libio: Disable vtable validation in case of interposition [BZ #23313]
Commit Message
On 06/22/2018 12:51 PM, Florian Weimer wrote:
> Right. I don't think we need to support static linking for backwards
> compatibility with these old libraries, so I'll “#ifndef SHARED” around
> the constructor.
Here's what I've committed.
Thanks,
Florian
Subject: [PATCH COMMITTED] libio: Disable vtable validation in case of interposition [BZ #23313]
To: libc-alpha@sourceware.org
2018-06-26 Florian Weimer <fweimer@redhat.com>
[BZ #23313]
* libio/vtables.c (check_stdfiles_vtables): New ELF constructor.
@@ -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