| The vulnerability, identified as CVE-2021-47018, affects the Linux kernel's powerpc/64 architecture. Specifically, it concerns the definition of the fixmap area, which is currently defined at the top of the address space or just below KASAN (Kernel Address Space Layout Randomization). However, this definition is not valid for PPC64 architectures. |
| |
| To fix this issue, the fixmap area needs to be redefined at the top of the I/O space for PPC64. Due to circular dependencies, it's not possible to include `asm/fixmap.h` in `asm/book3s/64/pgtable.h`, so a fixed-size AREA is defined at the top of the I/O space for fixmap, and ensured during build that the size is big enough. |
| |
| The vulnerability was introduced in Linux kernel version 5.5 with commit 265c3491c4bc and has been fixed in various subsequent versions, including 5.10.37, 5.11.21, 5.12.4, and 5.13. The affected files include `arch/powerpc/include/asm/book3s/64/pgtable.h`, `arch/powerpc/include/asm/fixmap.h`, and `arch/powerpc/include/asm/nohash/64/pgtable.h`. |
| |
