ruby.git/weakmap.c, branch v3_3_11

merge revision(s) 91a10c07579f282a94e4b5830feaeca87f9a7dd3: [Backport #21112]

2025-03-08T09:21:16+00:00

	Fix a typo in WeakKeyMap argument error

	[Bug #21112]

[Backport 3.3] [Bug #20691] Fix use-after-free in WeakKeyMap#clear (#11443)

2024-08-23T22:48:08+00:00

Fix use-after-free in WeakKeyMap#clear

[Bug #20691]

If the WeakKeyMap has been marked but sweeping hasn't started yet and we
cann WeakKeyMap#clear, then there could be a use-after-free because we do
not call rb_gc_remove_weak to remove the key from the GC.

For example, the following code triggers use-after-free errors in Valgrind:

    map = ObjectSpace::WeakKeyMap.new

    1_000.times do
      1_000.times do
        map[Object.new] = nil
      end

      map.clear
    end

Output from Valgrind:

    ==61230== Invalid read of size 8
    ==61230==    at 0x25CAF8: gc_update_weak_references (default.c:5593)
    ==61230==    by 0x25CAF8: gc_marks_finish (default.c:5641)
    ==61230==    by 0x26031C: gc_marks_continue (default.c:5987)
    ==61230==    by 0x26031C: gc_continue (default.c:2255)
    ==61230==    by 0x2605FC: newobj_cache_miss (default.c:2589)
    ==61230==    by 0x26111F: newobj_alloc (default.c:2622)
    ==61230==    by 0x26111F: rb_gc_impl_new_obj (default.c:2701)
    ==61230==    by 0x26111F: newobj_of (gc.c:890)
    ==61230==    by 0x26111F: rb_wb_protected_newobj_of (gc.c:917)
    ==61230==    by 0x2DE218: rb_class_allocate_instance (object.c:131)
    ==61230==    by 0x2E32A8: class_call_alloc_func (object.c:2141)
    ==61230==    by 0x2E32A8: rb_class_alloc (object.c:2113)
    ==61230==    by 0x2E32A8: rb_class_new_instance_pass_kw (object.c:2172)
    ==61230==    by 0x4296BC: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3788)
    ==61230==    by 0x44A9CD: vm_sendish (vm_insnhelper.c:5955)
    ==61230==    by 0x44A9CD: vm_exec_core (insns.def:898)
    ==61230==    by 0x43A0E4: rb_vm_exec (vm.c:2564)
    ==61230==    by 0x2341B4: rb_ec_exec_node (eval.c:281)
    ==61230==    by 0x236258: ruby_run_node (eval.c:319)
    ==61230==    by 0x15D665: rb_main (main.c:43)
    ==61230==    by 0x15D665: main (main.c:62)
    ==61230==  Address 0x2159cb00 is 0 bytes inside a block of size 8 free'd
    ==61230==    at 0x4849B2C: free (vg_replace_malloc.c:989)
    ==61230==    by 0x248EF1: rb_gc_impl_free (default.c:8512)
    ==61230==    by 0x248EF1: rb_gc_impl_free (default.c:8493)
    ==61230==    by 0x248EF1: ruby_sized_xfree.constprop.0 (gc.c:4178)
    ==61230==    by 0x4627EC: wkmap_free_table_i (weakmap.c:652)
    ==61230==    by 0x3A54AF: apply_functor (st.c:1633)
    ==61230==    by 0x3A54AF: st_general_foreach (st.c:1543)
    ==61230==    by 0x3A54AF: rb_st_foreach (st.c:1640)
    ==61230==    by 0x46203C: wkmap_clear (weakmap.c:973)
    ==61230==    by 0x4296BC: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3788)
    ==61230==    by 0x44A9CD: vm_sendish (vm_insnhelper.c:5955)
    ==61230==    by 0x44A9CD: vm_exec_core (insns.def:898)
    ==61230==    by 0x43A0E4: rb_vm_exec (vm.c:2564)
    ==61230==    by 0x2341B4: rb_ec_exec_node (eval.c:281)
    ==61230==    by 0x236258: ruby_run_node (eval.c:319)
    ==61230==    by 0x15D665: rb_main (main.c:43)
    ==61230==    by 0x15D665: main (main.c:62)
    ==61230==  Block was alloc'd at
    ==61230==    at 0x484680F: malloc (vg_replace_malloc.c:446)
    ==61230==    by 0x25C68E: rb_gc_impl_malloc (default.c:8527)
    ==61230==    by 0x4622E9: wkmap_aset_replace (weakmap.c:817)
    ==61230==    by 0x3A4D02: rb_st_update (st.c:1487)
    ==61230==    by 0x4623E4: wkmap_aset (weakmap.c:854)
    ==61230==    by 0x4296BC: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3788)
