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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2016-01-15 16:52:07 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-15 17:56:32 -0800
commit1c290f642101e64f379e38ea0361d097c08e824d (patch)
tree14667c7c813fa14f6ce63e3fe7f5d14322fff0a6 /mm/page_alloc.c
parent822cdd1152265d87fcfc974e06c3b68f762987fd (diff)
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@linux.intel.com> Reviewed-by: Jérôme Glisse <jglisse@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Steve Capper <steve.capper@linaro.org> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Jerome Marchand <jmarchan@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ce63d603820f..d02d6436add0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -466,6 +466,7 @@ void prep_compound_page(struct page *page, unsigned int order)
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);
}
}
@@ -856,6 +857,10 @@ static int free_tail_pages_check(struct page *head_page, struct page *page)
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;
@@ -866,6 +871,7 @@ static int free_tail_pages_check(struct page *head_page, struct page *page)
}
ret = 0;
out:
+ page->mapping = NULL;
clear_compound_head(page);
return ret;
}