commit f42373f911a28d34325a5bfc1ed5a962c89da7eb
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Thu Sep 16 08:15:29 2021 -0700
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>
(cherry picked from commit b413280cfb16834450f66f554bc0d618bb513851)
diff --git a/elf/Makefile b/elf/Makefile
index d05f410592723f09..de854b4d1a815bd3 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -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 \
@@ -357,7 +357,7 @@ 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.
@@ -1906,3 +1906,10 @@ $(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
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 650e4edc35e5e582..4445c28ef3fb4a7e 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -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. */
diff --git a/elf/dl-reloc-static-pie.c b/elf/dl-reloc-static-pie.c
index d5bd2f31e9ca50ce..2fb02d727654c87d 100644
--- a/elf/dl-reloc-static-pie.c
+++ b/elf/dl-reloc-static-pie.c
@@ -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);
diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
index d8ec32377d37635c..4aa2058abf6443c9 100644
--- a/elf/get-dynamic-info.h
+++ b/elf/get-dynamic-info.h
@@ -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
diff --git a/elf/rtld.c b/elf/rtld.c
index 08cf50145a1c01ce..405166d62b34847c 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -464,6 +464,7 @@ _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;
@@ -547,7 +548,7 @@ _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;
@@ -1469,6 +1470,7 @@ 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
@@ -1614,7 +1616,7 @@ 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
diff --git a/elf/setup-vdso.h b/elf/setup-vdso.h
index 86c491e49c98345d..f44748bc9858e5fd 100644
--- a/elf/setup-vdso.h
+++ b/elf/setup-vdso.h
@@ -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;
diff --git a/elf/tst-ro-dynamic-mod.c b/elf/tst-ro-dynamic-mod.c
new file mode 100644
index 0000000000000000..6d99925964c50caf
--- /dev/null
+++ b/elf/tst-ro-dynamic-mod.c
@@ -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;
diff --git a/elf/tst-ro-dynamic-mod.map b/elf/tst-ro-dynamic-mod.map
new file mode 100644
index 0000000000000000..2fe4a2998cddd587
--- /dev/null
+++ b/elf/tst-ro-dynamic-mod.map
@@ -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);
+}
diff --git a/elf/tst-ro-dynamic.c b/elf/tst-ro-dynamic.c
new file mode 100644
index 0000000000000000..3a18f8789ad386bb
--- /dev/null
+++ b/elf/tst-ro-dynamic.c
@@ -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>
diff --git a/include/link.h b/include/link.h
index 4af16cb59639a077..c46aced9f7b43ba0 100644
--- a/include/link.h
+++ b/include/link.h
@@ -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
diff --git a/sysdeps/generic/dl-relocate-ld.h b/sysdeps/generic/dl-relocate-ld.h
new file mode 100644
index 0000000000000000..5fae206db9941e97
--- /dev/null
+++ b/sysdeps/generic/dl-relocate-ld.h
@@ -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 */
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 1ceb9c3212c148ba..ed10953f34b96c49 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -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;
diff --git a/sysdeps/mips/dl-relocate-ld.h b/sysdeps/mips/dl-relocate-ld.h
new file mode 100644
index 0000000000000000..0c18d9a567cad54f
--- /dev/null
+++ b/sysdeps/mips/dl-relocate-ld.h
@@ -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 */
diff --git a/sysdeps/mips/ldsodefs.h b/sysdeps/mips/ldsodefs.h
index 4db7c60e38e42ef2..36fd09a8bdb4cacf 100644
--- a/sysdeps/mips/ldsodefs.h
+++ b/sysdeps/mips/ldsodefs.h
@@ -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
diff --git a/sysdeps/riscv/dl-relocate-ld.h b/sysdeps/riscv/dl-relocate-ld.h
new file mode 100644
index 0000000000000000..10327454b17a7097
--- /dev/null
+++ b/sysdeps/riscv/dl-relocate-ld.h
@@ -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 */
diff --git a/sysdeps/riscv/ldsodefs.h b/sysdeps/riscv/ldsodefs.h
index 0c696714a7a93cff..8947ffe4b5026a2e 100644
--- a/sysdeps/riscv/ldsodefs.h
+++ b/sysdeps/riscv/ldsodefs.h
@@ -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