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    Subject[PATCH 5.15 046/244] bpf: Acquire map uref in .init_seq_private for sock local storage map iterator
    Date
    From: Hou Tao <houtao1@huawei.com>

    commit 3c5f6e698b5c538bbb23cd453b22e1e4922cffd8 upstream.

    bpf_iter_attach_map() acquires a map uref, and the uref may be released
    before or in the middle of iterating map elements. For example, the uref
    could be released in bpf_iter_detach_map() as part of
    bpf_link_release(), or could be released in bpf_map_put_with_uref() as
    part of bpf_map_release().

    So acquiring an extra map uref in bpf_iter_init_sk_storage_map() and
    releasing it in bpf_iter_fini_sk_storage_map().

    Fixes: 5ce6e77c7edf ("bpf: Implement bpf iterator for sock local storage map")
    Signed-off-by: Hou Tao <houtao1@huawei.com>
    Acked-by: Yonghong Song <yhs@fb.com>
    Acked-by: Martin KaFai Lau <kafai@fb.com>
    Link: https://lore.kernel.org/r/20220810080538.1845898-4-houtao@huaweicloud.com
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/core/bpf_sk_storage.c | 10 +++++++++-
    1 file changed, 9 insertions(+), 1 deletion(-)

    --- a/net/core/bpf_sk_storage.c
    +++ b/net/core/bpf_sk_storage.c
    @@ -865,10 +865,18 @@ static int bpf_iter_init_sk_storage_map(
    {
    struct bpf_iter_seq_sk_storage_map_info *seq_info = priv_data;

    + bpf_map_inc_with_uref(aux->map);
    seq_info->map = aux->map;
    return 0;
    }

    +static void bpf_iter_fini_sk_storage_map(void *priv_data)
    +{
    + struct bpf_iter_seq_sk_storage_map_info *seq_info = priv_data;
    +
    + bpf_map_put_with_uref(seq_info->map);
    +}
    +
    static int bpf_iter_attach_map(struct bpf_prog *prog,
    union bpf_iter_link_info *linfo,
    struct bpf_iter_aux_info *aux)
    @@ -914,7 +922,7 @@ static const struct seq_operations bpf_s
    static const struct bpf_iter_seq_info iter_seq_info = {
    .seq_ops = &bpf_sk_storage_map_seq_ops,
    .init_seq_private = bpf_iter_init_sk_storage_map,
    - .fini_seq_private = NULL,
    + .fini_seq_private = bpf_iter_fini_sk_storage_map,
    .seq_priv_size = sizeof(struct bpf_iter_seq_sk_storage_map_info),
    };


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