Subject: + mm-page_alloc-make-first_page-visible-before-pagetail.patch added to -mm tree
To: rientjes@xxxxxxxxxx,Holger.Kiehl@xxxxxx,aquini@xxxxxxxxxx,cl@xxxxxxxxx,mgorman@xxxxxxx,mhocko@xxxxxxx,stable@xxxxxxxxxxxxxxx,vbabka@xxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 04 Feb 2014 16:33:05 -0800
The patch titled
Subject: mm, page_alloc: make first_page visible before PageTail
has been added to the -mm tree. Its filename is
mm-page_alloc-make-first_page-visible-before-pagetail.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-make-first_page-visible-before-pagetail.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-make-first_page-visible-before-pagetail.patch
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From: David Rientjes <rientjes@xxxxxxxxxx>
Subject: mm, page_alloc: make first_page visible before PageTail
Commit bf6bddf1924e ("mm: introduce compaction and migration for ballooned
pages") introduces page_count(page) into memory compaction which
dereferences page->first_page if PageTail(page).
This caused Holger to observe a very rare NULL pointer dereference on the
aforementioned page_count(page).
Introduce a store memory barrier to ensure page->first_page is properly
initialized so that code that does page_count(page) on pages off the lru
always have a valid p->first_page.
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Reported-by: Holger Kiehl <Holger.Kiehl@xxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Rafael Aquini <aquini@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff -puN mm/page_alloc.c~mm-page_alloc-make-first_page-visible-before-pagetail mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_alloc-make-first_page-visible-before-pagetail
+++ a/mm/page_alloc.c
@@ -369,9 +369,11 @@ void prep_compound_page(struct page *pag
__SetPageHead(page);
for (i = 1; i < nr_pages; i++) {
struct page *p = page + i;
- __SetPageTail(p);
set_page_count(p, 0);
p->first_page = page;
+ /* Make sure p->first_page is always valid for PageTail() */
+ smp_wmb();
+ __SetPageTail(p);
}
}
_
Patches currently in -mm which might be from rientjes@xxxxxxxxxx are
documentation-kernel-parameterstxt-fix-memmap=-language.patch
mm-__set_page_dirty_nobuffers-uses-spin_lock_irqseve-instead-of-spin_lock_irq.patch
mm-slub-list_lock-may-not-be-held-in-some-circumstances.patch
fs-filec-fdtable-avoid-triggering-ooms-from-alloc_fdmem.patch
mm-page_alloc-make-first_page-visible-before-pagetail.patch
numa-mem-hotplug-initialize-numa_kernel_nodes-in-numa_clear_kernel_node_hotplug.patch
numa-mem-hotplug-fix-array-index-overflow-when-synchronizing-nid-to-memblockreserved.patch
kthread-ensure-locality-of-task_struct-allocations.patch
mm-compaction-ignore-pageblock-skip-when-manually-invoking-compaction.patch
mm-vmscan-shrink_slab-rename-max_pass-freeable.patch
mm-utilc-add-kstrimdup.patch
cpusets-allocate-heap-only-when-required.patch
linux-next.patch
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