The patch titled
Avoid unsafe use of struct pages in move_freepages when CONFIG_HOLES_IN_ZONE is set
has been added to the -mm tree. Its filename is
move-free-pages-between-lists-on-steal-avoid-unsafe-use-of-struct-pages-in-move_freepages-when-config_holes_in_zone-is-set.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Avoid unsafe use of struct pages in move_freepages when CONFIG_HOLES_IN_ZONE is set
From: Mel Gorman <mel@xxxxxxxxx>
In the majority of situations, mem_map is guaranteed to be valid within a
MAX_ORDER_NR_PAGES block of pages. However, when CONFIG_HOLES_IN_ZONE is
set, there is no guarantee that mem_map exists for the entire block. This
means that when checking struct pages around a known valid page, there is
no guarantee they are valid.
move_freepages() operates on a MAX_ORDER_NR_PAGES range of pages based on
a known valid page retrieved from the free lists. However, a bug check is
unsafe when CONFIG_HOLES_IN_ZONE is set and pfn_valid() is called too late.
This patch disables the bug check when CONFIG_HOLES_IN_ZONE and checks
pfn_valid() earlier before calling PageBuddy(). It applies on top of
move-free-pages-between-lists-on-steal-fix-2.patch from Yasunori Goto in
-mm.
Credit to Bjorn Helgaas for reporting this bug and testing.
Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
Cc: Bjorn Helgaas <bjorn.helgaas@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff -puN mm/page_alloc.c~move-free-pages-between-lists-on-steal-avoid-unsafe-use-of-struct-pages-in-move_freepages-when-config_holes_in_zone-is-set mm/page_alloc.c
--- a/mm/page_alloc.c~move-free-pages-between-lists-on-steal-avoid-unsafe-use-of-struct-pages-in-move_freepages-when-config_holes_in_zone-is-set
+++ a/mm/page_alloc.c
@@ -673,13 +673,18 @@ int move_freepages(struct zone *zone,
unsigned long order;
int blocks_moved = 0;
+#ifndef CONFIG_HOLES_IN_ZONE
+ /*
+ * page_zone is not safe to call in this context when
+ * CONFIG_HOLES_IN_ZONE is set. This bug check is probably redundant
+ * anyway as we check zone boundaries in move_freepages_block().
+ * Remove at a later date when no bug reports exist related to
+ * CONFIG_PAGE_GROUP_BY_MOBILITY
+ */
BUG_ON(page_zone(start_page) != page_zone(end_page - 1));
+#endif
for (page = start_page; page < end_page;) {
- if (!PageBuddy(page)) {
- page++;
- continue;
- }
#ifdef CONFIG_HOLES_IN_ZONE
if (!pfn_valid(page_to_pfn(page))) {
page++;
@@ -687,6 +692,11 @@ int move_freepages(struct zone *zone,
}
#endif
+ if (!PageBuddy(page)) {
+ page++;
+ continue;
+ }
+
order = page_order(page);
list_del(&page->lru);
list_add(&page->lru,
_
Patches currently in -mm which might be from mel@xxxxxxxxx are
add-a-bitmap-that-is-used-to-track-flags-affecting-a-block-of-pages.patch
add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated.patch
add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated-fix.patch
add-__gfp_movable-for-callers-to-flag-allocations-from-low-memory-that-may-be-migrated.patch
split-the-free-lists-for-movable-and-unmovable-allocations.patch
choose-pages-from-the-per-cpu-list-based-on-migration-type.patch
add-a-configure-option-to-group-pages-by-mobility.patch
drain-per-cpu-lists-when-high-order-allocations-fail.patch
move-free-pages-between-lists-on-steal.patch
move-free-pages-between-lists-on-steal-fix.patch
move-free-pages-between-lists-on-steal-fix-2.patch
move-free-pages-between-lists-on-steal-avoid-unsafe-use-of-struct-pages-in-move_freepages-when-config_holes_in_zone-is-set.patch
group-short-lived-and-reclaimable-kernel-allocations.patch
group-high-order-atomic-allocations.patch
bias-the-placement-of-kernel-pages-at-lower-pfns.patch
be-more-agressive-about-stealing-when-migrate_reclaimable-allocations-fallback.patch
fix-corruption-of-memmap-on-ia64-sparsemem-when-mem_section-is-not-a-power-of-2.patch
create-the-zone_movable-zone.patch
allow-huge-page-allocations-to-use-gfp_high_movable.patch
x86-specify-amount-of-kernel-memory-at-boot-time.patch
ppc-and-powerpc-specify-amount-of-kernel-memory-at-boot-time.patch
x86_64-specify-amount-of-kernel-memory-at-boot-time.patch
ia64-specify-amount-of-kernel-memory-at-boot-time.patch
add-documentation-for-additional-boot-parameter-and-sysctl.patch
ext2-reservations.patch
add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated-swap-prefetch.patch
add-debugging-aid-for-memory-initialisation-problems.patch
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