From the implementation of the text console supplied with the Linux kernel , which provides the ability to scroll the text back (CONFIG_VGACON_SOFT_SCROLLBACK). The code was removed due to the presence of errors, which turned out to be no one to fix due to the lack of a maintainer who oversees the development of vgacon.
In the summer, vgacon was identified and A vulnerability (CVE-2020-14331) that could lead to a buffer overflow due to the lack of proper checks for available memory in the scroll buffer. The vulnerability attracted the attention of developers, who organized fuzz testing of the vgacon code in .
Additional checks revealed several more similar problems in the vgacon code, as well as problems in the software implementation of scrolling in the fbcon driver. Unfortunately, the problematic code has been left unmaintained for a long time, presumably due to the fact that developers have switched to using graphical consoles and text consoles have fallen out of use (people continue to use the vgacon and fbcon consoles, but they have not been the main kernel interface for decades and such extended features like scrolling built into the driver (Shift+PageUp/PageDown) are presumably of little use).
In this regard, Linus Torvalds decided not to try to maintain unclaimed code, but simply to remove it. If there are users who need this functionality, the code to support scrolling in the console will be returned to the core as soon as there is a maintainer ready to take care of its maintenance.
Source: opennet.ru