Bug 429619

Summary:	Clicking "Add Preset" twice causes a crash in KisCanvasResourceProvider
Product:	[Applications] krita	Reporter:	David Conner <dconner.pro>
Component:	Brush engines	Assignee:	Halla Rempt <halla>
Status:	RESOLVED FIXED
Severity:	normal	CC:	dconner.pro, halla
Priority:	NOR
Version First Reported In:	git master (please specify the git hash!)
Target Milestone:	---
Platform:	Compiled Sources
OS:	Linux
Latest Commit:	https://invent.kde.org/graphics/krita/commit/747d5dbd59b40c6239745ef53dc74b6575a2e8a1	Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	New crash information added by DrKonqi

Description David Conner 2020-11-25 05:20:16 UTC

SUMMARY

I believe the cause is an uncaught null pointer.

kis_canvas_resource_provider.cpp:178 

```
Q_ASSERT(preset->valid());
```

STEPS TO REPRODUCE
1. Open/create a new document in Krita
2. Open the preset/brush editor
3. Click the (<) button, then click the (+) button to begin working on a new brush. I had the "Pixel Engine selected"
4. Draw something on the scratchpad to change the state of the new preset.
5. Toggle the widget's focus state (e.g. click "auto" then "pre-defined" then "auto")
6. Now an "invalid preset" indicator should be shown. If so, when you click the (+) to add a new brush preset, Krita will crash.

For some reason if I am debugging the app in CLion, then this crash will kill my KDE/Plasma session except for the mouse. I must then restart. Regardless, I triggered the bug multiple times. This does not happen if I am not debugging.

The CLion debugger did flag the line causing the problem.

I tried submitting a report in the crash response dialog. I believe this was Dr. Konqi, but I did not find a corresponding bug in bugs.kde.org.


OBSERVED RESULT

Krita crashes.

EXPECTED RESULT

An error message halting the Q_ASSERT check before it blows up or a teardown of the new (but invalid) brush preset.

SOFTWARE/OS VERSIONS
Windows: n/a
macOS: n/a
Linux/KDE Plasma: Garuda Linux (arch) with linux 5.9.10-zen1-1-zen
(available in About System)
KDE Plasma Version: 5.20.3
KDE Frameworks Version: 5.76.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION

Comment 1 David Conner 2020-11-25 06:21:49 UTC

if you go through all the same steps and click the "refresh" icon beside the "invalid" icon, that is another way to hit the same bug at L:178.

Also, when I am toggling through various brush presets, a similar error is being thrown for me at kis_canvas_resource_provider.cpp:198 (in the same valid() check for presets). This time, it is thrown in the `setPreviousPaintOpPreset()` member function.

I am not yet sure of the proper way to address this behavior.

Comment 2 David Conner 2020-11-25 06:26:27 UTC

Created attachment 133626 [details]
New crash information added by DrKonqi

krita (5.0.0-prealpha (git ec43d9e)) using Qt 5.15.2

- What I was doing when the application crashed:

I was clicking through the brush presets in the brush settings dialog

-- Backtrace (Reduced):
#7  0x00007f4c89452d59 in qt_assert_x(char const*, char const*, char const*, int) () at /usr/lib/libQt5Core.so.5
#8  0x00007f4c8d9763cd in KisCanvasResourceProvider::setPreviousPaintOpPreset(QSharedPointer<KisPaintOpPreset>) (this=<optimized out>, preset=...) at /data/dev/kritadev/krita/libs/ui/kis_canvas_resource_provider.cpp:198
#9  0x00007f4c8dca5033 in KisPaintopBox::setCurrentPaintop(QSharedPointer<KisPaintOpPreset>) (this=0x5633fe1ea200, preset=...) at /data/dev/kritadev/krita/libs/ui/kis_paintop_box.cc:623
#10 0x00007f4c8dcaa6d6 in KisPaintopBox::resourceSelected(QSharedPointer<KoResource>) (this=0x5633fe1ea200, resource=...) at /data/dev/kritadev/krita/libs/ui/kis_paintop_box.cc:594
#11 0x00007f4c8daa302e in KisPaintopBox::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (_o=<optimized out>, _c=<optimized out>, _id=<optimized out>, _a=<optimized out>) at /data/dev/kritadev/build/libs/ui/kritaui_autogen/EWIEGA46WW/moc_kis_paintop_box.cpp:242

Comment 3 Halla Rempt 2020-11-25 10:28:55 UTC

If you're using Linux to test, X11 will hang because the brush editor is a popup.  X11 blocks everything if there's a popup visibile, so if krita crashes while running in gdb and a popup is visible, X11 will hang. I start gdb from a text terminal to debug these things.

Comment 4 Halla Rempt 2020-11-25 10:34:24 UTC

Git commit 747d5dbd59b40c6239745ef53dc74b6575a2e8a1 by Boudewijn Rempt.
Committed on 25/11/2020 at 10:33.
Pushed by rempt into branch 'master'.

M  +2    -3    libs/ui/kis_canvas_resource_provider.cpp

https://invent.kde.org/graphics/krita/commit/747d5dbd59b40c6239745ef53dc74b6575a2e8a1