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This changeset makes no difference unless GC_DEBUG is on. When that flag is set, struct RVALUE is bigger than struct RObject. We have to take care of the additional fields. Otherwise we get a SIGSEGV like shown below. The way obj is initialized in this patch works for both GC_DEBUG is on and off. See also ISO/IEC 9899:1999 section 6.7.8 paragraph #21. ``` Program received signal SIGSEGV, Segmentation fault. __strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:62 62 ../sysdeps/x86_64/multiarch/strlen-avx2.S: No such file or directory (gdb) bt #0 __strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:62 #1 0x00005555557dd9a7 in BSD_vfprintf (fp=0x7fffffff6be0, fmt0=0x5555558f3059 "@%s:%d", ap=0x7fffffff6dd0) at vsnprintf.c:1027 #2 0x00005555557db6f5 in ruby_do_vsnprintf (str=0x555555bfc58d <obj_info_buffers+1325> "", n=211, fmt=0x5555558f3059 "@%s:%d", ap=0x7fffffff6dd0) at sprintf.c:1022 #3 0x00005555557db909 in ruby_snprintf (str=0x555555bfc58d <obj_info_buffers+1325> "", n=211, fmt=0x5555558f3059 "@%s:%d") at sprintf.c:1040 #4 0x0000555555661ef4 in rb_raw_obj_info (buff=0x555555bfc560 <obj_info_buffers+1280> "0x0000555555d2bfa0 [0 ] T_STRING (String)", buff_size=256, obj=93825000456096) at gc.c:11449 #5 0x000055555565baaf in obj_info (obj=93825000456096) at gc.c:11612 #6 0x000055555565bae1 in rgengc_remembered (objspace=0x555555c0a1c0, obj=93825000456096) at gc.c:6618 #7 0x0000555555666987 in newobj_init (klass=93824999964192, flags=5, v1=0, v2=0, v3=0, wb_protected=1, objspace=0x555555c0a1c0, obj=93825000456096) at gc.c:2134 #8 0x0000555555666e49 in newobj_slowpath (klass=93824999964192, flags=5, v1=0, v2=0, v3=0, objspace=0x555555c0a1c0, wb_protected=1) at gc.c:2209 #9 0x0000555555666b94 in newobj_slowpath_wb_protected (klass=93824999964192, flags=5, v1=0, v2=0, v3=0, objspace=0x555555c0a1c0) at gc.c:2220 #10 0x000055555565751b in newobj_of (klass=93824999964192, flags=5, v1=0, v2=0, v3=0, wb_protected=1) at gc.c:2256 #11 0x00005555556575ca in rb_wb_protected_newobj_of (klass=93824999964192, flags=5) at gc.c:2272 #12 0x00005555557f36ea in str_alloc (klass=93824999964192) at string.c:728 #13 0x00005555557f2128 in rb_str_buf_new (capa=0) at string.c:1317 #14 0x000055555578c66d in rb_reg_preprocess (p=0x555555cc8148 "^-(.)(.+)?", end=0x555555cc8152 "", enc=0x555555cc7c80, fixed_enc=0x7fffffff74e8, err=0x7fffffff75f0 "") at re.c:2682 #15 0x000055555578ea13 in rb_reg_initialize (obj=93825000046736, s=0x555555cc8148 "^-(.)(.+)?", len=10, enc=0x555555cc7c80, options=0, err=0x7fffffff75f0 "", sourcefile=0x555555d1a5c0 "lib/optparse.rb", sourceline=1460) at re.c:2808 #16 0x000055555578e285 in rb_reg_initialize_str (obj=93825000046736, str=93825000046904, options=0, err=0x7fffffff75f0 "", sourcefile=0x555555d1a5c0 "lib/optparse.rb", sourceline=1460) at re.c:2869 #17 0x000055555578ee02 in rb_reg_compile (str=93825000046904, options=0, sourcefile=0x555555d1a5c0 "lib/optparse.rb", sourceline=1460) at re.c:2958 #18 0x0000555555748dfb in rb_parser_reg_compile (p=0x555555d1f760, str=93825000046904, options=0) at parse.y:12157 #19 0x00005555557581c3 in parser_reg_compile (p=0x555555d1f760, str=93825000046904, options=0) at parse.y:12151 #20 0x00005555557580ac in reg_compile (p=0x555555d1f760, str=93825000046904, options=0) at parse.y:12167 #21 0x0000555555746ebb in new_regexp (p=0x555555d1f760, node=0x555555dece68, options=0, loc=0x7fffffff89e8) at parse.y:10072 #22 0x000055555573d1f5 in ruby_yyparse (p=0x555555d1f760) at parse.y:4395 #23 0x000055555574a582 in yycompile0 (arg=93825000404832) at parse.y:5945 #24 0x00005555558c6898 in rb_suppress_tracing (func=0x55555574a470 <yycompile0>, arg=93825000404832) at vm_trace.c:427 #25 0x0000555555748290 in yycompile (vparser=93824999283456, p=0x555555d1f760, fname=93824999283624, line=1) at parse.y:5994 #26 0x00005555557481ae in rb_parser_compile_file_path (vparser=93824999283456, fname=93824999283624, file=93824999283400, start=1) at parse.y:6098 #27 0x00005555557cdd35 in load_file_internal (argp_v=140737488331760) at ruby.c:2023 #28 0x00005555556438c5 in rb_ensure (b_proc=0x5555557cd610 <load_file_internal>, data1=140737488331760, e_proc=0x5555557cddd0 <restore_load_file>, data2=140737488331760) at eval.c:1128 ruby#29 0x00005555557cb68b in load_file (parser=93824999283456, fname=93824999283624, f=93824999283400, script=0, opt=0x7fffffffa468) at ruby.c:2142 ruby#30 0x00005555557cb339 in rb_parser_load_file (parser=93824999283456, fname_v=93824999283624) at ruby.c:2164 ruby#31 0x00005555556ba3e1 in load_iseq_eval (ec=0x555555c0a650, fname=93824999283624) at load.c:579 ruby#32 0x00005555556b857a in require_internal (ec=0x555555c0a650, fname=93824999284352, exception=1) at load.c:1016 ruby#33 0x00005555556b7967 in rb_require_string (fname=93824999284464) at load.c:1105 ruby#34 0x00005555556b7939 in rb_f_require (obj=93824999994824, fname=93824999284464) at load.c:811 ruby#35 0x00005555558b7ae0 in call_cfunc_1 (recv=93824999994824, argc=1, argv=0x7ffff7ecd0a8, func=0x5555556b7920 <rb_f_require>) at vm_insnhelper.c:2348 ruby#36 0x00005555558a8889 in vm_call_cfunc_with_frame (ec=0x555555c0a650, reg_cfp=0x7ffff7fccfa0, calling=0x7fffffffaab0, cd=0x555555d76a10, empty_kw_splat=0) at vm_insnhelper.c:2513 ruby#37 0x000055555589fb5c in vm_call_cfunc (ec=0x555555c0a650, reg_cfp=0x7ffff7fccfa0, calling=0x7fffffffaab0, cd=0x555555d76a10) at vm_insnhelper.c:2538 ruby#38 0x000055555589f22e in vm_call_method_each_type (ec=0x555555c0a650, cfp=0x7ffff7fccfa0, calling=0x7fffffffaab0, cd=0x555555d76a10) at vm_insnhelper.c:2924 ruby#39 0x000055555589ef47 in vm_call_method (ec=0x555555c0a650, cfp=0x7ffff7fccfa0, calling=0x7fffffffaab0, cd=0x555555d76a10) at vm_insnhelper.c:3038 ruby#40 0x0000555555866dbd in vm_call_general (ec=0x555555c0a650, reg_cfp=0x7ffff7fccfa0, calling=0x7fffffffaab0, cd=0x555555d76a10) at vm_insnhelper.c:3075 ruby#41 0x00005555558ae557 in vm_sendish (ec=0x555555c0a650, reg_cfp=0x7ffff7fccfa0, cd=0x555555d76a10, block_handler=0, method_explorer=0x5555558ae5d0 <vm_search_method_wrap>) at vm_insnhelper.c:4021 ruby#42 0x000055555587745b in vm_exec_core (ec=0x555555c0a650, initial=0) at insns.def:801 ruby#43 0x0000555555899b9c in rb_vm_exec (ec=0x555555c0a650, mjit_enable_p=1) at vm.c:1907 ruby#44 0x000055555589aaf0 in rb_iseq_eval_main (iseq=0x555555c1da80) at vm.c:2166 ruby#45 0x0000555555641f0b in rb_ec_exec_node (ec=0x555555c0a650, n=0x555555c1da80) at eval.c:277 ruby#46 0x0000555555641d62 in ruby_run_node (n=0x555555c1da80) at eval.c:335 ruby#47 0x000055555557a188 in main (argc=11, argv=0x7fffffffc848) at main.c:50 (gdb) fr 7 #7 0x0000555555666987 in newobj_init (klass=93824999964192, flags=5, v1=0, v2=0, v3=0, wb_protected=1, objspace=0x555555c0a1c0, obj=93825000456096) at gc.c:2134 2134 if (rgengc_remembered(objspace, (VALUE)obj)) rb_bug("newobj: %s is remembered.", obj_info(obj)); (gdb) p ((struct RVALUE*)obj)->file $1 = 0x65a5992b0fb25ce7 <error: Cannot access memory at address 0x65a5992b0fb25ce7> (gdb) ```
