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()
Fixes: 550a7d6 (mm, hugepages: add mremap() support for hugepage backed vma)
Signed-off-by: Bui Quang Minh <minhquangbui99@xxxxxxxxx>
---
include/linux/hugetlb_cgroup.h | 12 ++++++++++++
mm/hugetlb.c | 4 +++-
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
index c137396129db..ba025ae27882 100644
--- a/include/linux/hugetlb_cgroup.h
+++ b/include/linux/hugetlb_cgroup.h
@@ -128,6 +128,13 @@ static inline void resv_map_dup_hugetlb_cgroup_uncharge_info(
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,
@@ -211,6 +218,11 @@ static inline void resv_map_dup_hugetlb_cgroup_uncharge_info(
{
}
+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)
{
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e09159c957e3..3a2479003ddf 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1037,8 +1037,10 @@ void clear_vma_resv_huge_pages(struct vm_area_struct *vma)
*/
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);
}
--
2.25.1
