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() and no real benefit to call it so early, just move it
after page_alloc_init_late() to ensure that there is no deferred pages
need to de dealt with.
Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Qian Cai <cai@xxxxxx>
---
v2: postpone init_page_ext() to after page_alloc_init_late().
init/main.c | 2 +-
mm/page_ext.c | 3 +--
2 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/init/main.c b/init/main.c
index 2b7b7fe173c9..1aeb062b2cb7 100644
--- a/init/main.c
+++ b/init/main.c
@@ -696,7 +696,6 @@ asmlinkage __visible void __init start_kernel(void)
initrd_start = 0;
}
#endif
- page_ext_init();
kmemleak_init();
setup_per_cpu_pageset();
numa_policy_init();
@@ -1147,6 +1146,7 @@ static noinline void __init kernel_init_freeable(void)
sched_init_smp();
page_alloc_init_late();
+ page_ext_init();
do_basic_setup();
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;
--
2.17.2 (Apple Git-113)