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Jun 11, 2020
This reverts commit 02b216e. This reverts commit 9b8825b. I found that combining sweep and move is not safe. I don't think that we can do compaction concurrently with _anything_ unless there is a read barrier installed. Here is a simple example. A class object is freed, and during it's free step, it tries to remove itself from its parent's subclass list. However, during the sweep step, the parent class was moved and the "currently being freed" class didn't have references updated yet. So we get a segv like this: ``` (lldb) bt * thread #1, name = 'ruby', stop reason = signal SIGSEGV * frame #0: 0x0000560763e344cb ruby`rb_st_lookup at st.c:320:43 frame #1: 0x0000560763e344cb ruby`rb_st_lookup(tab=0x2f7469672f6e6f72, key=3809, value=0x0000560765bf2270) at st.c:1010 frame #2: 0x0000560763e8f16a ruby`rb_search_class_path at variable.c:99:9 frame #3: 0x0000560763e8f141 ruby`rb_search_class_path at variable.c:145 frame #4: 0x0000560763e8f141 ruby`rb_search_class_path(klass=94589785585880) at variable.c:191 frame #5: 0x0000560763ec744e ruby`rb_vm_bugreport at vm_dump.c:996:17 frame #6: 0x0000560763f5b958 ruby`rb_bug_for_fatal_signal at error.c:675:5 frame #7: 0x0000560763e27dad ruby`sigsegv(sig=<unavailable>, info=<unavailable>, ctx=<unavailable>) at signal.c:955:5 frame #8: 0x00007f8b891d33c0 libpthread.so.0`___lldb_unnamed_symbol1$$libpthread.so.0 + 1 frame #9: 0x0000560763efa8bb ruby`rb_class_remove_from_super_subclasses(klass=94589790314280) at class.c:93:56 frame #10: 0x0000560763d10cb7 ruby`gc_sweep_step at gc.c:2674:2 frame #11: 0x0000560763d1187b ruby`gc_sweep at gc.c:4540:2 frame #12: 0x0000560763d101f0 ruby`gc_start at gc.c:6797:6 frame #13: 0x0000560763d15153 ruby`rb_gc_compact at gc.c:7479:12 frame #14: 0x0000560763eb4eb8 ruby`vm_exec_core at vm_insnhelper.c:5183:13 frame #15: 0x0000560763ea9bae ruby`rb_vm_exec at vm.c:1953:22 frame #16: 0x0000560763eac08d ruby`rb_yield at vm.c:1132:9 frame #17: 0x0000560763edb4f2 ruby`rb_ary_collect at array.c:3186:9 frame #18: 0x0000560763e9ee15 ruby`vm_call_cfunc_with_frame at vm_insnhelper.c:2575:12 frame #19: 0x0000560763eb2e66 ruby`vm_exec_core at vm_insnhelper.c:4177:11 frame #20: 0x0000560763ea9bae ruby`rb_vm_exec at vm.c:1953:22 frame #21: 0x0000560763eac08d ruby`rb_yield at vm.c:1132:9 frame #22: 0x0000560763edb4f2 ruby`rb_ary_collect at array.c:3186:9 frame #23: 0x0000560763e9ee15 ruby`vm_call_cfunc_with_frame at vm_insnhelper.c:2575:12 frame #24: 0x0000560763eb2e66 ruby`vm_exec_core at vm_insnhelper.c:4177:11 frame #25: 0x0000560763ea9bae ruby`rb_vm_exec at vm.c:1953:22 frame #26: 0x0000560763ceee01 ruby`rb_ec_exec_node(ec=0x0000560765afa530, n=0x0000560765b088e0) at eval.c:296:2 frame #27: 0x0000560763cf3b7b ruby`ruby_run_node(n=0x0000560765b088e0) at eval.c:354:12 frame #28: 0x0000560763cee4a3 ruby`main(argc=<unavailable>, argv=<unavailable>) at main.c:50:9 frame ruby#29: 0x00007f8b88e560b3 libc.so.6`__libc_start_main + 243 frame ruby#30: 0x0000560763cee4ee ruby`_start + 46 (lldb) f 9 frame #9: 0x0000560763efa8bb ruby`rb_class_remove_from_super_subclasses(klass=94589790314280) at class.c:93:56 90 91 *RCLASS_EXT(klass)->parent_subclasses = entry->next; 92 if (entry->next) { -> 93 RCLASS_EXT(entry->next->klass)->parent_subclasses = RCLASS_EXT(klass)->parent_subclasses; 94 } 95 xfree(entry); 96 } (lldb) command script import -r misc/lldb_cruby.py lldb scripts for ruby has been installed. (lldb) rp entry->next->klass (struct RMoved) $1 = (flags = 30, destination = 94589792806680, next = 94589784369160) (lldb) ```
k0kubun
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Nov 21, 2020
GitHub: fix GH-15 Reported by Eneroth3. Thanks!!! ruby/fiddle@f3d70b81ec
k0kubun
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Apr 28, 2021
* Resolve shared mixed_names.rb * Add long option with negation * Show --help for all examples * Table of contents for tutorial * Move argument converters to separate rdoc * Add references to argument_converters.rdoc * Tune up argument converters * Change explicit links to auto-links ruby/optparse@c91ed8d33d
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Apr 28, 2021
This commit adds a check on the ep just like in the mark function. The env can contain null bytes if allocation tracing is enabled. We're seeing errors during autocompaction like this: ``` (lldb) bt 40 * thread #1, name = 'ruby', stop reason = signal SIGABRT frame #0: 0x00007f7d64b6018b libc.so.6`raise + 203 frame #1: 0x00007f7d64b3f859 libc.so.6`abort + 299 frame #2: 0x000055af5f2fefc9 ruby`die at error.c:764:5 frame #3: 0x000055af5f2ff1ac ruby`rb_bug_for_fatal_signal(default_sighandler=0x0000000000000000, sig=11, ctx=0x000055af60bc3340, fmt="") at error.c:804:5 frame #4: 0x000055af5f4bd08f ruby`sigsegv(sig=11, info=0x000055af60bc3470, ctx=0x000055af60bc3340) at signal.c:960:5 frame #5: 0x00007f7d64ebe3c0 libpthread.so.0`__restore_rt frame #6: 0x000055af5f339b0a ruby`gc_ref_update_imemo(objspace=0x000055af60b2b040, obj=0x00007f7d5b513fd0) at gc.c:9046:13 frame #7: 0x000055af5f339172 ruby`gc_update_object_references(objspace=0x000055af60b2b040, obj=0x00007f7d5b513fd0) at gc.c:9307:9 frame #8: 0x000055af5f338e79 ruby`gc_ref_update(vstart=0x00007f7d5b510010, vend=0x00007f7d5b513ff8, stride=40, objspace=0x000055af60b2b040, page=0x000055af62577aa0) at gc.c:9452:21 frame #9: 0x000055af5f337846 ruby`gc_update_references(objspace=0x000055af60b2b040, heap=0x000055af60b2b068) at gc.c:9481:9 frame #10: 0x000055af5f336569 ruby`gc_compact_finish(objspace=0x000055af60b2b040, heap=0x000055af60b2b068) at gc.c:4840:5 frame #11: 0x000055af5f335efb ruby`gc_page_sweep(objspace=0x000055af60b2b040, heap=0x000055af60b2b068, sweep_page=0x000055af63a1eb30) at gc.c:5046:13 frame #12: 0x000055af5f3355c5 ruby`gc_sweep_step(objspace=0x000055af60b2b040, heap=0x000055af60b2b068) at gc.c:5214:19 frame #13: 0x000055af5f33daf6 ruby`gc_sweep_rest(objspace=0x000055af60b2b040) at gc.c:5271:2 