stable inclusion
from stable-5.10.67
commit e1fa3b2b60abb9f43b937741e27c6531ef4cbef9
bugzilla: 182619 https://gitee.com/openeuler/kernel/issues/I4EWO7

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e1fa3b2b60abb9f43b937741e27c6531ef4cbef9

--------------------------------

commit 09a26e83 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: e9fe92ae ("hugetlb_cgroup: add reservation accounting for private mappings")
Signed-off-by: NMike Kravetz <mike.kravetz@oracle.com>
Reported-by: NGuillaume Morin <guillaume@morinfr.org>
Suggested-by: NGuillaume Morin <guillaume@morinfr.org>
Tested-by: NGuillaume Morin <guillaume@morinfr.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>