[#110736] Can't sign in to bugs.ruby-lang.org — Daniel Berger <djberg96@...>
Hi,
4 messages
2022/11/13
[ruby-core:111068] [Ruby master Bug#19156] ObjectSpace.dump_all segfault during string inspection
From:
"byroot (Jean Boussier)" <noreply@...>
Date:
2022-11-29 15:12:33 UTC
List:
ruby-core #111068
Issue #19156 has been updated by byroot (Jean Boussier).
I can't be bothered to create an account to submit a PR, but I suspect the =
following diff should fix your bug:
```ruby
diff --git a/ext/fast_mmaped_file/mmap.c b/ext/fast_mmaped_file/mmap.c
index 213281c..a3f646f 100644
--- a/ext/fast_mmaped_file/mmap.c
+++ b/ext/fast_mmaped_file/mmap.c
@@ -44,6 +44,8 @@ static VALUE mm_str(VALUE obj, int modify) {
if (i_mm->t->flag & MM_FROZEN) rb_error_frozen("mmap");
}
ret =3D rb_obj_alloc(rb_cString);
+ rb_ivar_set(ret, obj);
+
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;
```
TL;DR; you store the object that hold the mmaped region as an instance vari=
able on the String, ensuring it's not garbage collected until the string is=
too.
It's quite dirty but at this point...
----------------------------------------
Bug #19156: ObjectSpace.dump_all segfault during string inspection
https://bugs.ruby-lang.org/issues/19156#change-100328
* 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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