frame #14: 0x000055af5f33cacd ruby`gc_sweep(objspace=0x000055af60b2b040) at gc.c:5389:2 frame #15: 0x000055af5f33c21d ruby`gc_marks_rest(objspace=0x000055af60b2b040) at gc.c:7555:5 frame #16: 0x000055af5f324d41 ruby`gc_rest(objspace=0x000055af60b2b040) at gc.c:8457:13 frame #17: 0x000055af5f3297d8 ruby`garbage_collect(objspace=0x000055af60b2b040, reason=45568) at gc.c:8318:9 frame #18: 0x000055af5f344ece ruby`garbage_collect_with_gvl(objspace=0x000055af60b2b040, reason=45568) at gc.c:8632:9 frame #19: 0x000055af5f344e61 ruby`objspace_malloc_gc_stress(objspace=0x000055af60b2b040) at gc.c:10592:9 frame #20: 0x000055af5f32ced1 ruby`objspace_xmalloc0(objspace=0x000055af60b2b040, size=64) at gc.c:10767:5 frame #21: 0x000055af5f32ce11 ruby`ruby_xmalloc0(size=64) at gc.c:10988:12 frame #22: 0x000055af5f32cdac ruby`ruby_xmalloc_body(size=64) at gc.c:10997:12 frame #23: 0x000055af5f329415 ruby`ruby_xmalloc(size=64) at gc.c:12942:12 frame #24: 0x00007f7d611c4fe5 objspace.so`newobj_i(tpval=0x00007f7d5b553770, data=0x000055af639031a0) at object_tracing.c:101:35 frame #25: 0x000055af5f5b283f ruby`tp_call_trace(tpval=0x00007f7d5b553770, trace_arg=0x00007fff1016d398) at vm_trace.c:1115:2 frame #26: 0x000055af5f5b50ec ruby`exec_hooks_body(ec=0x000055af60b2b700, list=0x000055af60b2b920, trace_arg=0x00007fff1016d398) at vm_trace.c:304:3 frame #27: 0x000055af5f5b0f24 ruby`exec_hooks_unprotected(ec=0x000055af60b2b700, list=0x000055af60b2b920, trace_arg=0x00007fff1016d398) at vm_trace.c:333:5 frame #28: 0x000055af5f5b0da8 ruby`rb_exec_event_hooks(trace_arg=0x00007fff1016d398, hooks=0x000055af60b2b920, pop_p=0) at vm_trace.c:378:13 frame ruby#29: 0x000055af5f33f8e2 ruby`rb_exec_event_hook_orig(ec=0x000055af60b2b700, hooks=0x000055af60b2b920, flag=1048576, self=0x00007f7d5b5c08c0, id=0, called_id=0, klass=0x0000000000000000, data=0x00007f7d5b513fd0, pop_p=0) at vm_core.h:1989:5 frame ruby#30: 0x000055af5f334975 ruby`gc_event_hook_body(ec=0x000055af60b2b700, objspace=0x000055af60b2b040, event=1048576, data=0x00007f7d5b513fd0) at gc.c:2083:5 * frame ruby#31: 0x000055af5f3342df ruby`newobj_slowpath_wb_protected [inlined] newobj_slowpath(klass=0x00007f7d5b9d19c8, flags=0x000000000000001a, objspace=0x000055af60b2b040, cr=0x000055af60b2b910, wb_protected=1) at gc.c:2284:9 frame ruby#32: 0x000055af5f33410f ruby`newobj_slowpath_wb_protected(klass=0x00007f7d5b9d19c8, flags=0x000000000000001a, objspace=0x000055af60b2b040, cr=0x000055af60b2b910) at gc.c:2299 frame ruby#33: 0x000055af5f333de9 ruby`newobj_of0(klass=0x00007f7d5b9d19c8, flags=0x000000000000001a, wb_protected=1, cr=0x000055af60b2b910) at gc.c:2338:11 frame ruby#34: 0x000055af5f3227ae ruby`newobj_of(klass=0x00007f7d5b9d19c8, flags=0x000000000000001a, v1=0x000055af657d88a0, v2=0x000055af657d8890, v3=0x0000000000000000, wb_protected=1) at gc.c:2348:17 frame ruby#35: 0x000055af5f322c5b ruby`rb_imemo_new(type=imemo_env, v1=0x000055af657d88a0, v2=0x000055af657d8890, v3=0x0000000000000000, v0=0x00007f7d5b9d19c8) at gc.c:2434:12 frame ruby#36: 0x000055af5f5a3925 ruby`vm_env_new(env_ep=0x000055af657d88a0, env_body=0x000055af657d8890, env_size=4, iseq=0x00007f7d5b9d19c8) at vm_core.h:1363:33 frame ruby#37: 0x000055af5f5a3808 ruby`vm_make_env_each(ec=0x000055af60b2b700, cfp=0x00007f7d6482fc90) at vm.c:801:11 frame ruby#38: 0x000055af5f5a368d ruby`vm_make_env_each(ec=0x000055af60b2b700, cfp=0x00007f7d6482fc20) at vm.c:752:13 frame ruby#39: 0x000055af5f5a368d ruby`vm_make_env_each(ec=0x000055af60b2b700, cfp=0x00007f7d6482fbb0) at vm.c:752:13 (lldb) f 31 frame ruby#31: 0x000055af5f3342df ruby`newobj_slowpath_wb_protected [inlined] newobj_slowpath(klass=0x00007f7d5b9d19c8, flags=0x000000000000001a, objspace=0x000055af60b2b040, cr=0x000055af60b2b910, wb_protected=1) at gc.c:2284:9 2281 } 2282 GC_ASSERT(obj != 0); 2283 newobj_init(klass, flags, wb_protected, objspace, obj); -> 2284 gc_event_hook_prep(objspace, RUBY_INTERNAL_EVENT_NEWOBJ, obj, newobj_fill(obj, 0, 0, 0)); 2285 } 2286 RB_VM_LOCK_LEAVE_CR_LEV(cr, &lev); 2287 (lldb) p obj (VALUE) $3 = 0x00007f7d5b513fd0 (lldb) f 6 frame #6: 0x000055af5f339b0a ruby`gc_ref_update_imemo(objspace=0x000055af60b2b040, obj=0x00007f7d5b513fd0) at gc.c:9046:13 9043 { 9044 rb_env_t *env = (rb_env_t *)obj; 9045 TYPED_UPDATE_IF_MOVED(objspace, rb_iseq_t *, env->iseq); -> 9046 UPDATE_IF_MOVED(objspace, env->ep[VM_ENV_DATA_INDEX_ENV]); 9047 gc_update_values(objspace, (long)env->env_size, (VALUE *)env->env); 9048 } 9049 break; (lldb) p obj (VALUE) $4 = 0x00007f7d5b513fd0 (lldb) ```
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Nov 1, 2022
Always look up instance variable buffers when iterating. It is possible for the instance variable buffer to change out from under the object during iteration, so we cannot cache the buffer on the stack. In the case of Bug #19095, the transient heap moved the buffer during iteration: ``` Watchpoint 1 hit: old value: 0x0000000107c00df8 new value: 0x00000001032743c0 Process 31720 stopped * thread #1, queue = 'com.apple.main-thread', stop reason = watchpoint 1 frame #0: 0x00000001006e5178 miniruby`rb_obj_transient_heap_evacuate(obj=0x000000010d6b94b0, promote=1) at variable.c:1361:5 1358 } 1359 MEMCPY(new_ptr, old_ptr, VALUE, len); 1360 ROBJECT(obj)->as.heap.ivptr = new_ptr; -> 1361 } 1362 } 1363 #endif 1364 miniruby`rb_obj_transient_heap_evacuate: -> 0x1006e5178 <+328>: b 0x1006e517c ; <+332> at variable.c:1362:1 0x1006e517c <+332>: ldp x29, x30, [sp, #0x50] 0x1006e5180 <+336>: add sp, sp, #0x60 0x1006e5184 <+340>: ret Target 0: (miniruby) stopped. (lldb) bt * thread #1, queue = 'com.apple.main-thread', stop reason = watchpoint 1 * frame #0: 0x00000001006e5178 miniruby`rb_obj_transient_heap_evacuate(obj=0x000000010d6b94b0, promote=1) at variable.c:1361:5 frame #1: 0x00000001006cb150 miniruby`transient_heap_block_evacuate(theap=0x0000000100b196c0, block=0x0000000107c00000) at transient_heap.c:734:17 frame #2: 0x00000001006c854c miniruby`transient_heap_evacuate(dmy=0x0000000000000000) at transient_heap.c:808:17 frame #3: 0x00000001007fe6c0 miniruby`rb_postponed_job_flush(vm=0x0000000104402900) at vm_trace.c:1773:21 frame #4: 0x0000000100637a84 miniruby`rb_threadptr_execute_interrupts(th=0x0000000103803bc0, blocking_timing=0) at thread.c:2316:13 frame #5: 0x000000010078b730 miniruby`rb_vm_check_ints(ec=0x00000001048038d0) at vm_core.h:2025:9 frame #6: 0x00000001006fbd10 miniruby`vm_pop_frame(ec=0x00000001048038d0, cfp=0x0000000104a04440, ep=0x0000000104904a28) at vm_insnhelper.c:422:5 frame #7: 