Select Similar Face Regions triggers AddressSanitizer crash #89247

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System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 446.14

Blender Version
Broken: version: 3.0.0 Alpha, branch: master. Commit hash: ed4222258e
Worked: Haven't built older versions with ASan yet

Short description of error
Selecting similar faces, by face region, causes AddressSanitizer to crash Blender. It detects a buffer overflow.

Exact steps for others to reproduce the error

In a build of Blender that includes AddressSanitizer, go into edit mode on the default cube
Select at least two faces
Hit F3 and type "select face regions"
Run the operator
Crash

This does not cause a crash without AddressSanitizer being present.

Here's the ASan output:

ERROR: AddressSanitizer: dynamic-stack-buffer-overflow on address 0x7ffeefbfa998 at pc 0x000103eb58cd bp 0x7ffeefbfa030 sp 0x7ffeefbfa028
READ of size 4 at 0x7ffeefbfa998 thread T0
    - 0 bm_face_len_cmp source/blender/bmesh/tools/bmesh_region_match.c:558:11
    - 1 wrap_qsort (/Users/ankitkumar/apps/usr/lib/clang/13.0.0/lib/darwin/libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x3e0e9)
    - 2 bm_uuidwalk_init_from_edge source/blender/bmesh/tools/bmesh_region_match.c:583:3
    - 3 bm_mesh_region_match_pair source/blender/bmesh/tools/bmesh_region_match.c:747:7
    - 4 BM_mesh_region_match source/blender/bmesh/tools/bmesh_region_match.c:1433:20
    - 5 edbm_select_similar_region_exec source/blender/editors/mesh/editmesh_select.c:1316:11
    - 6 wm_operator_invoke source/blender/windowmanager/intern/wm_event_system.c:1362:16
    - 7 wm_operator_call_internal source/blender/windowmanager/intern/wm_event_system.c:1557:18
    - 8 WM_operator_name_call_ptr source/blender/windowmanager/intern/wm_event_system.c:1605:10
    - 9 menu_search_exec_fn source/blender/editors/interface/interface_template_search_menu.c:958:7
    - 10 ui_apply_but_funcs_after source/blender/editors/interface/interface_handlers.c:973:7
    - 11 ui_popup_handler source/blender/editors/interface/interface_handlers.c:11121:3
    - 12 wm_handler_ui_call source/blender/windowmanager/intern/wm_event_system.c:693:16
    - 13 wm_handlers_do_intern source/blender/windowmanager/intern/wm_event_system.c:2842:21
    - 14 wm_handlers_do source/blender/windowmanager/intern/wm_event_system.c:2958:16
    - 15 wm_event_do_handlers source/blender/windowmanager/intern/wm_event_system.c:3378:17
    - 16 WM_main source/blender/windowmanager/intern/wm.c:647:5
    - 17 main source/creator/creator.c:519:5
    #18 start (/usr/lib/system/libdyld.dylib:x86_64+0x163d4)

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 446.14 **Blender Version** Broken: version: 3.0.0 Alpha, branch: master. Commit hash: ed4222258ea6fff51c17a2e244b497f03a8e0162 Worked: Haven't built older versions with ASan yet **Short description of error** Selecting similar faces, by face region, causes AddressSanitizer to crash Blender. It detects a buffer overflow. **Exact steps for others to reproduce the error** 1. In a build of Blender that includes AddressSanitizer, go into edit mode on the default cube 2. Select at least two faces 3. Hit F3 and type "select face regions" 4. Run the operator 5. Crash This does not cause a crash without AddressSanitizer being present. Here's the ASan output: ``` ERROR: AddressSanitizer: dynamic-stack-buffer-overflow on address 0x7ffeefbfa998 at pc 0x000103eb58cd bp 0x7ffeefbfa030 sp 0x7ffeefbfa028 READ of size 4 at 0x7ffeefbfa998 thread T0 - 0 bm_face_len_cmp source/blender/bmesh/tools/bmesh_region_match.c:558:11 - 1 wrap_qsort (/Users/ankitkumar/apps/usr/lib/clang/13.0.0/lib/darwin/libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x3e0e9) - 2 bm_uuidwalk_init_from_edge source/blender/bmesh/tools/bmesh_region_match.c:583:3 - 3 bm_mesh_region_match_pair source/blender/bmesh/tools/bmesh_region_match.c:747:7 - 4 BM_mesh_region_match source/blender/bmesh/tools/bmesh_region_match.c:1433:20 - 5 edbm_select_similar_region_exec source/blender/editors/mesh/editmesh_select.c:1316:11 - 6 wm_operator_invoke source/blender/windowmanager/intern/wm_event_system.c:1362:16 - 7 wm_operator_call_internal source/blender/windowmanager/intern/wm_event_system.c:1557:18 - 8 WM_operator_name_call_ptr source/blender/windowmanager/intern/wm_event_system.c:1605:10 - 9 menu_search_exec_fn source/blender/editors/interface/interface_template_search_menu.c:958:7 - 10 ui_apply_but_funcs_after source/blender/editors/interface/interface_handlers.c:973:7 - 11 ui_popup_handler source/blender/editors/interface/interface_handlers.c:11121:3 - 12 wm_handler_ui_call source/blender/windowmanager/intern/wm_event_system.c:693:16 - 13 wm_handlers_do_intern source/blender/windowmanager/intern/wm_event_system.c:2842:21 - 14 wm_handlers_do source/blender/windowmanager/intern/wm_event_system.c:2958:16 - 15 wm_event_do_handlers source/blender/windowmanager/intern/wm_event_system.c:3378:17 - 16 WM_main source/blender/windowmanager/intern/wm.c:647:5 - 17 main source/creator/creator.c:519:5 #18 start (/usr/lib/system/libdyld.dylib:x86_64+0x163d4) ```

Added subscriber: @chemicalcrux

Changed status from 'Needs Triage' to: 'Confirmed'

Added subscriber: @ankitm

Here's the issue:

static int bm_face_len_cmp(const void *v1, const void *v2)
{
  const BMFace *f1 = v1, *f2 = v2;

qsort is passing a BMFace** to the cmp function, which then tries to interpret it as a BMFace*. This runs off the end of the pointer and sets off ASan.

Casting to BMFace** and then dereferencing makes things work. Interestingly, the operator was still working properly even with a bogus sort function -- maybe it was just running slower, or something?

Should be an easy fix. I will take a stab at making a patch for this.

Here's the issue: ``` static int bm_face_len_cmp(const void *v1, const void *v2) { const BMFace *f1 = v1, *f2 = v2; ``` `qsort` is passing a `BMFace**` to the cmp function, which then tries to interpret it as a `BMFace*`. This runs off the end of the pointer and sets off ASan. Casting to `BMFace**` and then dereferencing makes things work. Interestingly, the operator was still working properly even with a bogus sort function -- maybe it was just running slower, or something? Should be an easy fix. I will take a stab at making a patch for this.

This issue was referenced by 129798cacb

This issue was referenced by 129798cacbd9e1cd7f94a8f0c3f8b669d89ca0dc

This issue was referenced by 8dd18a77e7

This issue was referenced by 8dd18a77e72444c5a9cc60c1043fa96b28260d9a

This issue was referenced by e178a273fa

This issue was referenced by e178a273fa7f5c67a617d682b1387cb42a6987cb

Changed status from 'Confirmed' to: 'Resolved'

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Select Similar Face Regions triggers AddressSanitizer crash #89247