    ==61230==    by 0x44A9CD: vm_sendish (vm_insnhelper.c:5955)
    ==61230==    by 0x44A9CD: vm_exec_core (insns.def:898)
    ==61230==    by 0x43A0E4: rb_vm_exec (vm.c:2564)
    ==61230==    by 0x2341B4: rb_ec_exec_node (eval.c:281)
    ==61230==    by 0x236258: ruby_run_node (eval.c:319)
    ==61230==    by 0x15D665: rb_main (main.c:43)
    ==61230==    by 0x15D665: main (main.c:62)
    ==61230==
    ==61230== Invalid write of size 8
    ==61230==    at 0x25CB3B: gc_update_weak_references (default.c:5598)
    ==61230==    by 0x25CB3B: gc_marks_finish (default.c:5641)
    ==61230==    by 0x26031C: gc_marks_continue (default.c:5987)
    ==61230==    by 0x26031C: gc_continue (default.c:2255)
    ==61230==    by 0x2605FC: newobj_cache_miss (default.c:2589)
    ==61230==    by 0x26111F: newobj_alloc (default.c:2622)
    ==61230==    by 0x26111F: rb_gc_impl_new_obj (default.c:2701)
    ==61230==    by 0x26111F: newobj_of (gc.c:890)
    ==61230==    by 0x26111F: rb_wb_protected_newobj_of (gc.c:917)
    ==61230==    by 0x2DE218: rb_class_allocate_instance (object.c:131)
    ==61230==    by 0x2E32A8: class_call_alloc_func (object.c:2141)
    ==61230==    by 0x2E32A8: rb_class_alloc (object.c:2113)
    ==61230==    by 0x2E32A8: rb_class_new_instance_pass_kw (object.c:2172)
    ==61230==    by 0x4296BC: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3788)
    ==61230==    by 0x44A9CD: vm_sendish (vm_insnhelper.c:5955)
    ==61230==    by 0x44A9CD: vm_exec_core (insns.def:898)
    ==61230==    by 0x43A0E4: rb_vm_exec (vm.c:2564)
    ==61230==    by 0x2341B4: rb_ec_exec_node (eval.c:281)
    ==61230==    by 0x236258: ruby_run_node (eval.c:319)
    ==61230==    by 0x15D665: rb_main (main.c:43)
    ==61230==    by 0x15D665: main (main.c:62)
    ==61230==  Address 0x2159cb00 is 0 bytes inside a block of size 8 free'd
    ==61230==    at 0x4849B2C: free (vg_replace_malloc.c:989)
    ==61230==    by 0x248EF1: rb_gc_impl_free (default.c:8512)
    ==61230==    by 0x248EF1: rb_gc_impl_free (default.c:8493)
    ==61230==    by 0x248EF1: ruby_sized_xfree.constprop.0 (gc.c:4178)
    ==61230==    by 0x4627EC: wkmap_free_table_i (weakmap.c:652)
    ==61230==    by 0x3A54AF: apply_functor (st.c:1633)
    ==61230==    by 0x3A54AF: st_general_foreach (st.c:1543)
    ==61230==    by 0x3A54AF: rb_st_foreach (st.c:1640)
    ==61230==    by 0x46203C: wkmap_clear (weakmap.c:973)
    ==61230==    by 0x4296BC: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3788)
    ==61230==    by 0x44A9CD: vm_sendish (vm_insnhelper.c:5955)
    ==61230==    by 0x44A9CD: vm_exec_core (insns.def:898)
    ==61230==    by 0x43A0E4: rb_vm_exec (vm.c:2564)
    ==61230==    by 0x2341B4: rb_ec_exec_node (eval.c:281)
    ==61230==    by 0x236258: ruby_run_node (eval.c:319)
    ==61230==    by 0x15D665: rb_main (main.c:43)
    ==61230==    by 0x15D665: main (main.c:62)
    ==61230==  Block was alloc'd at
    ==61230==    at 0x484680F: malloc (vg_replace_malloc.c:446)
    ==61230==    by 0x25C68E: rb_gc_impl_malloc (default.c:8527)
    ==61230==    by 0x4622E9: wkmap_aset_replace (weakmap.c:817)
    ==61230==    by 0x3A4D02: rb_st_update (st.c:1487)
    ==61230==    by 0x4623E4: wkmap_aset (weakmap.c:854)
    ==61230==    by 0x4296BC: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3788)
    ==61230==    by 0x44A9CD: vm_sendish (vm_insnhelper.c:5955)
    ==61230==    by 0x44A9CD: vm_exec_core (insns.def:898)
    ==61230==    by 0x43A0E4: rb_vm_exec (vm.c:2564)
    ==61230==    by 0x2341B4: rb_ec_exec_node (eval.c:281)
    ==61230==    by 0x236258: ruby_run_node (eval.c:319)
    ==61230==    by 0x15D665: rb_main (main.c:43)
    ==61230==    by 0x15D665: main (main.c:62)