0x00000001006fbca0 miniruby`rb_vm_pop_frame(ec=0x00000001048038d0) at vm_insnhelper.c:431:5 frame #8: 0x00000001007d6420 miniruby`vm_call0_cfunc_with_frame(ec=0x00000001048038d0, calling=0x000000016fdcc6a0, argv=0x0000000000000000) at vm_eval.c:153:9 frame #9: 0x00000001007d44cc miniruby`vm_call0_cfunc(ec=0x00000001048038d0, calling=0x000000016fdcc6a0, argv=0x0000000000000000) at vm_eval.c:164:12 frame #10: 0x0000000100766e80 miniruby`vm_call0_body(ec=0x00000001048038d0, calling=0x000000016fdcc6a0, argv=0x0000000000000000) at vm_eval.c:210:15 frame #11: 0x00000001007d76f0 miniruby`vm_call0_cc(ec=0x00000001048038d0, recv=0x000000010d6b49d8, id=2769, argc=0, argv=0x0000000000000000, cc=0x000000010d6b2e58, kw_splat=0) at vm_eval.c:87:12 frame #12: 0x0000000100769e48 miniruby`rb_funcallv_scope(recv=0x000000010d6b49d8, mid=2769, argc=0, argv=0x0000000000000000, scope=CALL_FCALL) at vm_eval.c:1051:16 frame #13: 0x0000000100760a54 miniruby`rb_funcallv(recv=0x000000010d6b49d8, mid=2769, argc=0, argv=0x0000000000000000) at vm_eval.c:1066:12 frame #14: 0x000000010037513c miniruby`rb_inspect(obj=0x000000010d6b49d8) at object.c:633:34 frame #15: 0x000000010002c950 miniruby`inspect_ary(ary=0x000000010d6b4938, dummy=0x0000000000000000, recur=0) at array.c:3091:13 frame #16: 0x0000000100642020 miniruby`exec_recursive(func=(miniruby`inspect_ary at array.c:3084), obj=0x000000010d6b4938, pairid=0x0000000000000000, arg=0x0000000000000000, outer=0, mid=2769) at thread.c:5177:23 frame #17: 0x00000001006412fc miniruby`rb_exec_recursive(func=(miniruby`inspect_ary at array.c:3084), obj=0x000000010d6b4938, arg=0x0000000000000000) at thread.c:5205:12 frame #18: 0x00000001000127f0 miniruby`rb_ary_inspect(ary=0x000000010d6b4938) at array.c:3117:12 ``` In general though, any calls back out to the interpreter could change the IV buffer, so it's not safe to cache. [Bug #19095]
k0kubun
pushed a commit
that referenced
this pull request
Oct 15, 2023
to avoid deadlock
```ruby
r = Ractor.new do
obj = Thread.new{}
Ractor.yield obj
rescue => e
e.message
end
p r.take
```
```
(lldb) bt
* thread #1, name = 'miniruby', stop reason = signal SIGSTOP
* frame #0: 0x0000ffff44881410 libpthread.so.0`__lll_lock_wait + 88
frame #1: 0x0000ffff4487a078 libpthread.so.0`__pthread_mutex_lock + 232
frame #2: 0x0000aaab617c0980 miniruby`rb_native_mutex_lock(lock=<unavailable>) at thread_pthread.c:109:14
frame #3: 0x0000aaab617c1d58 miniruby`ubf_event_waiting [inlined] thread_sched_lock_(th=0x0000aaab9df82980, file=<unavailable>, line=46, sched=0x0000aaab9dec79b8) at thread_pthread.c:351:5
frame #4: 0x0000aaab617c1d50 miniruby`ubf_event_waiting(ptr=0x0000aaab9df82980) at thread_pthread_mn.c:46:5
frame #5: 0x0000aaab617c6020 miniruby`rb_threadptr_interrupt [inlined] rb_threadptr_interrupt_common(trap=0, th=0x0000aaab9df82980) at thread.c:352:25
frame #6: 0x0000aaab617c5fec miniruby`rb_threadptr_interrupt(th=0x0000aaab9df82980) at thread.c:365:5
frame #7: 0x0000aaab617379b0 miniruby`rb_ractor_terminate_all at ractor.c:2364:13
frame #8: 0x0000aaab6173797c miniruby`rb_ractor_terminate_all at ractor.c:2383:17
frame #9: 0x0000aaab61737958 miniruby`rb_ractor_terminate_all [inlined] ractor_terminal_interrupt_all(vm=0x0000aaab9dea3320) at ractor.c:2375:1
frame #10: 0x0000aaab61737950 miniruby`rb_ractor_terminate_all at ractor.c:2424:13
frame #11: 0x0000aaab6164f108 miniruby`rb_ec_cleanup(ec=0x0000aaab9dea5900, ex=RUBY_TAG_NONE) at eval.c:239:9
frame #12: 0x0000aaab6164fa3c miniruby`ruby_run_node(n=0x0000ffff417ed178) at eval.c:328:12
frame #13: 0x0000aaab615a5ab0 miniruby`main at main.c:39:12
frame #14: 0x0000aaab615a5a98 miniruby`main(argc=<unavailable>, argv=<unavailable>) at main.c:58:12
frame #15: 0x0000ffff44714b2c libc.so.6`__libc_start_main + 228
frame #16: 0x0000aaab615a5b0c miniruby`_start + 52
(lldb) thread select 3
* thread #3, name = 'bootstraptest.*', stop reason = signal SIGSTOP
frame #0: 0x0000ffff448813ec libpthread.so.0`__lll_lock_wait + 52
libpthread.so.0`__lll_lock_wait:
-> 0xffff448813ec <+52>: svc #0
0xffff448813f0 <+56>: eor w20, w20, #0x80
0xffff448813f4 <+60>: sxtw x20, w20
0xffff448813f8 <+64>: b 0xffff44881414 ; <+92>
(lldb) bt
* thread #3, name = 'bootstraptest.*', stop reason = signal SIGSTOP
* frame #0: 0x0000ffff448813ec libpthread.so.0`__lll_lock_wait + 52
frame #1: 0x0000ffff4487a078 libpthread.so.0`__pthread_mutex_lock + 232
frame #2: 0x0000aaab617c0980 miniruby`rb_native_mutex_lock(lock=<unavailable>) at thread_pthread.c:109:14
frame #3: 0x0000aaab61823d68 miniruby`rb_vm_lock_enter_body [inlined] vm_lock_enter(no_barrier=false, lev=0x0000ffff215bfbe4, locked=false, vm=0x0000aaab9dea3320, cr=0x0000aaab9dec7890) at vm_sync.c:57:9
frame #4: 0x0000aaab61823d60 miniruby`rb_vm_lock_enter_body(lev=0x0000ffff215bfbe4) at vm_sync.c:119:9
frame #5: 0x0000aaab617c1b30 miniruby`thread_sched_setup_running_threads [inlined] rb_vm_lock_enter(file=<unavailable>, line=597, lev=0x0000ffff215bfbe4) at vm_sync.h:75:9
frame #6: 0x0000aaab617c1b14 miniruby`thread_sched_setup_running_threads(vm=0x0000aaab9dea3320, add_th=0x0000aaab9df82980, del_th=<unavailable>, add_timeslice_th=0x0000000000000000, cr=<unavailable>, sched=<unavailable>, sched=<unavailable>) at thread_pthread.c:597:9
frame #7: 0x0000aaab617c29b4 miniruby`thread_sched_wait_running_turn at thread_pthread.c:614:5
frame #8: 0x0000aaab617c298c miniruby`thread_sched_wait_running_turn(sched=0x0000aaab9dec79b8, th=0x0000aaab9df82980, can_direct_transfer=true) at thread_pthread.c:868:9
frame #9: 0x0000aaab617c6f0c miniruby`thread_sched_wait_events(sched=0x0000aaab9dec79b8, th=0x0000aaab9df82980, fd=<unavailable>, events=<unavailable>, rel=<unavailable>) at thread_pthread_mn.c:90:17
frame #10: 0x0000aaab617c7354 miniruby`rb_thread_terminate_all at thread_pthread.c:3248:13
frame #11: 0x0000aaab617c733c miniruby`rb_thread_terminate_all(th=0x0000aaab9df82980) at thread.c:466:13
frame #12: 0x0000aaab617c7a64 miniruby`thread_start_func_2(th=0x0000aaab9df82980, stack_start=<unavailable>) at thread.c:713:9
frame #13: 0x0000aaab617c7d1c miniruby`co_start [inlined] call_thread_start_func_2(th=0x0000aaab9df82980) at thread_pthread.c:2165:5
frame #14: 0x0000aaab617c7cd0 miniruby`co_start(from=<unavailable>, self=0x0000aaab9df0f760) at thread_pthread_mn.c:421:9
```
k0kubun
pushed a commit
that referenced
this pull request
Dec 8, 2024
[Bug #20921]
When we create a cache entry for a constant, the following sequence of
events could happen:
- vm_track_constant_cache is called to insert a constant cache.
