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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
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')
-rw-r--r--mm/huge_memory.c2
-rw-r--r--mm/memory.c2
-rw-r--r--mm/page_alloc.c6
-rw-r--r--mm/util.c10
4 files changed, 14 insertions, 6 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f952f055fdcf..370d44a5e25b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1805,7 +1805,7 @@ static void __split_huge_page_refcount(struct page *page,
*/
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 --git a/mm/memory.c b/mm/memory.c
index d4e4d37c1989..f9360dde6967 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3096,7 +3096,7 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
* 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 --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;
}
diff --git a/mm/util.c b/mm/util.c
index 2d28f7930043..8acb936a52c8 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -386,7 +386,9 @@ struct anon_vma *page_anon_vma(struct page *page)
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)))
@@ -399,10 +401,10 @@ struct address_space *page_mapping(struct page *page)
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,