Co-authored-by: Jean Boussier

[Backport 3.3] [Bug #20688] Fix use-after-free for WeakMap and WeakKeyMap (#11439)

2024-08-22T22:54:55+00:00

* Add struct weakmap_entry for WeakMap entries

* Refactor wmap_foreach to pass weakmap_entry

* Use wmap_foreach for wmap_mark

* Refactor wmap_compact to use wmap_foreach

* Remove wmap_free_entry

* Fix WeakMap use-after-free

[Bug #20688]

We cannot free the weakmap_entry before the ST_DELETE because it could
hash the key which would read the weakmap_entry and would cause a
use-after-free. Instead, we store the entry and free it on the next
iteration.

For example, the following script triggers a use-after-free in Valgrind:

    weakmap = ObjectSpace::WeakMap.new
    10_000.times { weakmap[Object.new] = Object.new }

    ==25795== Invalid read of size 8
    ==25795==    at 0x462297: wmap_cmp (weakmap.c:165)
    ==25795==    by 0x3A2B1C: find_table_bin_ind (st.c:930)
    ==25795==    by 0x3A5EAA: st_general_foreach (st.c:1599)
    ==25795==    by 0x3A5EAA: rb_st_foreach (st.c:1640)
    ==25795==    by 0x25C991: gc_mark_children (default.c:4870)
    ==25795==    by 0x25C991: gc_marks_wb_unprotected_objects_plane (default.c:5565)
    ==25795==    by 0x25C991: rgengc_rememberset_mark_plane (default.c:5557)
    ==25795==    by 0x25C991: rgengc_rememberset_mark (default.c:6233)
    ==25795==    by 0x25C991: gc_marks_start (default.c:6057)
    ==25795==    by 0x25C991: gc_marks (default.c:6077)
    ==25795==    by 0x25C991: gc_start (default.c:6723)
    ==25795==    by 0x260F96: heap_prepare (default.c:2282)
    ==25795==    by 0x260F96: heap_next_free_page (default.c:2489)
    ==25795==    by 0x260F96: newobj_cache_miss (default.c:2598)
    ==25795==    by 0x26197F: newobj_alloc (default.c:2622)
    ==25795==    by 0x26197F: rb_gc_impl_new_obj (default.c:2701)
    ==25795==    by 0x26197F: newobj_of (gc.c:890)
    ==25795==    by 0x26197F: rb_wb_protected_newobj_of (gc.c:917)
    ==25795==    by 0x2DEA88: rb_class_allocate_instance (object.c:131)
    ==25795==    by 0x2E3B18: class_call_alloc_func (object.c:2141)
    ==25795==    by 0x2E3B18: rb_class_alloc (object.c:2113)
    ==25795==    by 0x2E3B18: rb_class_new_instance_pass_kw (object.c:2172)
    ==25795==    by 0x429DDC: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3786)
    ==25795==    by 0x44B08D: vm_sendish (vm_insnhelper.c:5953)
    ==25795==    by 0x44B08D: vm_exec_core (insns.def:898)
    ==25795==    by 0x43A7A4: rb_vm_exec (vm.c:2564)
    ==25795==    by 0x234914: rb_ec_exec_node (eval.c:281)
    ==25795==  Address 0x21603710 is 0 bytes inside a block of size 16 free'd
    ==25795==    at 0x4849B2C: free (vg_replace_malloc.c:989)
    ==25795==    by 0x249651: rb_gc_impl_free (default.c:8527)
    ==25795==    by 0x249651: rb_gc_impl_free (default.c:8508)
    ==25795==    by 0x249651: ruby_sized_xfree.constprop.0 (gc.c:4178)
    ==25795==    by 0x4626EC: ruby_sized_xfree_inlined (gc.h:277)
    ==25795==    by 0x4626EC: wmap_free_entry (weakmap.c:45)
    ==25795==    by 0x4626EC: wmap_mark_weak_table_i (weakmap.c:61)
    ==25795==    by 0x3A5CEF: apply_functor (st.c:1633)
    ==25795==    by 0x3A5CEF: st_general_foreach (st.c:1543)
    ==25795==    by 0x3A5CEF: rb_st_foreach (st.c:1640)
    ==25795==    by 0x25C991: gc_mark_children (default.c:4870)
    ==25795==    by 0x25C991: gc_marks_wb_unprotected_objects_plane (default.c:5565)
    ==25795==    by 0x25C991: rgengc_rememberset_mark_plane (default.c:5557)
    ==25795==    by 0x25C991: rgengc_rememberset_mark (default.c:6233)
    ==25795==    by 0x25C991: gc_marks_start (default.c:6057)
    ==25795==    by 0x25C991: gc_marks (default.c:6077)
    ==25795==    by 0x25C991: gc_start (default.c:6723)
    ==25795==    by 0x260F96: heap_prepare (default.c:2282)
    ==25795==    by 0x260F96: heap_next_free_page (default.c:2489)
    ==25795==    by 0x260F96: newobj_cache_miss (default.c:2598)
    ==25795==    by 0x26197F: newobj_alloc (default.c:2622)
    ==25795==    by 0x26197F: rb_gc_impl_new_obj (default.c:2701)
    ==25795==    by 0x26197F: newobj_of (gc.c:890)
    ==25795==    by 0x26197F: rb_wb_protected_newobj_of (gc.c:917)
    ==25795==    by 0x2DEA88: rb_class_allocate_instance (object.c:131)
    ==25795==    by 0x2E3B18: class_call_alloc_func (object.c:2141)
    ==25795==    by 0x2E3B18: rb_class_alloc (object.c:2113)
    ==25795==    by 0x2E3B18: rb_class_new_instance_pass_kw (object.c:2172)
    ==25795==    by 0x429DDC: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3786)
    ==25795==    by 0x44B08D: vm_sendish (vm_insnhelper.c:5953)
    ==25795==    by 0x44B08D: vm_exec_core (insns.def:898)
    ==25795==    by 0x43A7A4: rb_vm_exec (vm.c:2564)
    ==25795==  Block was alloc'd at
    ==25795==    at 0x484680F: malloc (vg_replace_malloc.c:446)
    ==25795==    by 0x25CE9E: rb_gc_impl_malloc (default.c:8542)
    ==25795==    by 0x462A39: wmap_aset_replace (weakmap.c:423)
    ==25795==    by 0x3A5542: rb_st_update (st.c:1487)
    ==25795==    by 0x462B8E: wmap_aset (weakmap.c:452)
    ==25795==    by 0x429DDC: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3786)
    ==25795==    by 0x44B08D: vm_sendish (vm_insnhelper.c:5953)
    ==25795==    by 0x44B08D: vm_exec_core (insns.def:898)
    ==25795==    by 0x43A7A4: rb_vm_exec (vm.c:2564)
    ==25795==    by 0x234914: rb_ec_exec_node (eval.c:281)
    ==25795==    by 0x2369B8: ruby_run_node (eval.c:319)
    ==25795==    by 0x15D675: rb_main (main.c:43)
    ==25795==    by 0x15D675: main (main.c:62)

