https://bugs.kde.org/show_bug.cgi?id=484622
Bug ID: 484622
Summary: Forcing GDS mitigation for older CPUs on Linux makes
krita crash
Classification: Applications
Product: krita
Version: 5.2.2
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: crash
Priority: NOR
Component: General
Assignee: krita-bugs-n...@kde.org
Reporter: bugrepor...@freenet.de
Target Milestone: ---
Created attachment 167863
--> https://bugs.kde.org/attachment.cgi?id=167863&action=edit
Krita backtrace and disassembly
When the Gather Data Sampling mitigation is forced on Linux for older CPUs
(i.e. Intel Core 6th Gen Skylake) that are affected by the GDS vulnerability,
AVX/AVX2 instructions are disabled, because there is no microcode update
available.
On affected systems 'lscpu' reports:
…
Vulnerabilities:
Gather data sampling: Mitigation; AVX disabled, no microcode
…
This causes Krita to crash, because something is wrong with the CPU feature
detection (xsimd function call) in Krita and it's still trying to use VEX
instructions. Similar problems were already reported and fixed for pcre2 (regex
library) and Babl/Gimp. See the attached gdb backtrace/disassembly and the
following pcre2 issue (reported by me) for further information.
https://github.com/PCRE2Project/pcre2/issues/399
Babl/Gimp issue:
https://gitlab.gnome.org/GNOME/babl/-/issues/96#note_2056377
STEPS TO REPRODUCE
1. Force GDS mitigation by adding 'gather_data_sampling=force' as kernel
parameter on an affected system (AVX/AVX2 disabled).
2. Start krita and try to open a PNG image.
OBSERVED RESULT
Krita crashes with 'SIGILL, Illegal instruction'.
EXPECTED RESULT
Krita should not crash and open the file.
SOFTWARE/OS VERSIONS
Arch Linux - Linux kernel 6.8.1
krita 5.2.2-8 from the repo (compiled with -march=x86-64)
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