1/* libio vtable validation.
2 Copyright (C) 2016-2020 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 <https://www.gnu.org/licenses/>. */
18
19#include <dlfcn.h>
20#include <libioP.h>
21#include <stdio.h>
22#include <ldsodefs.h>
23
24#ifdef SHARED
25
26void (*IO_accept_foreign_vtables) (void) attribute_hidden;
27
28/* Used to detected multiple libcs. */
29extern struct dl_open_hook *_dl_open_hook;
30libc_hidden_proto (_dl_open_hook);
31
32#else /* !SHARED */
33
34/* Used to check whether static dlopen support is needed. */
35# pragma weak __dlopen
36
37#endif
38
39void attribute_hidden
40_IO_vtable_check (void)
41{
42#ifdef SHARED
43 /* Honor the compatibility flag. */
44 void (*flag) (void) = atomic_load_relaxed (&IO_accept_foreign_vtables);
45#ifdef PTR_DEMANGLE
46 PTR_DEMANGLE (flag);
47#endif
48 if (flag == &_IO_vtable_check)
49 return;
50
51 /* In case this libc copy is in a non-default namespace, we always
52 need to accept foreign vtables because there is always a
53 possibility that FILE * objects are passed across the linking
54 boundary. */
55 {
56 Dl_info di;
57 struct link_map *l;
58 if (!rtld_active ()
59 || (_dl_addr (_IO_vtable_check, &di, &l, NULL) != 0
60 && l->l_ns != LM_ID_BASE))
61 return;
62 }
63
64#else /* !SHARED */
65 /* We cannot perform vtable validation in the static dlopen case
66 because FILE * handles might be passed back and forth across the
67 boundary. Therefore, we disable checking in this case. */
68 if (__dlopen != NULL)
69 return;
70#endif
71
72 __libc_fatal ("Fatal error: glibc detected an invalid stdio handle\n");
73}
74
75/* Some variants of libstdc++ interpose _IO_2_1_stdin_ etc. and
76 install their own vtables directly, without calling _IO_init or
77 other functions. Detect this by looking at the vtables values
78 during startup, and disable vtable validation in this case. */
79#ifdef SHARED
80__attribute__ ((constructor))
81static void
82check_stdfiles_vtables (void)
83{
84 if (_IO_2_1_stdin_.vtable != &_IO_file_jumps
85 || _IO_2_1_stdout_.vtable != &_IO_file_jumps
86 || _IO_2_1_stderr_.vtable != &_IO_file_jumps)
87 IO_set_accept_foreign_vtables (&_IO_vtable_check);
88}
89#endif
90