link_map *main_map __attribute__ ((unused)),
0, LM_ID_BASE);
if (__glibc_likely (l != NULL))
{
static ElfW(Dyn) dyn_temp[DL_RO_DYN_TEMP_CNT] attribute_relro;
l->l_phdr = ((const void *) GLRO(dl_sysinfo_dso)
+ GLRO(dl_sysinfo_dso)->e_phoff);
l->l_phnum = GLRO(dl_sysinfo_dso)->e_phnum;
@ -45,6 +43,7 @@ setup_vdso (struct link_map *main_map __attribute__ ((unused)),
{
l->l_ld = (void *) ph->p_vaddr;
l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn));
l->l_ld_readonly = (ph->p_flags & PF_W) == 0;
}
else if (ph->p_type == PT_LOAD)
{
@ -65,7 +64,7 @@ setup_vdso (struct link_map *main_map __attribute__ ((unused)),
l->l_map_end += l->l_addr;
l->l_text_end += l->l_addr;
l->l_ld = (void *) ((ElfW(Addr)) l->l_ld + l->l_addr);
elf_get_dynamic_info (l, dyn_temp);
elf_get_dynamic_info (l);
_dl_setup_hash (l);
l->l_relocated = 1;

19
elf/tst-ro-dynamic-mod.c Normal file
View File

@ -0,0 +1,19 @@
/* Test case for DSO with readonly dynamic section.
Copyright (C) 2021 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
<https://www.gnu.org/licenses/>. */
int foo = -1;

16
elf/tst-ro-dynamic-mod.map Normal file
View File

@ -0,0 +1,16 @@
SECTIONS
{
. = SIZEOF_HEADERS;
.dynamic : { *(.dynamic) } :text :dynamic
.rodata : { *(.data*) *(.bss*) } :text
/DISCARD/ : {
*(.note.gnu.property)
}
.note : { *(.note.*) } :text :note
}
PHDRS
{
text PT_LOAD FLAGS(5) FILEHDR PHDRS;
dynamic PT_DYNAMIC FLAGS(4);
note PT_NOTE FLAGS(4);
}

31
elf/tst-ro-dynamic.c Normal file
View File

@ -0,0 +1,31 @@
/* Test case for DSO with readonly dynamic section.
Copyright (C) 2021 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
<https://www.gnu.org/licenses/>. */
#include <support/check.h>
#include <support/test-driver.h>
extern int foo;
static int
do_test (void)
{
TEST_COMPARE (foo, -1);
return 0;
}
#include <support/test-driver.c>

3
include/link.h
View File

@ -205,6 +205,7 @@ struct link_map
unsigned int l_free_initfini:1; /* Nonzero if l_initfini can be
freed, ie. not allocated with
the dummy malloc in ld.so. */
unsigned int l_ld_readonly:1; /* Nonzero if dynamic section is readonly. */
/* NODELETE status of the map. Only valid for maps of type
lt_loaded. Lazy binding sets l_nodelete_active directly,
@ -342,6 +343,8 @@ struct link_map
unsigned long long int l_serial;
};
#include <dl-relocate-ld.h>
/* Information used by audit modules. For most link maps, this data
immediate follows the link map in memory. For the dynamic linker,
it is allocated separately. See link_map_audit_state in

32
sysdeps/generic/dl-relocate-ld.h Normal file
View File

@ -0,0 +1,32 @@
/* Check if dynamic section should be relocated. Generic version.
Copyright (C) 2021 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_RELOCATE_LD_H
#define _DL_RELOCATE_LD_H
/* Return true if dynamic section in the shared library L should be
relocated. */
static inline bool
dl_relocate_ld (const struct link_map *l)
{
/* Don't relocate dynamic section if it is readonly */
return !l->l_ld_readonly;
}
#endif /* _DL_RELOCATE_LD_H */

7
sysdeps/generic/ldsodefs.h
View File

@ -75,11 +75,8 @@ __BEGIN_DECLS
have to be accessed via the D_PTR macro. The macro is needed since for
most architectures the entry is already relocated - but for some not
and we need to relocate at access time. */
#ifdef DL_RO_DYN_SECTION
# define D_PTR(map, i) ((map)->i->d_un.d_ptr + (map)->l_addr)
#else
# define D_PTR(map, i) (map)->i->d_un.d_ptr
#endif
#define D_PTR(map, i) \
((map)->i->d_un.d_ptr + (dl_relocate_ld (map) ? 0 : (map)->l_addr))
/* Result of the lookup functions and how to retrieve the base address. */
typedef struct link_map *lookup_t;

32
sysdeps/mips/dl-relocate-ld.h Normal file
View File

@ -0,0 +1,32 @@
/* Check if dynamic section should be relocated. MIPS version.
Copyright (C) 2021 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_RELOCATE_LD_H
#define _DL_RELOCATE_LD_H
/* Return true if dynamic section in the shared library L should be
relocated. */
static inline bool
dl_relocate_ld (const struct link_map *l)
{
/* Never relocate dynamic section. */
return false;
}
#endif /* _DL_RELOCATE_LD_H */

4
sysdeps/mips/ldsodefs.h
View File

@ -75,10 +75,6 @@ struct La_mips_64_retval;
struct La_mips_64_retval *, \
const char *);
/* The MIPS ABI specifies that the dynamic section has to be read-only. */
#define DL_RO_DYN_SECTION 1
#include_next <ldsodefs.h>
/* The 64-bit MIPS ELF ABI uses an unusual reloc format. Each

32
sysdeps/riscv/dl-relocate-ld.h Normal file
View File

@ -0,0 +1,32 @@
/* Check if dynamic section should be relocated. RISC-V version.
Copyright (C) 2021 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_RELOCATE_LD_H
#define _DL_RELOCATE_LD_H
/* Return true if dynamic section in the shared library L should be
relocated. */
static inline bool
dl_relocate_ld (const struct link_map *l)
{
/* Never relocate dynamic section for ABI compatibility. */
return false;
}
#endif /* _DL_RELOCATE_LD_H */

5
sysdeps/riscv/ldsodefs.h
View File

@ -38,11 +38,6 @@ struct La_riscv_retval;
struct La_riscv_retval *, \
const char *);
/* Although the RISC-V ABI does not specify that the dynamic section has
to be read-only, it needs to be kept for ABI compatibility. */
#define DL_RO_DYN_SECTION 1
#include_next <ldsodefs.h>
#endif