* Fix use-after-free for WeakKeyMap

[Bug #20688]

We cannot free the key before the ST_DELETE because it could hash the
key which would read the key and would cause a use-after-free. Instead,
we store the key and free it on the next iteration.

[DOC] Enhance docs for WeakMap and WeakKeyMap (#9160)

2023-12-14T21:33:33+00:00

Enhance docs for WeakMap and WeakKeyMap

* WeakKeyMap: more class-level explanations, more details
  on #getkey, fix a slight bug in code of #delete example;
* WeekMap: a bit more detailed class- and method-level docs.

Make WeakKeyMap safe for compaction during allocation

2023-12-12T14:01:21+00:00

During allocation, the table may not have been allocated yet which would
crash in the st_foreach.

Make WeakMap safe for compaction during allocation

2023-12-12T14:01:21+00:00

During allocation, the table may not have been allocated yet which would
crash in the st_foreach.

Implement WeakKeyMap on VWA

2023-11-21T20:17:25+00:00

Benchmark:

```
puts(Benchmark.measure do
  10_000_000.times do
    ObjectSpace::WeakKeyMap.new
  end
end)
```

Before:

```
2.554772   0.014167   2.568939 (  2.575763)
```

After:

```
1.994920   0.013583   2.008503 (  2.012139)
```

Implement WeakMap on VWA

2023-11-21T20:17:25+00:00

Benchmark:

```
puts(Benchmark.measure do
  10_000_000.times do
    ObjectSpace::WeakMap.new
  end
end)
```

Before:

```
2.568662   0.014001   2.582663 (  2.601743)
```

After:

```
2.025523   0.008676   2.034199 (  2.041760)
```

Fix crash in WeakMap during compaction

2023-09-06T18:20:23+00:00

WeakMap can crash during compaction because the st_insert could allocate
memory.

Introduce rb_gc_remove_weak

2023-09-05T18:32:15+00:00

If we're during incremental marking, then Ruby code can execute that
deallocates certain memory buffers that have been called with
rb_gc_mark_weak, which can cause use-after-free bugs.