The patch titled
Subject: mm: sanitize page->mapping for tail pages
has been added to the -mm tree. Its filename is
mm-sanitize-page-mapping-for-tail-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-sanitize-page-mapping-for-tail-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-sanitize-page-mapping-for-tail-pages.patch
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm: sanitize page->mapping for tail pages
We don't define meaning of page->mapping for tail pages. Currently it's
always NULL, which can be inconsistent with head page and potentially lead
to problems.
Let's poison the pointer to catch all illigal uses.
page_rmapping(), page_mapping() and page_anon_vma() are changed to look on
head page.
The only illegal use I've caught so far is __GPF_COMP pages from sound
subsystem, mapped with PTEs. do_shared_fault() is changed to use
page_rmapping() instead of direct access to fault_page->mapping.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Steve Capper <steve.capper@xxxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Jerome Marchand <jmarchan@xxxxxxxxxx
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/poison.h | 4 ++++
mm/huge_memory.c | 2 +-
mm/memory.c | 2 +-
mm/page_alloc.c | 6 ++++++
mm/util.c | 10 ++++++----
5 files changed, 18 insertions(+), 6 deletions(-)
diff -puN include/linux/poison.h~mm-sanitize-page-mapping-for-tail-pages include/linux/poison.h
--- a/include/linux/poison.h~mm-sanitize-page-mapping-for-tail-pages
+++ a/include/linux/poison.h
@@ -32,6 +32,10 @@
/********** mm/debug-pagealloc.c **********/
#define PAGE_POISON 0xaa
+/********** mm/page_alloc.c ************/
+
+#define TAIL_MAPPING ((void *) 0x01014A11 + POISON_POINTER_DELTA)
+
/********** mm/slab.c **********/
/*
* Magic nums for obj red zoning.
diff -puN mm/huge_memory.c~mm-sanitize-page-mapping-for-tail-pages mm/huge_memory.c
--- a/mm/huge_memory.c~mm-sanitize-page-mapping-for-tail-pages
+++ a/mm/huge_memory.c
@@ -1836,7 +1836,7 @@ static void __split_huge_page_refcount(s
*/
page_tail->_mapcount = page->_mapcount;
- BUG_ON(page_tail->mapping);
+ BUG_ON(page_tail->mapping != TAIL_MAPPING);
page_tail->mapping = page->mapping;
page_tail->index = page->index + i;
diff -puN mm/memory.c~mm-sanitize-page-mapping-for-tail-pages mm/memory.c
--- a/mm/memory.c~mm-sanitize-page-mapping-for-tail-pages
+++ a/mm/memory.c
@@ -3087,7 +3087,7 @@ static int do_shared_fault(struct mm_str
* pinned by vma->vm_file's reference. We rely on unlock_page()'s
* release semantics to prevent the compiler from undoing this copying.
*/
- mapping = fault_page->mapping;
+ mapping = page_rmapping(fault_page);
unlock_page(fault_page);
if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) {
/*
diff -puN mm/page_alloc.c~mm-sanitize-page-mapping-for-tail-pages mm/page_alloc.c
--- a/mm/page_alloc.c~mm-sanitize-page-mapping-for-tail-pages
+++ a/mm/page_alloc.c
@@ -473,6 +473,7 @@ void prep_compound_page(struct page *pag
for (i = 1; i < nr_pages; i++) {
struct page *p = page + i;
set_page_count(p, 0);
+ p->mapping = TAIL_MAPPING;
set_compound_head(p, page);
}
}
@@ -863,6 +864,10 @@ static int free_tail_pages_check(struct
ret = 0;
goto out;
}
+ if (page->mapping != TAIL_MAPPING) {
+ bad_page(page, "corrupted mapping in tail page", 0);
+ goto out;
+ }
if (unlikely(!PageTail(page))) {
bad_page(page, "PageTail not set", 0);
goto out;
@@ -873,6 +878,7 @@ static int free_tail_pages_check(struct
}
ret = 0;
out:
+ page->mapping = NULL;
clear_compound_head(page);
return ret;
}
diff -puN mm/util.c~mm-sanitize-page-mapping-for-tail-pages mm/util.c
--- a/mm/util.c~mm-sanitize-page-mapping-for-tail-pages
+++ a/mm/util.c
@@ -355,7 +355,9 @@ struct anon_vma *page_anon_vma(struct pa
struct address_space *page_mapping(struct page *page)
{
- unsigned long mapping;
+ struct address_space *mapping;
+
+ page = compound_head(page);
/* This happens if someone calls flush_dcache_page on slab page */
if (unlikely(PageSlab(page)))
@@ -368,10 +370,10 @@ struct address_space *page_mapping(struc
return swap_address_space(entry);
}
- mapping = (unsigned long)page->mapping;
- if (mapping & PAGE_MAPPING_FLAGS)
+ mapping = page->mapping;
+ if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
return NULL;
- return page->mapping;
+ return mapping;
}
int overcommit_ratio_handler(struct ctl_table *table, int write,
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
rcu-force-alignment-on-struct-callback_head-rcu_head.patch
mm-make-optimistic-check-for-swapin-readahead-fix.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix-2.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix-3.patch
mm-drop-page-slab_page.patch
slab-slub-use-page-rcu_head-instead-of-page-lru-plus-cast.patch
zsmalloc-use-page-private-instead-of-page-first_page.patch
mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page.patch
mm-make-compound_head-robust.patch
mm-use-unsigned-int-for-page-order.patch
mm-use-unsigned-int-for-compound_dtor-compound_order-on-64bit.patch
page-flags-trivial-cleanup-for-pagetrans-helpers.patch
page-flags-move-code-around.patch
page-flags-introduce-page-flags-policies-wrt-compound-pages.patch
page-flags-define-pg_locked-behavior-on-compound-pages.patch
page-flags-define-behavior-of-fs-io-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-lru-related-flags-on-compound-pages.patch
page-flags-define-behavior-slb-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-xen-related-flags-on-compound-pages.patch
page-flags-define-pg_reserved-behavior-on-compound-pages.patch
page-flags-define-pg_swapbacked-behavior-on-compound-pages.patch
page-flags-define-pg_swapcache-behavior-on-compound-pages.patch
page-flags-define-pg_mlocked-behavior-on-compound-pages.patch
page-flags-define-pg_uncached-behavior-on-compound-pages.patch
page-flags-define-pg_uptodate-behavior-on-compound-pages.patch
page-flags-look-at-head-page-if-the-flag-is-encoded-in-page-mapping.patch
mm-sanitize-page-mapping-for-tail-pages.patch
mm-support-madvisemadv_free-fix-3.patch
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