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-rw-r--r--libio/vtables.c89
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diff --git a/libio/vtables.c b/libio/vtables.c
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+++ b/libio/vtables.c
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+/* libio vtable validation.
+ Copyright (C) 2016-2018 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
+ <http://www.gnu.org/licenses/>. */
+
+#include <dlfcn.h>
+#include <libioP.h>
+#include <stdio.h>
+#include <ldsodefs.h>
+
+#ifdef SHARED
+
+void (*IO_accept_foreign_vtables) (void) attribute_hidden;
+
+/* Used to detected multiple libcs. */
+extern struct dl_open_hook *_dl_open_hook;
+libc_hidden_proto (_dl_open_hook);
+
+#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);
+#ifdef PTR_DEMANGLE
+ PTR_DEMANGLE (flag);
+#endif
+ 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