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hugetlb: fix hugetlb cgroup refcounting during vma split
commit09a26e8327
upstream. Guillaume Morin reported hitting the following WARNING followed by GPF or NULL pointer deference either in cgroups_destroy or in the kill_css path.: percpu ref (css_release) <= 0 (-1) after switching to atomic WARNING: CPU: 23 PID: 130 at lib/percpu-refcount.c:196 percpu_ref_switch_to_atomic_rcu+0x127/0x130 CPU: 23 PID: 130 Comm: ksoftirqd/23 Kdump: loaded Tainted: G O 5.10.60 #1 RIP: 0010:percpu_ref_switch_to_atomic_rcu+0x127/0x130 Call Trace: rcu_core+0x30f/0x530 rcu_core_si+0xe/0x10 __do_softirq+0x103/0x2a2 run_ksoftirqd+0x2b/0x40 smpboot_thread_fn+0x11a/0x170 kthread+0x10a/0x140 ret_from_fork+0x22/0x30 Upon further examination, it was discovered that the css structure was associated with hugetlb reservations. For private hugetlb mappings the vma points to a reserve map that contains a pointer to the css. At mmap time, reservations are set up and a reference to the css is taken. This reference is dropped in the vma close operation; hugetlb_vm_op_close. However, if a vma is split no additional reference to the css is taken yet hugetlb_vm_op_close will be called twice for the split vma resulting in an underflow. Fix by taking another reference in hugetlb_vm_op_open. Note that the reference is only taken for the owner of the reserve map. In the more common fork case, the pointer to the reserve map is cleared for non-owning vmas. Link: https://lkml.kernel.org/r/20210830215015.155224-1-mike.kravetz@oracle.com Fixes:e9fe92ae0c
("hugetlb_cgroup: add reservation accounting for private mappings") Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Reported-by: Guillaume Morin <guillaume@morinfr.org> Suggested-by: Guillaume Morin <guillaume@morinfr.org> Tested-by: Guillaume Morin <guillaume@morinfr.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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2 changed files with 15 additions and 1 deletions
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@ -121,6 +121,13 @@ static inline void hugetlb_cgroup_put_rsvd_cgroup(struct hugetlb_cgroup *h_cg)
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css_put(&h_cg->css);
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}
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static inline void resv_map_dup_hugetlb_cgroup_uncharge_info(
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struct resv_map *resv_map)
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{
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if (resv_map->css)
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css_get(resv_map->css);
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}
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extern int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
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struct hugetlb_cgroup **ptr);
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extern int hugetlb_cgroup_charge_cgroup_rsvd(int idx, unsigned long nr_pages,
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@ -199,6 +206,11 @@ static inline void hugetlb_cgroup_put_rsvd_cgroup(struct hugetlb_cgroup *h_cg)
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{
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}
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static inline void resv_map_dup_hugetlb_cgroup_uncharge_info(
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struct resv_map *resv_map)
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{
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}
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static inline int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
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struct hugetlb_cgroup **ptr)
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{
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@ -4033,8 +4033,10 @@ static void hugetlb_vm_op_open(struct vm_area_struct *vma)
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* after this open call completes. It is therefore safe to take a
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* new reference here without additional locking.
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*/
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if (resv && is_vma_resv_set(vma, HPAGE_RESV_OWNER))
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if (resv && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
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resv_map_dup_hugetlb_cgroup_uncharge_info(resv);
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kref_get(&resv->refs);
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}
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}
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static void hugetlb_vm_op_close(struct vm_area_struct *vma)
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