libio/vtables.c

   1 /* libio vtable validation.
   2    Copyright (C) 2016 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <dlfcn.h>
  20 #include <libioP.h>
  21 #include <stdio.h>
  22
  23 #ifdef SHARED
  24
  25 void (*IO_accept_foreign_vtables) (void) attribute_hidden;
  26
  27 /* Used to detected multiple libcs.  */
  28 extern struct dl_open_hook *_dl_open_hook;
  29 libc_hidden_proto (_dl_open_hook);
  30
  31 #else  /* !SHARED */
  32
  33 /* Used to check whether static dlopen support is needed.  */
  34 # pragma weak __dlopen
  35
  36 #endif
  37
  38 void attribute_hidden
  39 _IO_vtable_check (void)
  40 {
  41 #ifdef SHARED
  42   /* Honor the compatibility flag.  */
  43   void (*flag) (void) = atomic_load_relaxed (&IO_accept_foreign_vtables);
  44   PTR_DEMANGLE (flag);
  45   if (flag == &_IO_vtable_check)
  46     return;
  47
  48   /* In case this libc copy is in a non-default namespace, we always
  49      need to accept foreign vtables because there is always a
  50      possibility that FILE * objects are passed across the linking
  51      boundary.  */
  52   {
  53     Dl_info di;
  54     struct link_map *l;
  55     if (_dl_open_hook != NULL
  56         || (_dl_addr (_IO_vtable_check, &di, &l, NULL) != 0
  57             && l->l_ns != LM_ID_BASE))
  58       return;
  59   }
  60
  61 #else /* !SHARED */
  62   /* We cannot perform vtable validation in the static dlopen case
  63      because FILE * handles might be passed back and forth across the
  64      boundary.  Therefore, we disable checking in this case.  */
  65   if (__dlopen != NULL)
  66     return;
  67 #endif
  68
  69   __libc_fatal ("Fatal error: glibc detected an invalid stdio handle\n");
  70 }