The patch titled
Subject: mm, compaction: fix wrong pfn handling in __reset_isolation_pfn()
has been added to the -mm tree. Its filename is
mm-compaction-fix-wrong-pfn-handling-in-__reset_isolation_pfn.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-fix-wrong-pfn-handling-in-__reset_isolation_pfn.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-fix-wrong-pfn-handling-in-__reset_isolation_pfn.patch
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------------------------------------------------------
From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm, compaction: fix wrong pfn handling in __reset_isolation_pfn()
Florian and Dave reported [1] a NULL pointer dereference in
__reset_isolation_pfn(). While the exact cause is unclear, staring at the
code revealed two bugs, which might be related.
One bug is that if zone starts in the middle of pageblock, block_page
might correspond to different pfn than block_pfn, and then the
pfn_valid_within() checks will check different pfn's than those accessed
via struct page. This might result in acessing an unitialized page in
CONFIG_HOLES_IN_ZONE configs.
The other bug is that end_page refers to the first page of next pageblock
and not last page of current pageblock. The online and valid check is
then wrong and with sections, the while (page < end_page) loop might
wander off actual struct page arrays.
[1] https://lore.kernel.org/linux-xfs/87o8z1fvqu.fsf@xxxxxxxxxxxxxxxxx/
Link: http://lkml.kernel.org/r/20191008152915.24704-1-vbabka@xxxxxxx
Fixes: 6b0868c820ff ("mm/compaction.c: correct zone boundary handling when resetting pageblock skip hints")
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Reported-by: Florian Weimer <fw@xxxxxxxxxxxxx>
Reported-by: Dave Chinner <david@xxxxxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/mm/compaction.c~mm-compaction-fix-wrong-pfn-handling-in-__reset_isolation_pfn
+++ a/mm/compaction.c
@@ -270,14 +270,15 @@ __reset_isolation_pfn(struct zone *zone,
/* Ensure the start of the pageblock or zone is online and valid */
block_pfn = pageblock_start_pfn(pfn);
- block_page = pfn_to_online_page(max(block_pfn, zone->zone_start_pfn));
+ block_pfn = max(block_pfn, zone->zone_start_pfn);
+ block_page = pfn_to_online_page(block_pfn);
if (block_page) {
page = block_page;
pfn = block_pfn;
}
/* Ensure the end of the pageblock or zone is online and valid */
- block_pfn += pageblock_nr_pages;
+ block_pfn = pageblock_end_pfn(pfn) - 1;
block_pfn = min(block_pfn, zone_end_pfn(zone) - 1);
end_page = pfn_to_online_page(block_pfn);
if (!end_page)
@@ -303,7 +304,7 @@ __reset_isolation_pfn(struct zone *zone,
page += (1 << PAGE_ALLOC_COSTLY_ORDER);
pfn += (1 << PAGE_ALLOC_COSTLY_ORDER);
- } while (page < end_page);
+ } while (page <= end_page);
return false;
}
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-page_owner-fix-off-by-one-error-in-__set_page_owner_handle.patch
mm-page_owner-decouple-freeing-stack-trace-from-debug_pagealloc.patch
mm-page_owner-decouple-freeing-stack-trace-from-debug_pagealloc-v3.patch
mm-page_owner-rename-flag-indicating-that-page-is-allocated.patch
mm-compaction-fix-wrong-pfn-handling-in-__reset_isolation_pfn.patch
