This is a note to let you know that I've just added the patch titled
mm: migrate: fix an incorrect call of prep_transhuge_page()
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-migrate-fix-an-incorrect-call-of-prep_transhuge_page.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 40a899ed16486455f964e46d1af31fd4fded21c1 Mon Sep 17 00:00:00 2001
From: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
Date: Wed, 29 Nov 2017 16:11:12 -0800
Subject: mm: migrate: fix an incorrect call of prep_transhuge_page()
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From: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
commit 40a899ed16486455f964e46d1af31fd4fded21c1 upstream.
In https://lkml.org/lkml/2017/11/20/411, Andrea reported that during
memory hotplug/hot remove prep_transhuge_page() is called incorrectly on
non-THP pages for migration, when THP is on but THP migration is not
enabled. This leads to a bad state of target pages for migration.
By inspecting the code, if called on a non-THP, prep_transhuge_page()
will
1) change the value of the mapping of (page + 2), since it is used for
THP deferred list;
2) change the lru value of (page + 1), since it is used for THP's dtor.
Both can lead to data corruption of these two pages.
Andrea said:
"Pragmatically and from the point of view of the memory_hotplug subsys,
the effect is a kernel crash when pages are being migrated during a
memory hot remove offline and migration target pages are found in a
bad state"
This patch fixes it by only calling prep_transhuge_page() when we are
certain that the target page is THP.
Link: http://lkml.kernel.org/r/20171121021855.50525-1-zi.yan@xxxxxxxx
Fixes: 8135d8926c08 ("mm: memory_hotplug: memory hotremove supports thp migration")
Signed-off-by: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
Reported-by: Andrea Reale <ar@xxxxxxxxxxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 895ec0c4942e..a2246cf670ba 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -54,7 +54,7 @@ static inline struct page *new_page_nodemask(struct page *page,
new_page = __alloc_pages_nodemask(gfp_mask, order,
preferred_nid, nodemask);
- if (new_page && PageTransHuge(page))
+ if (new_page && PageTransHuge(new_page))
prep_transhuge_page(new_page);
return new_page;
Patches currently in stable-queue which might be from zi.yan@xxxxxxxxxxxxxx are
queue-4.14/mm-migrate-fix-an-incorrect-call-of-prep_transhuge_page.patch