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

diff --git a/ChangeLog b/ChangeLog
index f8d28b4..664928d 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2018-06-26  Florian Weimer  <fweimer@redhat.com>
+
+       [BZ #23313]
+       * libio/vtables.c (check_stdfiles_vtables): New ELF constructor.
+
 2018-06-25  Florian Weimer  <fweimer@redhat.com>
 
        [BZ #18023]

diff --git a/libio/vtables.c b/libio/vtables.c
index 9fd4ccf..9df7566 100644 (file)
--- a/libio/vtables.c
+++ b/libio/vtables.c
@@ -71,3 +71,19 @@ _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