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/* libio vtable validation.
Copyright (C) 2016-2022 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 <dlfcn.h>
#include <libioP.h>
#include <stdio.h>
#include <ldsodefs.h>
#include <pointer_guard.h>
#ifdef SHARED
void (*IO_accept_foreign_vtables) (void) attribute_hidden;
#else /* !SHARED */
/* Used to check whether static dlopen support is needed. */
# pragma weak __dlopen
#endif
void attribute_hidden
_IO_vtable_check (void)
{
#ifdef SHARED
/* Honor the compatibility flag. */
void (*flag) (void) = atomic_load_relaxed (&IO_accept_foreign_vtables);
PTR_DEMANGLE (flag);
if (flag == &_IO_vtable_check)
return;
/* In case this libc copy is in a non-default namespace, we always
need to accept foreign vtables because there is always a
possibility that FILE * objects are passed across the linking
boundary. */
{
Dl_info di;
struct link_map *l;
if (!rtld_active ()
|| (_dl_addr (_IO_vtable_check, &di, &l, NULL) != 0
&& l->l_ns != LM_ID_BASE))
return;
}
#else /* !SHARED */
/* We cannot perform vtable validation in the static dlopen case
because FILE * handles might be passed back and forth across the
boundary. Therefore, we disable checking in this case. */
if (__dlopen != NULL)
return;
#endif
__libc_fatal ("Fatal error: glibc detected an invalid stdio handle\n");
}
/* Some variants of libstdc++ interpose _IO_2_1_stdin_ etc. and
install their own vtables directly, without calling _IO_init or
other functions. Detect this by looking at the vtables values
during startup, and disable vtable validation in this case. */
#ifdef SHARED
__attribute__ ((constructor))
static void
check_stdfiles_vtables (void)
{
if (_IO_2_1_stdin_.vtable != &_IO_file_jumps
|| _IO_2_1_stdout_.vtable != &_IO_file_jumps
|| _IO_2_1_stderr_.vtable != &_IO_file_jumps)
IO_set_accept_foreign_vtables (&_IO_vtable_check);
}
#endif
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