The patch titled
Subject: mm/page_owner: don't access uninitialized memmaps when reading /proc/pagetypeinfo
has been added to the -mm tree. Its filename is
mm-page_owner-dont-access-uninitialized-memmaps-when-reading-proc-pagetypeinfo.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_owner-dont-access-uninitialized-memmaps-when-reading-proc-pagetypeinfo.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_owner-dont-access-uninitialized-memmaps-when-reading-proc-pagetypeinfo.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Qian Cai <cai@xxxxxx>
Subject: mm/page_owner: don't access uninitialized memmaps when reading /proc/pagetypeinfo
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 note 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).
[david@xxxxxxxxxx: move check to outer loop, add comment, rephrase description]
Link: http://lkml.kernel.org/r/20191011140638.8160-1-david@xxxxxxxxxx
Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") # visible after d0dc12e86b319
Signed-off-by: Qian Cai <cai@xxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
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>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_owner.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/mm/page_owner.c~mm-page_owner-dont-access-uninitialized-memmaps-when-reading-proc-pagetypeinfo
+++ a/mm/page_owner.c
@@ -271,7 +271,8 @@ void pagetypeinfo_showmixedcount_print(s
* 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;
}
@@ -279,13 +280,13 @@ void pagetypeinfo_showmixedcount_print(s
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)
_
Patches currently in -mm which might be from cai@xxxxxx are
mm-slub-fix-a-deadlock-in-show_slab_objects.patch
mm-page_owner-dont-access-uninitialized-memmaps-when-reading-proc-pagetypeinfo.patch
z3fold-add-inter-page-compaction-fix.patch
hugetlb-remove-unused-hstate-in-hugetlb_fault_mutex_hash-fix-fix.patch
