From: Florian Weimer <fweimer@redhat.com>
Date: Tue, 26 Jun 2018 08:24:52 +0000 (+0200)
Subject: libio: Disable vtable validation in case of interposition [BZ #23313]
X-Git-Tag: glibc-2.28~161
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c402355dfa7807b8e0adb27c009135a7e2b9f1b0;p=thirdparty%2Fglibc.git

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

diff --git a/ChangeLog b/ChangeLog
index f8d28b496ec..664928d5fe7 100644
--- 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 9fd4ccf642a..9df75668c8a 100644
--- 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