Modal knife tool can crash if used on hidden object #116262

New Issue

fist-in-face · 2023-12-17T05:52:09+01:00

fist-in-face commented

2023-12-17 05:52:09 +01:00

System Information
Operating system: Windows 11
Graphics card: Gt 1030

Blender Version
Broken: version: 3.6.7, branch: blender-v3.6-release, commit date: 2023-12-11 16:28, hash: cbd81f283d58
Broken: 3.5
Worked: (newest version of Blender that worked as expected)

Short description of error
if I cut an object that I cant see with the knife tool it just auto closes blender

Exact steps for others to reproduce the error

select cube in new scene
go to edit mode
select the knife tool
cut the cube making a shape in it like a triangle or square
then press space to save the cut
then press the eye icon on the cube
try to cut the invisible cube
note this glitch only happens sometimes.
Based on the default startup or an attached .blend file (as simple as possible).

ExceptionCode         : EXCEPTION_ACCESS_VIOLATION
Exception Address     : 0x00007FF785B87A00
Exception Module      : blender.exe
Exception Flags       : 0x00000000
Exception Parameters  : 0x2
	Parameters[0] : 0x0000000000000000
	Parameters[1] : 0x0000000000000030


Stack trace:
blender.exe         :0x00007FF785B87A00  mul_v3_m4v3
blender.exe         :0x00007FF78229D660  get_bm_knife_vert
blender.exe         :0x00007FF7822A0DF0  knife_get_face_kedges
blender.exe         :0x00007FF78229EDD0  knife_find_closest_edge_of_face
blender.exe         :0x00007FF7822A2610  knife_snap_update_from_mval
blender.exe         :0x00007FF7822A2E60  knife_update_active
blender.exe         :0x00007FF7822A6AD0  knifetool_update_mval_i
blender.exe         :0x00007FF7822A5610  knifetool_modal

**System Information** Operating system: Windows 11 Graphics card: Gt 1030 **Blender Version** Broken: version: 3.6.7, branch: blender-v3.6-release, commit date: 2023-12-11 16:28, hash: `cbd81f283d58` Broken: 3.5 Worked: (newest version of Blender that worked as expected) **Short description of error** if I cut an object that I cant see with the knife tool it just auto closes blender **Exact steps for others to reproduce the error** 1. select cube in new scene 2. go to edit mode 3. select the knife tool 4. cut the cube making a shape in it like a triangle or square 5. then press space to save the cut 6. then press the eye icon on the cube 7. try to cut the invisible cube note this glitch only happens sometimes. Based on the default startup or an attached .blend file (as simple as possible). ``` ExceptionCode : EXCEPTION_ACCESS_VIOLATION Exception Address : 0x00007FF785B87A00 Exception Module : blender.exe Exception Flags : 0x00000000 Exception Parameters : 0x2 Parameters[0] : 0x0000000000000000 Parameters[1] : 0x0000000000000030 Stack trace: blender.exe :0x00007FF785B87A00 mul_v3_m4v3 blender.exe :0x00007FF78229D660 get_bm_knife_vert blender.exe :0x00007FF7822A0DF0 knife_get_face_kedges blender.exe :0x00007FF78229EDD0 knife_find_closest_edge_of_face blender.exe :0x00007FF7822A2610 knife_snap_update_from_mval blender.exe :0x00007FF7822A2E60 knife_update_active blender.exe :0x00007FF7822A6AD0 knifetool_update_mval_i blender.exe :0x00007FF7822A5610 knifetool_modal ```

2023-12-16 23-50-12.mkv

4.8 MiB

fist-in-face added the

labels 2023-12-17 05:52:10 +01:00

Jesse Yurkovich commented

2023-12-17 07:04:20 +01:00

Confirmed in 3.6 as well as 4.x

Jesse Yurkovich added

and removed

labels 2023-12-17 07:04:32 +01:00

Jesse Yurkovich changed title from ~~knife tool~~ to Modal knife tool can crash if used on hidden object

2023-12-17 07:08:38 +01:00

Philipp Oeser commented

2023-12-18 13:50:36 +01:00

Looked into this a bit, think I can fix

Philipp Oeser self-assigned this 2023-12-18 13:50:44 +01:00

Pratik Borhade commented

2023-12-26 06:49:36 +01:00

Looks like kcd->objects_len is 0 because hidden objects (BKE_base_is_visible) are not iterated in FOREACH_BASE_IN_MODE_BEGIN. So the kcd->objects_info points to garbage memory.
Not sure what should be the fix here. Mismatch between objects_len and objects_info array len can easily happen.
BTW crash does not happen in 3.3

Looks like `kcd->objects_len` is 0 because hidden objects (`BKE_base_is_visible`) are not iterated in `FOREACH_BASE_IN_MODE_BEGIN`. So the `kcd->objects_info` points to garbage memory. Not sure what should be the fix here. Mismatch between `objects_len` and `objects_info` array len can easily happen. BTW crash does not happen in 3.3

Philipp Oeser commented

2023-12-27 13:06:19 +01:00

I can get 3.3 to crash as well.

The most apparent problem is the case when objects_len is zero, but actually this mismatch can have other bad consequences because of the garbage memory. Stuff behaves unexpected if you for example have multiple objects in editmode and hide some of them.

Following the principle of "never act on hidden stuff", I think it is actually wrong to include a backbuffer fallback in knife_find_closest_face when raycasting fails, this makes all following code confusing/wrong since we are working with coordinates / faces under the assumption there would be a valid/corresponding object to it in KnifeTool_OpData > objects -- which is not the case...

Still thinking of where the best place would be to prevent all this...

I can get 3.3 to crash as well. The most apparent problem is the case when `objects_len` is zero, but actually this mismatch can have other bad consequences because of the garbage memory. Stuff behaves unexpected if you for example have multiple objects in editmode and hide some of them. Following the principle of "never act on hidden stuff", I think it is actually wrong to include a backbuffer fallback in `knife_find_closest_face` when raycasting fails, this makes all following code confusing/wrong since we are working with coordinates / faces under the assumption there would be a valid/corresponding object to it in `KnifeTool_OpData` > `objects` -- which is not the case... Still thinking of where the best place would be to prevent all this...

👍 1

Philipp Oeser referenced a pull request that will close this issue

2024-03-12 15:28:02 +01:00

Fix #116262: Modal knife tool can crash if used on hidden object #119383

Philipp Oeser commented

2024-03-12 16:03:53 +01:00

Since this is a crasher, will also raise priority here

Philipp Oeser added

Priority

High

and removed

Priority