- In vm_track_constant_cache, we first look up the ST table for the ID
of the constant. Assume the ST table exists because another iseq also
holds a cache entry for this ID.
- We then insert into this ST table with the iseq_inline_constant_cache.
- However, while inserting into this ST table, it allocates memory, which
could trigger a GC. Assume that it does trigger a GC.
- The GC frees the one and only other iseq that holds a cache entry for
this ID.
- In remove_from_constant_cache, it will appear that the ST table is now
empty because there are no more iseq with cache entries for this ID, so
we free the ST table.
- We complete GC and continue our st_insert. However, this ST table has
been freed so we now have a use-after-free.
This issue is very hard to reproduce, because it requires that the GC runs
at a very specific time. However, we can make it show up by applying this
patch which runs GC right before the st_insert to mimic the st_insert
triggering a GC:
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 3cb23f0..a93998136a 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -6338,6 +6338,10 @@ vm_track_constant_cache(ID id, void *ic)
rb_id_table_insert(const_cache, id, (VALUE)ics);
}
+ if (id == rb_intern("MyConstant")) rb_gc();
+
st_insert(ics, (st_data_t) ic, (st_data_t) Qtrue);
}
And if we run this script:
Object.const_set("MyConstant", "Hello!")
my_proc = eval("-> { MyConstant }")
my_proc.call
my_proc = eval("-> { MyConstant }")
my_proc.call
We can see that ASAN outputs a use-after-free error:
==36540==ERROR: AddressSanitizer: heap-use-after-free on address 0x606000049528 at pc 0x000102f3ceac bp 0x00016d607a70 sp 0x00016d607a68
READ of size 8 at 0x606000049528 thread T0
#0 0x102f3cea8 in do_hash st.c:321
#1 0x102f3ddd0 in rb_st_insert st.c:1132
#2 0x103140700 in vm_track_constant_cache vm_insnhelper.c:6345
#3 0x1030b91d8 in vm_ic_track_const_chain vm_insnhelper.c:6356
#4 0x1030b8cf8 in rb_vm_opt_getconstant_path vm_insnhelper.c:6424
#5 0x1030bc1e0 in vm_exec_core insns.def:263
#6 0x1030b55fc in rb_vm_exec vm.c:2585
#7 0x1030fe0ac in rb_iseq_eval_main vm.c:2851
#8 0x102a82588 in rb_ec_exec_node eval.c:281
#9 0x102a81fe0 in ruby_run_node eval.c:319
#10 0x1027f3db4 in rb_main main.c:43
#11 0x1027f3bd4 in main main.c:68
#12 0x183900270 (<unknown module>)
0x606000049528 is located 8 bytes inside of 56-byte region [0x606000049520,0x606000049558)
freed by thread T0 here:
#0 0x104174d40 in free+0x98 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x54d40)
#1 0x102ada89c in rb_gc_impl_free default.c:8183
#2 0x102ada7dc in ruby_sized_xfree gc.c:4507
#3 0x102ac4d34 in ruby_xfree gc.c:4518
#4 0x102f3cb34 in rb_st_free_table st.c:663
#5 0x102bd52d8 in remove_from_constant_cache iseq.c:119
#6 0x102bbe2cc in iseq_clear_ic_references iseq.c:153
#7 0x102bbd2a0 in rb_iseq_free iseq.c:166
#8 0x102b32ed0 in rb_imemo_free imemo.c:564
#9 0x102ac4b44 in rb_gc_obj_free gc.c:1407
#10 0x102af4290 in gc_sweep_plane default.c:3546
#11 0x102af3bdc in gc_sweep_page default.c:3634
#12 0x102aeb140 in gc_sweep_step default.c:3906
#13 0x102aeadf0 in gc_sweep_rest default.c:3978
#14 0x102ae4714 in gc_sweep default.c:4155
#15 0x102af8474 in gc_start default.c:6484
#16 0x102afbe30 in garbage_collect default.c:6363
#17 0x102ad37f0 in rb_gc_impl_start default.c:6816
#18 0x102ad3634 in rb_gc gc.c:3624
#19 0x1031406ec in vm_track_constant_cache vm_insnhelper.c:6342
#20 0x1030b91d8 in vm_ic_track_const_chain vm_insnhelper.c:6356
#21 0x1030b8cf8 in rb_vm_opt_getconstant_path vm_insnhelper.c:6424
#22 0x1030bc1e0 in vm_exec_core insns.def:263
#23 0x1030b55fc in rb_vm_exec vm.c:2585
#24 0x1030fe0ac in rb_iseq_eval_main vm.c:2851
#25 0x102a82588 in rb_ec_exec_node eval.c:281
#26 0x102a81fe0 in ruby_run_node eval.c:319
#27 0x1027f3db4 in rb_main main.c:43
#28 0x1027f3bd4 in main main.c:68
ruby#29 0x183900270 (<unknown module>)
previously allocated by thread T0 here:
#0 0x104174c04 in malloc+0x94 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x54c04)
#1 0x102ada0ec in rb_gc_impl_malloc default.c:8198
#2 0x102acee44 in ruby_xmalloc gc.c:4438
#3 0x102f3c85c in rb_st_init_table_with_size st.c:571
#4 0x102f3c900 in rb_st_init_table st.c:600
#5 0x102f3c920 in rb_st_init_numtable st.c:608
#6 0x103140698 in vm_track_constant_cache vm_insnhelper.c:6337
#7 0x1030b91d8 in vm_ic_track_const_chain vm_insnhelper.c:6356
#8 0x1030b8cf8 in rb_vm_opt_getconstant_path vm_insnhelper.c:6424
#9 0x1030bc1e0 in vm_exec_core insns.def:263
#10 0x1030b55fc in rb_vm_exec vm.c:2585
#11 0x1030fe0ac in rb_iseq_eval_main vm.c:2851
#12 0x102a82588 in rb_ec_exec_node eval.c:281
#13 0x102a81fe0 in ruby_run_node eval.c:319
#14 0x1027f3db4 in rb_main main.c:43
#15 0x1027f3bd4 in main main.c:68
#16 0x183900270 (<unknown module>)
This commit fixes this bug by adding a inserting_constant_cache_id field
to the VM, which stores the ID that is currently being inserted and, in
remove_from_constant_cache, we don't free the ST table for ID equal to
this one.
