commit 3bb748257405e94e13de76573a4e9da1cfd961d0

Author: Florian Weimer <fweimer@redhat.com>

Date:   Tue Jul 3 15:54:49 2018 +0200

    libio: Disable vtable validation in case of interposition [BZ #23313]

    (cherry picked from commit c402355dfa7807b8e0adb27c009135a7e2b9f1b0)

Backported from the upstream release/2.26/master branch.

diff --git a/libio/vtables.c b/libio/vtables.c

index e364ea03edbfa75b..d6478e4bab9050ce 100644

--- a/libio/vtables.c

+++ b/libio/vtables.c

@@ -68,3 +68,19 @@ _IO_vtable_check (void)

   __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