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Add run-time check for indirect external access

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When performing symbol lookup for references in executable without
indirect external access:

1. Disallow copy relocations in executable against protected data symbols
in a shared object with indirect external access.
2. Disallow non-zero symbol values of undefined function symbols in
executable, which are used as the function pointer, against protected
function symbols in a shared object with indirect external access.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
H.J. Lu 2021-06-18 16:50:39 -07:00
parent 1bd888d0b7
commit 349b0441da
2 changed files with 59 additions and 0 deletions
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5
elf/dl-lookup.c
View File

@ -24,6 +24,7 @@
#include <ldsodefs.h> #include <ldsodefs.h>
#include <dl-hash.h> #include <dl-hash.h>
#include <dl-machine.h> #include <dl-machine.h>
#include <dl-protected.h>
#include <sysdep-cancel.h> #include <sysdep-cancel.h>
#include <libc-lock.h> #include <libc-lock.h>
#include <tls.h> #include <tls.h>
@ -527,6 +528,10 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
if (__glibc_unlikely (dl_symbol_visibility_binds_local_p (sym))) if (__glibc_unlikely (dl_symbol_visibility_binds_local_p (sym)))
goto skip; goto skip;
if (ELFW(ST_VISIBILITY) (sym->st_other) == STV_PROTECTED)
_dl_check_protected_symbol (undef_name, undef_map, ref, map,
type_class);
switch (ELFW(ST_BIND) (sym->st_info)) switch (ELFW(ST_BIND) (sym->st_info))
{ {
case STB_WEAK: case STB_WEAK:

54
sysdeps/generic/dl-protected.h Normal file
View File

@ -0,0 +1,54 @@
/* Support for STV_PROTECTED visibility. 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_PROTECTED_H
#define _DL_PROTECTED_H
static inline void __attribute__ ((always_inline))
_dl_check_protected_symbol (const char *undef_name,
const struct link_map *undef_map,
const ElfW(Sym) *ref,
const struct link_map *map,
int type_class)
{
if (undef_map != NULL
&& undef_map->l_type == lt_executable
&& !(undef_map->l_1_needed
& GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS)
&& (map->l_1_needed
& GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS))
{
if ((type_class & ELF_RTYPE_CLASS_COPY))
/* Disallow copy relocations in executable against protected
data symbols in a shared object which needs indirect external
access. */
_dl_signal_error (0, map->l_name, undef_name,
N_("copy relocation against non-copyable protected symbol"));
else if (ref->st_value != 0
&& ref->st_shndx == SHN_UNDEF
&& (type_class & ELF_RTYPE_CLASS_PLT))
/* Disallow non-zero symbol values of undefined symbols in
executable, which are used as the function pointer, against
protected function symbols in a shared object with indirect
external access. */
_dl_signal_error (0, map->l_name, undef_name,
N_("non-canonical reference to canonical protected function"));
}
}
#endif /* _DL_PROTECTED_H */