Co-Authored-By: Alan Wu <alanwu@ruby-lang.org>
k0kubun
added a commit
that referenced
this pull request
Mar 5, 2025
Fix use-after-free in constant cache [Bug #20921] When we create a cache entry for a constant, the following sequence of events could happen: - vm_track_constant_cache is called to insert a constant cache. - In vm_track_constant_cache, we first look up the ST table for the ID of the constant. Assume the ST table exists because another iseq also holds a cache entry for this ID. - We then insert into this ST table with the iseq_inline_constant_cache. - However, while inserting into this ST table, it allocates memory, which could trigger a GC. Assume that it does trigger a GC. - The GC frees the one and only other iseq that holds a cache entry for this ID. - In remove_from_constant_cache, it will appear that the ST table is now empty because there are no more iseq with cache entries for this ID, so we free the ST table. - We complete GC and continue our st_insert. However, this ST table has been freed so we now have a use-after-free. This issue is very hard to reproduce, because it requires that the GC runs at a very specific time. However, we can make it show up by applying this patch which runs GC right before the st_insert to mimic the st_insert triggering a GC: diff --git a/vm_insnhelper.c b/vm_insnhelper.c index 3cb23f0..a93998136a 100644 --- a/vm_insnhelper.c +++ b/vm_insnhelper.c @@ -6338,6 +6338,10 @@ vm_track_constant_cache(ID id, void *ic) rb_id_table_insert(const_cache, id, (VALUE)ics); } + if (id == rb_intern("MyConstant")) rb_gc(); + st_insert(ics, (st_data_t) ic, (st_data_t) Qtrue); } And if we run this script: Object.const_set("MyConstant", "Hello!") my_proc = eval("-> { MyConstant }") my_proc.call my_proc = eval("-> { MyConstant }") my_proc.call We can see that ASAN outputs a use-after-free error: ==36540==ERROR: AddressSanitizer: heap-use-after-free on address 0x606000049528 at pc 0x000102f3ceac bp 0x00016d607a70 sp 0x00016d607a68 READ of size 8 at 0x606000049528 thread T0 #0 0x102f3cea8 in do_hash st.c:321 #1 0x102f3ddd0 in rb_st_insert st.c:1132 #2 0x103140700 in vm_track_constant_cache vm_insnhelper.c:6345 #3 0x1030b91d8 in vm_ic_track_const_chain vm_insnhelper.c:6356 #4 0x1030b8cf8 in rb_vm_opt_getconstant_path vm_insnhelper.c:6424 #5 0x1030bc1e0 in vm_exec_core insns.def:263 #6 0x1030b55fc in rb_vm_exec vm.c:2585 #7 0x1030fe0ac in rb_iseq_eval_main vm.c:2851 #8 0x102a82588 in rb_ec_exec_node eval.c:281 #9 0x102a81fe0 in ruby_run_node eval.c:319 #10 0x1027f3db4 in rb_main main.c:43 #11 0x1027f3bd4 in main main.c:68 #12 0x183900270 (<unknown module>) 0x606000049528 is located 8 bytes inside of 56-byte region [0x606000049520,0x606000049558) freed by thread T0 here: #0 0x104174d40 in free+0x98 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x54d40) #1 0x102ada89c in rb_gc_impl_free default.c:8183 #2 0x102ada7dc in ruby_sized_xfree gc.c:4507 #3 0x102ac4d34 in ruby_xfree gc.c:4518 #4 0x102f3cb34 in rb_st_free_table st.c:663 #5 0x102bd52d8 in remove_from_constant_cache iseq.c:119 #6 0x102bbe2cc in iseq_clear_ic_references iseq.c:153 #7 0x102bbd2a0 in rb_iseq_free iseq.c:166 #8 0x102b32ed0 in rb_imemo_free imemo.c:564 #9 0x102ac4b44 in rb_gc_obj_free gc.c:1407 #10 0x102af4290 in gc_sweep_plane default.c:3546 #11 0x102af3bdc in gc_sweep_page default.c:3634 #12 0x102aeb140 in gc_sweep_step default.c:3906 #13 0x102aeadf0 in gc_sweep_rest default.c:3978 #14 0x102ae4714 in gc_sweep default.c:4155 #15 0x102af8474 in gc_start default.c:6484 #16 0x102afbe30 in garbage_collect default.c:6363 #17 0x102ad37f0 in rb_gc_impl_start default.c:6816 #18 0x102ad3634 in rb_gc gc.c:3624 #19 0x1031406ec in vm_track_constant_cache vm_insnhelper.c:6342 #20 0x1030b91d8 in vm_ic_track_const_chain vm_insnhelper.c:6356 #21 0x1030b8cf8 in rb_vm_opt_getconstant_path vm_insnhelper.c:6424 #22 0x1030bc1e0 in vm_exec_core insns.def:263 #23 0x1030b55fc in rb_vm_exec vm.c:2585 #24 0x1030fe0ac in rb_iseq_eval_main vm.c:2851 #25 0x102a82588 in rb_ec_exec_node eval.c:281 #26 0x102a81fe0 in ruby_run_node eval.c:319 #27 0x1027f3db4 in rb_main main.c:43 #28 0x1027f3bd4 in main main.c:68 ruby#29 0x183900270 (<unknown module>) previously allocated by thread T0 here: #0 0x104174c04 in malloc+0x94 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x54c04) #1 0x102ada0ec in rb_gc_impl_malloc default.c:8198 #2 0x102acee44 in ruby_xmalloc gc.c:4438 #3 0x102f3c85c in rb_st_init_table_with_size st.c:571 #4 0x102f3c900 in rb_st_init_table st.c:600 #5 0x102f3c920 in rb_st_init_numtable st.c:608 #6 0x103140698 in vm_track_constant_cache vm_insnhelper.c:6337 #7 0x1030b91d8 in vm_ic_track_const_chain vm_insnhelper.c:6356 #8 0x1030b8cf8 in rb_vm_opt_getconstant_path vm_insnhelper.c:6424 #9 0x1030bc1e0 in vm_exec_core insns.def:263 #10 0x1030b55fc in rb_vm_exec vm.c:2585 #11 0x1030fe0ac in rb_iseq_eval_main vm.c:2851 #12 0x102a82588 in rb_ec_exec_node eval.c:281 #13 0x102a81fe0 in ruby_run_node eval.c:319 #14 0x1027f3db4 in rb_main main.c:43 #15 0x1027f3bd4 in main main.c:68 #16 0x183900270 (<unknown module>) This commit fixes this bug by adding a inserting_constant_cache_id field to the VM, which stores the ID that is currently being inserted and, in remove_from_constant_cache, we don't free the ST table for ID equal to this one. Co-Authored-By: Alan Wu <alanwu@ruby-lang.org>
k0kubun
pushed a commit
that referenced
this pull request
Jun 30, 2025
`name` is used via `RSTRING_PTR` within rb_str_catf, which may allocate
and thus potentially trigger GC. Although `name` is still referenced
by a local variable, the compiler might optimize away the reference
before the GC sees it, especially under aggressive optimization or when
debugging tools like ASAN are used.
This patch adds an explicit `RB_GC_GUARD` to ensure `name` is kept alive
until after the last use.
While it's not certain this is the root cause of the following observed
use-after-poison ASAN error, I believe this fix is indeed needed and
hopefully a likely candidate for preventing the error.
```
==1960369==ERROR: AddressSanitizer: use-after-poison on address 0x7ec6a00f1d88 at pc 0x5fb5bcafcf2e bp 0x7ffcc1178cb0 sp 0x7ffcc1178470
READ of size 61 at 0x7ec6a00f1d88 thread T0
#0 0x5fb5bcafcf2d in __asan_memcpy (/tmp/ruby/build/trunk_asan/ruby+0x204f2d) (BuildId: 6d92c84a27b87cfd253c38eeb552593f215ffb3d)
#1 0x5fb5bcde1fa5 in memcpy /usr/include/x86_64-linux-gnu/bits/string_fortified.h:29:10
#2 0x5fb5bcde1fa5 in ruby_nonempty_memcpy /tmp/ruby/src/trunk_asan/include/ruby/internal/memory.h:758:16
#3 0x5fb5bcde1fa5 in ruby__sfvwrite /tmp/ruby/src/trunk_asan/sprintf.c:1083:9
#4 0x5fb5bcde1521 in BSD__sprint /tmp/ruby/src/trunk_asan/vsnprintf.c:318:8
#5 0x5fb5bcde0fbc in BSD_vfprintf /tmp/ruby/src/trunk_asan/vsnprintf.c:1215:3
#6 0x5fb5bcdde4b1 in ruby_vsprintf0 /tmp/ruby/src/trunk_asan/sprintf.c:1164:5
#7 0x5fb5bcddd648 in rb_str_vcatf /tmp/ruby/src/trunk_asan/sprintf.c:1234:5
#8 0x5fb5bcddd648 in rb_str_catf /tmp/ruby/src/trunk_asan/sprintf.c:1245:11
#9 0x5fb5bcf97c67 in location_format /tmp/ruby/src/trunk_asan/vm_backtrace.c:462:9
#10 0x5fb5bcf97c67 in location_to_str /tmp/ruby/src/trunk_asan/vm_backtrace.c:493:12
#11 0x5fb5bcf90a37 in location_to_str_dmyarg /tmp/ruby/src/trunk_asan/vm_backtrace.c:795:12
#12 0x5fb5bcf90a37 in backtrace_collect /tmp/ruby/src/trunk_asan/vm_backtrace.c:786:28
#13 0x5fb5bcf90a37 in backtrace_to_str_ary /tmp/ruby/src/trunk_asan/vm_backtrace.c:804:9
#14 0x5fb5bcf90a37 in rb_backtrace_to_str_ary /tmp/ruby/src/trunk_asan/vm_backtrace.c:816:9
#15 0x5fb5bd335b25 in exc_backtrace /tmp/ruby/src/trunk_asan/error.c:1904:15
#16 0x5fb5bd335b25 in rb_get_backtrace /tmp/ruby/src/trunk_asan/error.c:1924:16
```
https://ci.rvm.jp/results/trunk_asan@ruby-sp1/5810304
k0kubun
pushed a commit
that referenced
this pull request
Aug 26, 2025
If we malloc when the current Ractor is locked, we can deadlock because
GC requires VM lock and Ractor barrier. If another Ractor is waiting on
this Ractor lock, then it will deadlock because the other Ractor will
never join the barrier.
