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Commit afe041c2 authored by Bui Quang Minh's avatar Bui Quang Minh Committed by Linus Torvalds
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hugetlb: fix hugetlb cgroup refcounting during mremap

When hugetlb_vm_op_open() is called during copy_vma(), we may take the
reference to resv_map->css.  Later, when clearing the reservation
pointer of old_vma after transferring it to new_vma, we forget to drop
the reference to resv_map->css.  This leads to a reference leak of css.

Fixes this by adding a check to drop reservation css reference in
clear_vma_resv_huge_pages()

Link: https://lkml.kernel.org/r/20211113154412.91134-1-minhquangbui99@gmail.com


Fixes: 550a7d60 ("mm, hugepages: add mremap() support for hugepage backed vma")
Signed-off-by: default avatarBui Quang Minh <minhquangbui99@gmail.com>
Reviewed-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: default avatarMina Almasry <almasrymina@google.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 34dbc3aa
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