CVE-2021-47018

Summary

CVE-2021-47018 is a vulnerability affecting the Linux kernel on PPC64 architecture. The issue lies in the incorrect definition of the fixmap area, which is used to manage fixed-sized memory regions. Currently, this area is defined either at the top of the address space or just below the KASAN region. However, this definition is not valid for PPC64 systems. Therefore, a fix has been implemented to define the fixmap area at the top of the I/O space instead. Due to circular dependencies, it was not possible to include asm/fixmap.h in asm/book3s/64/pgtable.h directly. To address this, a fixed size AREA has been defined at the top of the I/O space for the fixmap region, ensuring it is large enough during the build process.

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