On 11.10.19 16:06, David Hildenbrand wrote:
From: Qian Cai <cai@xxxxxx>
Uninitialized memmaps contain garbage and in the worst case trigger
kernel BUGs, especially with CONFIG_PAGE_POISONING. They should not get
touched.
For example, when not onlining a memory block that is spanned by a zone
and reading /proc/pagetypeinfo with CONFIG_DEBUG_VM_PGFLAGS and
CONFIG_PAGE_POISONING, we can trigger a kernel BUG:
:/# echo 1 > /sys/devices/system/memory/memory40/online
:/# echo 1 > /sys/devices/system/memory/memory42/online
:/# cat /proc/pagetypeinfo > test.file
[ 42.489856] page:fffff2c585200000 is uninitialized and poisoned
[ 42.489861] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
[ 42.492235] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
[ 42.493501] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
[ 42.494533] There is not page extension available.
[ 42.495358] ------------[ cut here ]------------
[ 42.496163] kernel BUG at include/linux/mm.h:1107!
[ 42.497069] invalid opcode: 0000 [#1] SMP NOPTI
Please not that this change does not affect ZONE_DEVICE, because
pagetypeinfo_showmixedcount_print() is called from
mm/vmstat.c:pagetypeinfo_showmixedcount() only for populated zones, and
ZONE_DEVICE is never populated (zone->present_pages always 0).
Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") # visible after d0dc12e86b319
Signed-off-by: Qian Cai <cai@xxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Miles Chen <miles.chen@xxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Qian Cai <cai@xxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[ move check to outer loop, add comment, rephrase description ]
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
Cai asked me to follow up on:
[PATCH] mm/page_owner: fix a crash after memory offline
---
mm/page_owner.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index dee931184788..7d149211f6be 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -284,7 +284,8 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m,
* not matter as the mixed block count will still be correct
*/
for (; pfn < end_pfn; ) {
- if (!pfn_valid(pfn)) {
+ page = pfn_to_online_page(pfn);
+ if (!page) {
pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
continue;
}
@@ -292,13 +293,13 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m,
block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
block_end_pfn = min(block_end_pfn, end_pfn);
- page = pfn_to_page(pfn);
pageblock_mt = get_pageblock_migratetype(page);
for (; pfn < block_end_pfn; pfn++) {
if (!pfn_valid_within(pfn))
continue;
+ /* The pageblock is online, no need to recheck. */
page = pfn_to_page(pfn);
if (page_zone(page) != zone)
I guess it's best to just
Cc: stable@xxxxxxxxxxxxxxx # v4.13+
here as well. Can be cheery-picked.
@Andrew, can you add that?
--
Thanks,
David / dhildenb
