On Thu 20-12-18 15:31:56, 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(). > > * Take into account DEFERRED_STRUCT_PAGE_INIT. > */ > if (early_pfn_to_nid(pfn) != nid) > continue; > > However, it did not handle it well in init_pages_in_zone() which end up > calling page_to_nid(). > > [ 11.917212] page:ffffea0004200000 is uninitialized and poisoned > [ 11.917220] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff > ffffffffffffffff > [ 11.921745] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff > ffffffffffffffff > [ 11.924523] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > [ 11.926498] page_owner info is not active (free page?) > [ 12.329560] kernel BUG at include/linux/mm.h:990! > [ 12.337632] RIP: 0010:init_page_owner+0x486/0x520 > > Since there is no other routines depend on page_ext_init() in > start_kernel(), just move it after page_alloc_init_late() to ensure that > there is no deferred pages need to de dealt with. If deselected > DEFERRED_STRUCT_PAGE_INIT, it is still better to call page_ext_init() > earlier, so page owner could catch more early page allocation call > sites. This gives us a good compromise between catching good and bad > call sites (See the v1 patch [1]) in case of DEFERRED_STRUCT_PAGE_INIT. > > [1] https://lore.kernel.org/lkml/20181220060303.38686-1-cai@xxxxxx/ > > Fixes: fe53ca54270 (mm: use early_pfn_to_nid in page_ext_init) > Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx> > Signed-off-by: Qian Cai <cai@xxxxxx> > --- > > v3: still call page_ext_init() earlier if DEFERRED_STRUCT_PAGE_INIT=n. > > v2: postpone page_ext_init() to after page_alloc_init_late(). > > init/main.c | 5 +++++ > mm/page_ext.c | 3 +-- > 2 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/init/main.c b/init/main.c > index 2b7b7fe173c9..5d9904370f76 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -696,7 +696,9 @@ asmlinkage __visible void __init start_kernel(void) > initrd_start = 0; > } > #endif > +#ifndef CONFIG_DEFERRED_STRUCT_PAGE_INIT > page_ext_init(); > +#endif > kmemleak_init(); > setup_per_cpu_pageset(); > numa_policy_init(); > @@ -1147,6 +1149,9 @@ static noinline void __init kernel_init_freeable(void) > sched_init_smp(); > > page_alloc_init_late(); > +#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT > + page_ext_init(); > +#endif > > do_basic_setup(); Is this really necessary? Why cannot we simply postpone page_ext_init unconditioanally? > > diff --git a/mm/page_ext.c b/mm/page_ext.c > index ae44f7adbe07..d76fd51e312a 100644 > --- a/mm/page_ext.c > +++ b/mm/page_ext.c > @@ -399,9 +399,8 @@ void __init page_ext_init(void) > * -------------pfn--------------> > * N0 | N1 | N2 | N0 | N1 | N2|.... > * > - * Take into account DEFERRED_STRUCT_PAGE_INIT. > */ > - if (early_pfn_to_nid(pfn) != nid) > + if (pfn_to_nid(pfn) != nid) > continue; > if (init_section_page_ext(pfn, nid)) > goto oom; Also this doesn't seem to be related, right? -- Michal Hocko SUSE Labs
