From: abudovski@...
Date: 2015-08-01T03:14:33+00:00
Subject: [ruby-core:70209] [Ruby trunk - Bug #11393] segfault on trivial application, embedding in C app.

Issue #11393 has been updated by Alex Budovski.


Thanks!

That didn't AV.

I guess I misunderstood what rb_load_file meant. I couldn't find a definitive reference, and there are no comments in the code.

It seems like rb_require is the correct thing to use to run a script.

I tried making the change (this time to a real file):

~~~
#include <ruby.h>
#include <stdio.h>
#include <assert.h>

static VALUE
load_file(VALUE name)
{
	return (VALUE)rb_require((const char *)name);
}

int main(int argc, char** argv)
{
	int state;
	ruby_setup();
	rb_protect(load_file, (VALUE)"E:\\src\\rb\\a.rb", &state);
	ruby_cleanup(0);
	if (state) {
		fprintf(stderr, "load failed\n");
		return EXIT_FAILURE;
	}
	return EXIT_SUCCESS;
}
~~~

And now it AVs in cleanup:

>	ntdll.dll!RtlpEnterCriticalSectionContended(_RTL_CRITICAL_SECTION * CriticalSection) Line 1052	C
 	x64-msvcr120-ruby220.dll!rb_w32_write(int fd, const void * buf, unsigned __int64 size) Line 6539	C
 	x64-msvcr120-ruby220.dll!io_flush_buffer_sync(void * arg) Line 1013	C
 	x64-msvcr120-ruby220.dll!fptr_finalize(rb_io_t * fptr, int noraise) Line 4253	C
 	x64-msvcr120-ruby220.dll!rb_io_fptr_finalize(rb_io_t * fptr) Line 4353	C
 	x64-msvcr120-ruby220.dll!finalize_list(rb_objspace * objspace, unsigned __int64 zombie) Line 2479	C
 	x64-msvcr120-ruby220.dll!rb_objspace_call_finalizer(rb_objspace * objspace) Line 2630	C
 	x64-msvcr120-ruby220.dll!ruby_cleanup(volatile int ex) Line 232	C
 	rbtest1.exe!main(int argc, char * * argv) Line 19	C++

----------------------------------------
Bug #11393: segfault on trivial application, embedding in C app.
https://bugs.ruby-lang.org/issues/11393#change-53634

* Author: Alex Budovski
* Status: Third Party's Issue
* Priority: Normal
* Assignee: 
* ruby -v: 2.2.2
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
~~~c
#include <ruby.h>
#include <stdio.h>
int main()
{
	ruby_setup();
	rb_load_file("abc");  // AV here
	ruby_cleanup(0);
}
~~~

~~~
  rbtest1.exe!rb_vm_bugreport(const void * ctx) Line 1024 C
  rbtest1.exe!rb_bug_context(const void * ctx, const char * fmt, ...) Line 422 C
  rbtest1.exe!sigsegv(int sig) Line 887 C
  [External Code]
  rbtest1.exe!rb_threadptr_tag_jump(rb_thread_struct * th, int st) Line 163 C
> rbtest1.exe!rb_ensure(unsigned __int64 (...) * b_proc, unsigned __int64 data1, unsigned __int64 (...) * e_proc, unsigned __int64 data2) Line 915 C
  rbtest1.exe!load_file(unsigned __int64 parser, unsigned __int64 fname, int script, cmdline_options * opt) Line 1779 C
  rbtest1.exe!rb_load_file_str(unsigned __int64 fname_v) Line 1794 C
  rbtest1.exe!rb_load_file(const char * fname) Line 1786 C
  rbtest1.exe!main() Line 7 C++
~~~

Tried using both stable 2.2.2 and git master
f965866f4f0a00c8179a1097e89fb4e61f71a92a

Win Server 2012 R2, VS 2013 Update 4. x64.

The AV was due to the following sequence of events, all revolving
around `rb_ensure`.

1. `PUSH_TAG();` creates a local `_tag` on the stack, and sets `th->tag` to
   its address.
2. `EXEC_TAG();` calls `setjmp` on this `_tag` object
3. result = (*b_proc) (data1); fails with LoadError (calls
   `load_file_internal` with a nonexistent file, intentionally), setting
   state to 6.
4. `POP_TAG();` resets `th->tag` to NULL.
5.  

    ~~~c
    if (state)
    	JUMP_TAG(state);
    ~~~

    executes, looks up the current thread, and tries to jump to

    ~~~c
        ruby_longjmp(th->tag->buf, 1);
    ~~~

    but `th->tag` is `NULL`, due to (4) above! So we AV when trying to get `th->tag->buf`.




-- 
https://bugs.ruby-lang.org/