On Thu 20-12-18 01:03:03, Qian Cai wrote: > When booting a system with "page_owner=on", > > start_kernel > page_ext_init > invoke_init_callbacks > init_section_page_ext > init_page_owner > init_early_allocated_pages > init_zones_in_node > init_pages_in_zone > lookup_page_ext > page_to_nid > > The issue here is that page_to_nid() will not work since some page > flags have no node information until later in page_alloc_init_late() due > to DEFERRED_STRUCT_PAGE_INIT. Hence, it could trigger an out-of-bounds > access with an invalid nid. > > [ 8.666047] UBSAN: Undefined behaviour in ./include/linux/mm.h:1104:50 > [ 8.672603] index 7 is out of range for type 'zone [5]' > > Also, kernel will panic since flags were poisoned earlier with, > > CONFIG_DEBUG_VM_PGFLAGS=y > CONFIG_NODE_NOT_IN_PAGE_FLAGS=n > > start_kernel > setup_arch > pagetable_init > paging_init > sparse_init > sparse_init_nid > memblock_alloc_try_nid_raw > > Although later it tries to set page flags for pages in reserved bootmem > regions, > > mm_init > mem_init > memblock_free_all > free_low_memory_core_early > reserve_bootmem_region > > there could still have some freed pages from the page allocator but yet > to be initialized due to DEFERRED_STRUCT_PAGE_INIT. It have already been > dealt with a bit in page_ext_init(). Is there any reason why we cannot postpone page_ext initialization to after all the memory is initialized? -- Michal Hocko SUSE Labs
