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authorKirill Tkhai <ktkhai@virtuozzo.com>2017-10-04 02:14:27 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-10-04 03:54:23 +0300
commit4b22927f0cbd58303aac689e378d20bf56267a39 (patch)
treec62d33d5689dda2c2f0bcb259f13e0c99dd89ada /mm/ksm.c
parentfa87b91c94a8fd2c8502b6761be2d08a8e9bcf55 (diff)
downloadlinux-4b22927f0cbd58303aac689e378d20bf56267a39.tar.xz
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: e86c59b1b12d ("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>
Diffstat (limited to 'mm/ksm.c')
-rw-r--r--mm/ksm.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index 15dd7415f7b3..6cb60f46cce5 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1990,6 +1990,7 @@ static void stable_tree_append(struct rmap_item *rmap_item,
*/
static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
{
+ struct mm_struct *mm = rmap_item->mm;
struct rmap_item *tree_rmap_item;
struct page *tree_page = NULL;
struct stable_node *stable_node;
@@ -2062,9 +2063,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
if (ksm_use_zero_pages && (checksum == zero_checksum)) {
struct vm_area_struct *vma;
- vma = find_mergeable_vma(rmap_item->mm, rmap_item->address);
+ down_read(&mm->mmap_sem);
+ vma = find_mergeable_vma(mm, rmap_item->address);
err = try_to_merge_one_page(vma, page,
ZERO_PAGE(rmap_item->address));
+ up_read(&mm->mmap_sem);
/*
* In case of failure, the page was not really empty, so we
* need to continue. Otherwise we're done.