[#110736] Can't sign in to bugs.ruby-lang.org — Daniel Berger <djberg96@...>
Hi,
4 messages
2022/11/13
[ruby-core:111067] [Ruby master Bug#19156] ObjectSpace.dump_all segfault during string inspection
From:
"byroot (Jean Boussier)" <noreply@...>
Date:
2022-11-29 15:06:29 UTC
List:
ruby-core #111067
Issue #19156 has been updated by byroot (Jean Boussier).
Ok, I found the function that cause this bug:
```c
static VALUE mm_str(VALUE obj, int modify) {
mm_ipc *i_mm;
VALUE ret =3D Qnil;
GET_MMAP(obj, i_mm, modify & ~MM_ORIGIN);
if (modify & MM_MODIFY) {
if (i_mm->t->flag & MM_FROZEN) rb_error_frozen("mmap");
}
ret =3D rb_obj_alloc(rb_cString);
RSTRING(ret)->as.heap.ptr =3D i_mm->t->addr;
RSTRING(ret)->as.heap.aux.capa =3D i_mm->t->len;
RSTRING(ret)->as.heap.len =3D i_mm->t->real;
DEBUGF("RString capa: %d, len: %d", RSTRING(ret)->as.heap.aux.capa, RST=
RING(ret)->as.heap.len);
if (modify & MM_ORIGIN) {
#if HAVE_RB_DEFINE_ALLOC_FUNC
RSTRING(ret)->as.heap.aux.shared =3D obj;
FL_SET(ret, RSTRING_NOEMBED);
FL_SET(ret, FL_USER18);
#else
RSTRING(ret)->orig =3D ret;
#endif
}
if (i_mm->t->flag & MM_FROZEN) {
ret =3D rb_obj_freeze(ret);
}
return ret;
}
```
It's even worse than using `str_new_static`, it's creating a regular string=
and rewriting the pointer. This is terrible code.
----------------------------------------
Bug #19156: ObjectSpace.dump_all segfault during string inspection
https://bugs.ruby-lang.org/issues/19156#change-100327
* Author: mk (Matthias K=E4ppler)
* Status: Third Party's Issue
* Priority: Normal
* ruby -v: ruby 3.0.4p208 (2022-04-12 revision 3fa771dded) [x86_64-linux]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
I am working on a feature that would allow our application to capture heap =
dumps during shutdown for later inspection.
These heap dumps are captured via `ObjectSpace.dump_all(output: io)`. While=
walking the object space, MRI occasionally segfaults while inspecting stri=
ng objects in `search_nonascii` of `string.c`:
```
/usr/local/lib/ruby/3.0.0/objspace.rb:87: [BUG] Segmentation fault at 0x000=
07efee4201000
ruby 3.0.4p208 (2022-04-12 revision 3fa771dded) [x86_64-linux]
...
-- Control frame information -----------------------------------------------
c:0053 p:---- s:0312 e:000311 CFUNC :_dump_all
c:0052 p:0130 s:0305 e:000304 METHOD /usr/local/lib/ruby/3.0.0/objspace.rb:=
87
c:0051 p:0023 s:0295 e:000294 METHOD /home/git/gitlab/lib/gitlab/memory/rep=
orts/heap_dump.rb:26
...
-- C level backtrace information -------------------------------------------
/usr/local/lib/libruby.so.3.0(rb_print_backtrace+0x11) [0x7efee4ad0c5e] vm_=
dump.c:758
/usr/local/lib/libruby.so.3.0(rb_vm_bugreport) vm_dump.c:998
/usr/local/lib/libruby.so.3.0(rb_bug_for_fatal_signal+0xf8) [0x7efee48d0b08=
] error.c:787
/usr/local/lib/libruby.so.3.0(sigsegv+0x55) [0x7efee4a23db5] signal.c:963
/lib/x86_64-linux-gnu/libpthread.so.0(__restore_rt+0x0) [0x7efee4f12140] ..=
/sysdeps/pthread/funlockfile.c:28
/usr/local/lib/libruby.so.3.0(search_nonascii+0x30) [0x7efee4a3ca60] string=
.c:552
/usr/local/lib/libruby.so.3.0(coderange_scan) string.c:585
/usr/local/lib/libruby.so.3.0(enc_coderange_scan+0x1b) [0x7efee4a3e28a] str=
ing.c:709
/usr/local/lib/libruby.so.3.0(rb_enc_str_coderange) string.c:727
/usr/local/lib/ruby/3.0.0/x86_64-linux/objspace.so(is_broken_string+0x8) [0=
x7efeced9c304] ../../internal/string.h:116
/usr/local/lib/ruby/3.0.0/x86_64-linux/objspace.so(dump_object) objspace_du=
mp.c:388
/usr/local/lib/ruby/3.0.0/x86_64-linux/objspace.so(heap_i+0x39) [0x7efeced9=
caa9] objspace_dump.c:521
/usr/local/lib/libruby.so.3.0(objspace_each_objects_without_setup+0xaf) [0x=
7efee48e878f] gc.c:3232
/usr/local/lib/libruby.so.3.0(objspace_each_objects_protected+0x14) [0x7efe=
e48e87c4] gc.c:3242
/usr/local/lib/libruby.so.3.0(rb_ensure+0x12a) [0x7efee48d96aa] eval.c:1162
/usr/local/lib/libruby.so.3.0(objspace_each_objects+0x28) [0x7efee48fb458] =
gc.c:3310
/usr/local/lib/libruby.so.3.0(rb_objspace_each_objects) gc.c:3298
/usr/local/lib/ruby/3.0.0/x86_64-linux/objspace.so(objspace_dump_all+0x88) =
[0x7efeced9b068] objspace_dump.c:616
...
```
Unfortunately I couldn't get my hands on that memory region to see which st=
rings are causing this since this doesn't always happen.
I suspect this is also a problem with MRI master since the code looks uncha=
nged from 3.0.4.
--=20
https://bugs.ruby-lang.org/
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