[ruby-core:112958] [Ruby master Bug#19320] Crash during compaction while traversing the stack

Issue #19320 has been updated by nagachika (Tomoyuki Chikanaga).

Backport changed from 2.7: DONTNEED, 3.0: REQUIRED, 3.1: REQUIRED, 3.2: DONE to 2.7: DONTNEED, 3.0: REQUIRED, 3.1: DONE, 3.2: DONE

ruby_3_1 8322413e58bdce11136c33aec3e0611b2b135cd8 merged revision(s) 72eb33066fa9e7dacb7470cd140b219abe37667e.

----------------------------------------
Bug #19320: Crash during compaction while traversing the stack
https://bugs.ruby-lang.org/issues/19320#change-102485

* Author: peterzhu2118 (Peter Zhu)
* Status: Closed
* Priority: Normal
* Backport: 2.7: DONTNEED, 3.0: REQUIRED, 3.1: DONE, 3.2: DONE
----------------------------------------
Fix PR: https://github.com/ruby/ruby/pull/7081

Applying the following patch to test/erb/test_erb.rb and running that file will cause Ruby to crash on my machine (macOS 13.1 on M1 Pro):

```diff
--- a/test/erb/test_erb.rb
+++ b/test/erb/test_erb.rb
@@ -7,6 +7,12 @@
 class TestERB < Test::Unit::TestCase
   class MyError < RuntimeError ; end

+  def setup
+    GC.auto_compact = true
+    GC.stress = true
+    GC.verify_compaction_references(expand_heap: true, toward: :empty)
+  end
+
```

It crashes with the following log:

```
/Users/peter/src/ruby/lib/erb/compiler.rb:276: [BUG] Segmentation fault at 0x00000001083a8690
...
-- C level backtrace information -------------------------------------------
...
/Users/peter/src/ruby/build/ruby(rb_vm_each_stack_value+0xa8) [0x104cc3a44] ../vm.c:2737
/Users/peter/src/ruby/build/ruby(rb_vm_each_stack_value+0xa8) [0x104cc3a44] ../vm.c:2737
/Users/peter/src/ruby/build/ruby(check_stack_for_moved+0x2c) [0x104b272a4] ../gc.c:5512
/Users/peter/src/ruby/build/ruby(gc_compact_finish) ../gc.c:5534
/Users/peter/src/ruby/build/ruby(gc_sweep_compact) ../gc.c:8653
/Users/peter/src/ruby/build/ruby(gc_sweep) ../gc.c:6196
/Users/peter/src/ruby/build/ruby(has_sweeping_pages+0x0) [0x104b19c54] ../gc.c:9568
/Users/peter/src/ruby/build/ruby(gc_rest) ../gc.c:9570
```

This crash happens because it's reading the VALUE at sp. But since sp points to the top of the stack, it's reading the VALUE above the top of the stack, which is causing this segfault.

I can repro this crash in Ruby 3.2.0, but looking at the code I think it can happen in Ruby 3.1 and 3.0 as well.




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