For example, this script deadlocks:
r = Ractor.new do
loop do
Ractor::Port.new
end
end
100000.times do |i|
r.send(nil)
puts i
end
On debug builds, it fails with this assertion error:
vm_sync.c:75: Assertion Failed: vm_lock_enter:cr->sync.locked_by != rb_ractor_self(cr)
On non-debug builds, we can see that it deadlocks in the debugger:
Main Ractor:
frame #3: 0x000000010021fdc4 miniruby`rb_native_mutex_lock(lock=<unavailable>) at thread_pthread.c:115:14
frame #4: 0x0000000100193eb8 miniruby`ractor_send0 [inlined] ractor_lock(r=<unavailable>, file=<unavailable>, line=1180) at ractor.c:73:5
frame #5: 0x0000000100193eb0 miniruby`ractor_send0 [inlined] ractor_send_basket(ec=<unavailable>, rp=0x0000000131092840, b=0x000000011c63de80, raise_on_error=true) at ractor_sync.c:1180:5
frame #6: 0x0000000100193eac miniruby`ractor_send0(ec=<unavailable>, rp=0x0000000131092840, obj=4, move=<unavailable>, raise_on_error=true) at ractor_sync.c:1211:5
Second Ractor:
frame #2: 0x00000001002208d0 miniruby`rb_ractor_sched_barrier_start [inlined] rb_native_cond_wait(cond=<unavailable>, mutex=<unavailable>) at thread_pthread.c:221:13
frame #3: 0x00000001002208cc miniruby`rb_ractor_sched_barrier_start(vm=0x000000013180d600, cr=0x0000000131093460) at thread_pthread.c:1438:13
frame #4: 0x000000010028a328 miniruby`rb_vm_barrier at vm_sync.c:262:13 [artificial]
frame #5: 0x00000001000dfa6c miniruby`gc_start [inlined] rb_gc_vm_barrier at gc.c:179:5
frame #6: 0x00000001000dfa68 miniruby`gc_start [inlined] gc_enter(objspace=0x000000013180fc00, event=gc_enter_event_start, lock_lev=<unavailable>) at default.c:6636:9
frame #7: 0x00000001000dfa48 miniruby`gc_start(objspace=0x000000013180fc00, reason=<unavailable>) at default.c:6361:5
frame #8: 0x00000001000e3fd8 miniruby`objspace_malloc_increase_body [inlined] garbage_collect(objspace=0x000000013180fc00, reason=512) at default.c:6341:15
frame #9: 0x00000001000e3fa4 miniruby`objspace_malloc_increase_body [inlined] garbage_collect_with_gvl(objspace=0x000000013180fc00, reason=512) at default.c:6741:16
frame #10: 0x00000001000e3f88 miniruby`objspace_malloc_increase_body(objspace=0x000000013180fc00, mem=<unavailable>, new_size=<unavailable>, old_size=<unavailable>, type=<unavailable>) at default.c:8007:13
frame #11: 0x00000001000e3c44 miniruby`rb_gc_impl_malloc [inlined] objspace_malloc_fixup(objspace=0x000000013180fc00, mem=0x000000011c700000, size=12582912) at default.c:8085:5
frame #12: 0x00000001000e3c30 miniruby`rb_gc_impl_malloc(objspace_ptr=0x000000013180fc00, size=12582912) at default.c:8182:12
frame #13: 0x00000001000d4584 miniruby`ruby_xmalloc [inlined] ruby_xmalloc_body(size=<unavailable>) at gc.c:5128:12
frame #14: 0x00000001000d4568 miniruby`ruby_xmalloc(size=<unavailable>) at gc.c:5118:34
frame #15: 0x00000001001eb184 miniruby`rb_st_init_existing_table_with_size(tab=0x000000011c2b4b40, type=<unavailable>, size=<unavailable>) at st.c:559:39
frame #16: 0x00000001001ebc74 miniruby`rebuild_table_if_necessary [inlined] rb_st_init_table_with_size(type=0x00000001004f4a78, size=524287) at st.c:585:5
frame #17: 0x00000001001ebc5c miniruby`rebuild_table_if_necessary [inlined] rebuild_table(tab=0x000000013108e2f0) at st.c:753:19
frame #18: 0x00000001001ebbfc miniruby`rebuild_table_if_necessary(tab=0x000000013108e2f0) at st.c:1125:9
frame #19: 0x00000001001eba08 miniruby`rb_st_insert(tab=0x000000013108e2f0, key=262144, value=4767566624) at st.c:1143:5
frame #20: 0x0000000100194b84 miniruby`ractor_port_initialzie [inlined] ractor_add_port(r=0x0000000131093460, id=262144) at ractor_sync.c:399:9
frame #21: 0x0000000100194b58 miniruby`ractor_port_initialzie [inlined] ractor_port_init(rpv=4750065560, r=0x0000000131093460) at ractor_sync.c:87:5
frame #22: 0x0000000100194b34 miniruby`ractor_port_initialzie(self=4750065560) at ractor_sync.c:103:12
k0kubun
pushed a commit
that referenced
this pull request
Oct 8, 2025
Fix use-after-free in constant cache [Bug #20921] When we create a cache entry for a constant, the following sequence of events could happen: - vm_track_constant_cache is called to insert a constant cache. - In vm_track_constant_cache, we first look up the ST table for the ID of the constant. Assume the ST table exists because another iseq also holds a cache entry for this ID. - We then insert into this ST table with the iseq_inline_constant_cache. - However, while inserting into this ST table, it allocates memory, which could trigger a GC. Assume that it does trigger a GC. - The GC frees the one and only other iseq that holds a cache entry for this ID. - In remove_from_constant_cache, it will appear that the ST table is now empty because there are no more iseq with cache entries for this ID, so we free the ST table. - We complete GC and continue our st_insert. However, this ST table has been freed so we now have a use-after-free. This issue is very hard to reproduce, because it requires that the GC runs at a very specific time. However, we can make it show up by applying this patch which runs GC right before the st_insert to mimic the st_insert triggering a GC: diff --git a/vm_insnhelper.c b/vm_insnhelper.c index 3cb23f0..a93998136a 100644 --- a/vm_insnhelper.c +++ b/vm_insnhelper.c @@ -6338,6 +6338,10 @@ vm_track_constant_cache(ID id, void *ic) rb_id_table_insert(const_cache, id, (VALUE)ics); } + if (id == rb_intern("MyConstant")) rb_gc(); + st_insert(ics, (st_data_t) ic, (st_data_t) Qtrue); } And if we run this script: Object.const_set("MyConstant", "Hello!") my_proc = eval("-> { MyConstant }") my_proc.call my_proc = eval("-> { MyConstant }") my_proc.call We can see that ASAN outputs a use-after-free error: ==36540==ERROR: AddressSanitizer: heap-use-after-free on address 0x606000049528 at pc 0x000102f3ceac bp 0x00016d607a70 sp 0x00016d607a68 READ of size 8 at 0x606000049528 thread T0 #0 0x102f3cea8 in do_hash st.c:321 #1 0x102f3ddd0 in rb_st_insert st.c:1132 #2 0x103140700 in vm_track_constant_cache vm_insnhelper.c:6345 #3 0x1030b91d8 in vm_ic_track_const_chain vm_insnhelper.c:6356 #4 0x1030b8cf8 in rb_vm_opt_getconstant_path vm_insnhelper.c:6424 #5 0x1030bc1e0 in vm_exec_core insns.def:263 #6 0x1030b55fc in rb_vm_exec vm.c:2585 #7 0x1030fe0ac in rb_iseq_eval_main vm.c:2851 #8 0x102a82588 in rb_ec_exec_node eval.c:281 #9 0x102a81fe0 in ruby_run_node eval.c:319 #10 0x1027f3db4 in rb_main main.c:43 #11 0x1027f3bd4 in main main.c:68 #12 0x183900270 (<unknown module>) 0x606000049528 is located 8 bytes inside of 56-byte region [0x606000049520,0x606000049558) freed by thread T0 here: #0 0x104174d40 in free+0x98 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x54d40) #1 0x102ada89c in rb_gc_impl_free default.c:8183 #2 0x102ada7dc in ruby_sized_xfree gc.c:4507 #3 0x102ac4d34 in ruby_xfree gc.c:4518 #4 0x102f3cb34 in rb_st_free_table st.c:663 #5 0x102bd52d8 in remove_from_constant_cache iseq.c:119 #6 0x102bbe2cc in iseq_clear_ic_references iseq.c:153 #7 0x102bbd2a0 in rb_iseq_free iseq.c:166 #8 0x102b32ed0 in rb_imemo_free imemo.c:564 #9 0x102ac4b44 in rb_gc_obj_free