Crash due to Assert on Line Angle action (QT6) about librecad HOT 2 CLOSED

Amazing, this is a serious bug from the very beginning.

It was clearly a potential buffer overflow as the assertion as identified, so previous, the bug was there, but as there was no assertion, so not identified.

The bug is also quite clear:

1. The string length is assigned to a variable "ls";
2. The string is allowed to be trimmed from back, but "ls" is not updated, so potentially larger than the string length;
3. The string is now trimmed from front, now, with an assumed length "ls", which is larger, so the comparison goes beyond the buffer size, and potentially causing writing beyond the string size.

It has been running properly so far, because the QString buffer is probably not immediately reduced after trimming in step 2, but it's still considered an undefined behavior.

from librecad.

The issue is so serious, I also pushed the fix to the 2.2.1 release candidate branch

from librecad.