CVE-2024-26947: In the Linux kernel, the following vulnerability has been resolved: ARM: 9359/1: flush: check if the folio is reserved

A bug in the Linux kernel's ARM architecture code caused system crashes when the kernel tried to flush cache memory (clear temporary copies of data stored near the CPU) for reserved memory addresses that weren't mapped by the kernel. The problem occurred because an earlier change made pfn_valid() (a function that checks if a physical memory address is valid) too permissive, allowing it to accept reserved memory without proper verification.