gc.c:1407 #10 0x102af4290 in gc_sweep_plane default.c:3546 #11 0x102af3bdc in gc_sweep_page default.c:3634 #12 0x102aeb140 in gc_sweep_step default.c:3906 #13 0x102aeadf0 in gc_sweep_rest default.c:3978 #14 0x102ae4714 in gc_sweep default.c:4155 #15 0x102af8474 in gc_start default.c:6484 #16 0x102afbe30 in garbage_collect default.c:6363 #17 0x102ad37f0 in rb_gc_impl_start default.c:6816 #18 0x102ad3634 in rb_gc gc.c:3624 #19 0x1031406ec in vm_track_constant_cache vm_insnhelper.c:6342 #20 0x1030b91d8 in vm_ic_track_const_chain vm_insnhelper.c:6356 #21 0x1030b8cf8 in rb_vm_opt_getconstant_path vm_insnhelper.c:6424 #22 0x1030bc1e0 in vm_exec_core insns.def:263 #23 0x1030b55fc in rb_vm_exec vm.c:2585 #24 0x1030fe0ac in rb_iseq_eval_main vm.c:2851 #25 0x102a82588 in rb_ec_exec_node eval.c:281 #26 0x102a81fe0 in ruby_run_node eval.c:319 #27 0x1027f3db4 in rb_main main.c:43 #28 0x1027f3bd4 in main main.c:68 ruby#29 0x183900270 (<unknown module>) previously allocated by thread T0 here: #0 0x104174c04 in malloc+0x94 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x54c04) #1 0x102ada0ec in rb_gc_impl_malloc default.c:8198 #2 0x102acee44 in ruby_xmalloc gc.c:4438 #3 0x102f3c85c in rb_st_init_table_with_size st.c:571 #4 0x102f3c900 in rb_st_init_table st.c:600 #5 0x102f3c920 in rb_st_init_numtable st.c:608 #6 0x103140698 in vm_track_constant_cache vm_insnhelper.c:6337 #7 0x1030b91d8 in vm_ic_track_const_chain vm_insnhelper.c:6356 #8 0x1030b8cf8 in rb_vm_opt_getconstant_path vm_insnhelper.c:6424 #9 0x1030bc1e0 in vm_exec_core insns.def:263 #10 0x1030b55fc in rb_vm_exec vm.c:2585 #11 0x1030fe0ac in rb_iseq_eval_main vm.c:2851 #12 0x102a82588 in rb_ec_exec_node eval.c:281 #13 0x102a81fe0 in ruby_run_node eval.c:319 #14 0x1027f3db4 in rb_main main.c:43 #15 0x1027f3bd4 in main main.c:68 #16 0x183900270 (<unknown module>) This commit fixes this bug by adding a inserting_constant_cache_id field to the VM, which stores the ID that is currently being inserted and, in remove_from_constant_cache, we don't free the ST table for ID equal to this one. Co-Authored-By: Alan Wu <alanwu@ruby-lang.org>
k0kubun
pushed a commit
that referenced
this pull request
Nov 6, 2025
We were seeing errors like: ``` * thread #8, stop reason = EXC_BAD_ACCESS (code=1, address=0x803) * frame #0: 0x00000001001fe944 ruby`rb_st_lookup(tab=0x00000000000007fb, key=1, value=0x00000001305b7490) at st.c:1066:22 frame #1: 0x000000010002d658 ruby`remove_class_from_subclasses [inlined] class_get_subclasses_for_ns(tbl=0x00000000000007fb, ns_id=1) at class.c:604:9 frame #2: 0x000000010002d650 ruby`remove_class_from_subclasses(tbl=0x00000000000007fb, ns_id=1, klass=4754039232) at class.c:620:34 frame #3: 0x000000010002c8a8 ruby`rb_class_classext_free_subclasses(ext=0x000000011b5ce1d8, klass=4754039232, replacing=<unavailable>) at class.c:700:9 frame #4: 0x000000010002c760 ruby`rb_class_classext_free(klass=4754039232, ext=0x000000011b5ce1d8, is_prime=true) at class.c:105:5 frame #5: 0x00000001000e770c ruby`classext_free(ext=<unavailable>, is_prime=<unavailable>, namespace=<unavailable>, arg=<unavailable>) at gc.c:1231:5 [artificial] frame #6: 0x000000010002d178 ruby`rb_class_classext_foreach(klass=<unavailable>, func=(ruby`classext_free at gc.c:1228), arg=0x00000001305b75c0) at class.c:518:5 frame #7: 0x00000001000e745c ruby`rb_gc_obj_free(objspace=0x000000012500c400, obj=4754039232) at gc.c:1282:9 frame #8: 0x00000001000e70d4 ruby`gc_sweep_plane(objspace=0x000000012500c400, heap=<unavailable>, p=4754039232, bitset=4095, ctx=0x00000001305b76e8) at default.c:3482:21 frame #9: 0x00000001000e6e9c ruby`gc_sweep_page(objspace=0x000000012500c400, heap=0x000000012500c540, ctx=0x00000001305b76e8) at default.c:3567:13 frame #10: 0x00000001000e51d0 ruby`gc_sweep_step(objspace=0x000000012500c400, heap=0x000000012500c540) at default.c:3848:9 frame #11: 0x00000001000e1880 ruby`gc_continue [inlined] gc_sweep_continue(objspace=0x000000012500c400, sweep_heap=0x000000012500c540) at default.c:3931:13 frame #12: 0x00000001000e1754 ruby`gc_continue(objspace=0x000000012500c400, heap=0x000000012500c540) at default.c:2037:9 frame #13: 0x00000001000e10bc ruby`newobj_cache_miss [inlined] heap_prepare(objspace=0x000000012500c400, heap=0x000000012500c540) at default.c:2056:5 frame #14: 0x00000001000e1074 ruby`newobj_cache_miss [inlined] heap_next_free_page(objspace=0x000000012500c400, heap=0x000000012500c540) at default.c:2280:9 frame #15: 0x00000001000e106c ruby`newobj_cache_miss(objspace=0x000000012500c400, cache=0x0000600001b00300, heap_idx=2, vm_locked=false) at default.c:2387:38 frame #16: 0x00000001000e0d28 ruby`newobj_alloc(objspace=<unavailable>, cache=<unavailable>, heap_idx=<unavailable>, vm_locked=<unavailable>) at default.c:2411:15 [artificial] frame #17: 0x00000001000d7214 ruby`newobj_of [inlined] rb_gc_impl_new_obj(objspace_ptr=<unavailable>, cache_ptr=<unavailable>, klass=<unavailable>, flags=<unavailable>, wb_protected=<unavailable>, alloc_size=<unavailable>) at default.c:2490:15 frame #18: 0x00000001000d719c ruby`newobj_of(cr=<unavailable>, klass=4313971728, flags=258, wb_protected=<unavailable>, size=<unavailable>) at gc.c:995:17 frame #19: 0x00000001000d73ec ruby`rb_wb_protected_newobj_of(ec=<unavailable>, klass=<unavailable>, flags=<unavailable>, size=<unavailable>) at gc.c:1044:12 [artificial] frame #20: 0x0000000100032d34 ruby`class_alloc0(type=<unavailable>, klass=4313971728, namespaceable=<unavailable>) at class.c:803:5 ```
k0kubun
pushed a commit
that referenced
this pull request
Nov 11, 2025
We don't decrement the super and module subclasses count for iclasses that
are having their classext replaced. This causes the reference count to be
incorrect and leak memory.
The following script demonstrates the memory leak:
module Foo
refine(Object) do
define_method(:<=) {}
end
end
class Bar
include Comparable
end
With RUBY_FREE_AT_EXIT and ASAN, we can see many memory leaks, including:
Direct leak of 16 byte(s) in 1 object(s) allocated from:
#0 0x599f715adca2 in calloc (miniruby+0x64ca2)
#1 0x599f716bd779 in calloc1 gc/default/default.c:1495:12
#2 0x599f716d1370 in rb_gc_impl_calloc gc/default/default.c:8216:5
#3 0x599f716b8ab1 in ruby_xcalloc_body gc.c:5221:12
#4 0x599f716b269c in ruby_xcalloc gc.c:5215:34
#5 0x599f715eab23 in class_alloc0 class.c:790:22
#6 0x599f715e4bec in class_alloc class.c:836:12
#7 0x599f715e60c9 in module_new class.c:1693:17
#8 0x599f715e60a2 in rb_module_new class.c:1701:12
#9 0x599f715e6303 in rb_define_module class.c:1733:14
#10 0x599f715ebc5f in Init_Comparable compar.c:315:22
#11 0x599f716e35f5 in rb_call_inits inits.c:32:5
#12 0x599f7169cbfd in ruby_setup eval.c:88:9
#13 0x599f7169cdac in ruby_init eval.c:100:17
#14 0x599f715b0fa9 in rb_main main.c:41:5
#15 0x599f715b0f59 in main main.c:62:12
#16 0x739b2f02a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#17 0x739b2f02a28a in __libc_start_main csu/../csu/libc-start.c:360:3
#18 0x599f7157c424 in _start (miniruby+0x33424)
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