Re: [PATCH bpf 3/9] bpf: Acquire map uref in .init_seq_private for sock local storage map iterator

[Yonghong Song <yhs@fb.com>]

On 8/6/22 12:40 AM, Hou Tao wrote:
> From: Hou Tao <houtao1@huawei.com>
> 
> During bpf(BPF_LINK_CREATE) for BPF_TRACE_ITER, bpf_iter_attach_map()
> has already acquired a map uref, but the uref may be released
> by bpf_link_release() during th reading of map iterator.
> 
> 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>

See my previous reply for some wording issue.

Acked-by: Yonghong Song <yhs@fb.com>

> ---
>   net/core/bpf_sk_storage.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
> index a25ec93729b9..83b89ba824d7 100644
> --- a/net/core/bpf_sk_storage.c
> +++ b/net/core/bpf_sk_storage.c
> @@ -875,10 +875,18 @@ static int bpf_iter_init_sk_storage_map(void *priv_data,
>   {
>   	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)
> @@ -924,7 +932,7 @@ static const struct seq_operations bpf_sk_storage_map_seq_ops = {
>   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),
>   };
>