ksm: fix unlocked iteration over vmas in cmp_and_merge_page()
In this place mm is unlocked, so vmas or list may change. Down read
mmap_sem to protect them from modifications.
Link: http://lkml.kernel.org/r/150512788393.10691.8868381099691121308.stgit@localhost.localdomain
Fixes: e86c59b1b1
("mm/ksm: improve deduplication of zero pages with colouring")
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: zhong jiang <zhongjiang@huawei.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
fa87b91c94
commit
4b22927f0c
5
mm/ksm.c
5
mm/ksm.c
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@ -1990,6 +1990,7 @@ static void stable_tree_append(struct rmap_item *rmap_item,
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*/
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*/
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static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
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static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
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{
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{
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struct mm_struct *mm = rmap_item->mm;
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struct rmap_item *tree_rmap_item;
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struct rmap_item *tree_rmap_item;
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struct page *tree_page = NULL;
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struct page *tree_page = NULL;
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struct stable_node *stable_node;
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struct stable_node *stable_node;
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@ -2062,9 +2063,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
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if (ksm_use_zero_pages && (checksum == zero_checksum)) {
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if (ksm_use_zero_pages && (checksum == zero_checksum)) {
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struct vm_area_struct *vma;
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struct vm_area_struct *vma;
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vma = find_mergeable_vma(rmap_item->mm, rmap_item->address);
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down_read(&mm->mmap_sem);
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vma = find_mergeable_vma(mm, rmap_item->address);
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err = try_to_merge_one_page(vma, page,
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err = try_to_merge_one_page(vma, page,
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ZERO_PAGE(rmap_item->address));
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ZERO_PAGE(rmap_item->address));
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up_read(&mm->mmap_sem);
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/*
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/*
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* In case of failure, the page was not really empty, so we
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* In case of failure, the page was not really empty, so we
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* need to continue. Otherwise we're done.
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* need to continue. Otherwise we're done.
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