Re: [PATCH bpf 4/9] bpf: Acquire map uref in .init_seq_private for sock{map,hash} 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), sock_map_iter_attach_target() has already
> acquired a map uref, but the uref may be released by bpf_link_release()
> during th reading of map iterator.
> 
> Fixing it by acquiring an extra map uref in .init_seq_private and
> releasing it in .fini_seq_private.
> 
> Fixes: 0365351524d7 ("net: Allow iterating sockmap and sockhash")
> 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/sock_map.c | 20 +++++++++++++++++++-
>   1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index 028813dfecb0..9a9fb9487d63 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -783,13 +783,22 @@ static int sock_map_init_seq_private(void *priv_data,
>   {
>   	struct sock_map_seq_info *info = priv_data;
>   
> +	bpf_map_inc_with_uref(aux->map);
>   	info->map = aux->map;
>   	return 0;
>   }
>   
> +static void sock_map_fini_seq_private(void *priv_data)
> +{
> +	struct sock_map_seq_info *info = priv_data;
> +
> +	bpf_map_put_with_uref(info->map);
> +}
> +
>   static const struct bpf_iter_seq_info sock_map_iter_seq_info = {
>   	.seq_ops		= &sock_map_seq_ops,
>   	.init_seq_private	= sock_map_init_seq_private,
> +	.fini_seq_private	= sock_map_fini_seq_private,
>   	.seq_priv_size		= sizeof(struct sock_map_seq_info),
>   };
>   
> @@ -1369,18 +1378,27 @@ static const struct seq_operations sock_hash_seq_ops = {
>   };
>   
>   static int sock_hash_init_seq_private(void *priv_data,
> -				     struct bpf_iter_aux_info *aux)
> +				      struct bpf_iter_aux_info *aux)
>   {
>   	struct sock_hash_seq_info *info = priv_data;
>   
> +	bpf_map_inc_with_uref(aux->map);
>   	info->map = aux->map;
>   	info->htab = container_of(aux->map, struct bpf_shtab, map);
>   	return 0;
>   }
>   
> +static void sock_hash_fini_seq_private(void *priv_data)
> +{
> +	struct sock_hash_seq_info *info = priv_data;
> +
> +	bpf_map_put_with_uref(info->map);
> +}
> +
>   static const struct bpf_iter_seq_info sock_hash_iter_seq_info = {
>   	.seq_ops		= &sock_hash_seq_ops,
>   	.init_seq_private	= sock_hash_init_seq_private,
> +	.fini_seq_private	= sock_hash_fini_seq_private,
>   	.seq_priv_size		= sizeof(struct sock_hash_seq_info),
>   };
>