CVE-2025-38681 mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd()

In the Linux kernel, the following vulnerability has been resolved: mm/ptdump: take the memory hotplug lock inside ptdumpwalkpgd Memory hot remove unmaps and tears down various kernel page table regions as required. The ptdump code can race with concurrent modifications of the kernel page tables...