There is a bug In file
    linux/arch/um/kernel/physmem.c  init_mem() functions:

*int* *init_maps*(*unsigned* *long* physmem, *unsigned* *long* iomem,
*unsigned* *long* highmem)
{
	*struct* page *p, *map;
	*unsigned* *long* phys_len, phys_pages, highmem_len, highmem_pages;
	*unsigned* *long* iomem_len, iomem_pages, total_len, total_pages;
	*int* i;

	phys_pages = physmem >> PAGE_SHIFT;
	phys_len = phys_pages * *sizeof*(*struct* page);

	iomem_pages = iomem >> PAGE_SHIFT;
	iomem_len = iomem_pages * *sizeof*(*struct* page);

	highmem_pages = highmem >> PAGE_SHIFT;
	highmem_len = highmem_pages * *sizeof*(*struct* page);

	total_pages = phys_pages + iomem_pages + highmem_pages;
	total_len = phys_len + iomem_pages + highmem_len;

	*if*(kmalloc_ok){
		map = kmalloc(total_len, GFP_KERNEL);
		*if*(map == NULL)
			map = vmalloc(total_len);
	}
	*else* map = alloc_bootmem_low_pages(total_len);

	*if*(map == NULL)
		*return*(-ENOMEM);

	*for*(i = 0; i < total_pages; i++){
		p = &map[i];
		set_page_count(p, 0);
		SetPageReserved(p);
		INIT_LIST_HEAD(&p->list);
	}

	mem_map = map;
	max_mapnr = total_pages;
	*return*(0);
}

this line should be

total_len = phys_len + iomem_len + highmem_len;


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