CVE-2024-35987

In the Linux kernel, the following vulnerability has been resolved: riscv:
Fix loading 64-bit NOMMU kernels past the start of RAM commit 3335068f8721
(“riscv: Use PUD/P4D/PGD pages for the linear mapping”) added logic to
allow using RAM below the kernel load address. However, this does not work
for NOMMU, where PAGE_OFFSET is fixed to the kernel load address. Since
that range of memory corresponds to PFNs below ARCH_PFN_OFFSET, mm
initialization runs off the beginning of mem_map and corrupts adjacent
kernel memory. Fix this by restoring the previous behavior for NOMMU
kernels.