From: Bui Quang Minh <minhquangbui99@xxxxxxxxx> Subject: 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@xxxxxxxxx Fixes: 550a7d60bd5e35 ("mm, hugepages: add mremap() support for hugepage backed vma") Signed-off-by: Bui Quang Minh <minhquangbui99@xxxxxxxxx> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Reviewed-by: Mina Almasry <almasrymina@xxxxxxxxxx> Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/hugetlb_cgroup.h | 12 ++++++++++++ mm/hugetlb.c | 4 +++- 2 files changed, 15 insertions(+), 1 deletion(-) --- a/include/linux/hugetlb_cgroup.h~hugetlb-fix-hugetlb-cgroup-refcounting-during-mremap +++ a/include/linux/hugetlb_cgroup.h @@ -128,6 +128,13 @@ static inline void resv_map_dup_hugetlb_ css_get(resv_map->css); } +static inline void resv_map_put_hugetlb_cgroup_uncharge_info( + struct resv_map *resv_map) +{ + if (resv_map->css) + css_put(resv_map->css); +} + extern int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages, struct hugetlb_cgroup **ptr); extern int hugetlb_cgroup_charge_cgroup_rsvd(int idx, unsigned long nr_pages, @@ -210,6 +217,11 @@ static inline void resv_map_dup_hugetlb_ struct resv_map *resv_map) { } + +static inline void resv_map_put_hugetlb_cgroup_uncharge_info( + struct resv_map *resv_map) +{ +} static inline int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages, struct hugetlb_cgroup **ptr) --- a/mm/hugetlb.c~hugetlb-fix-hugetlb-cgroup-refcounting-during-mremap +++ a/mm/hugetlb.c @@ -1037,8 +1037,10 @@ void clear_vma_resv_huge_pages(struct vm */ struct resv_map *reservations = vma_resv_map(vma); - if (reservations && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) + if (reservations && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) { + resv_map_put_hugetlb_cgroup_uncharge_info(reservations); kref_put(&reservations->refs, resv_map_release); + } reset_vma_resv_huge_pages(vma); } _
