netdev - Re: [PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for BPF_CGROUP_INET_SOCK

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Message-ID: <aaf5eeb5-2336-4a20-9b8f-0cdd3c274ff0@linux.dev>
Date: Wed, 27 Aug 2025 15:23:35 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 John Fastabend <john.fastabend@...il.com>,
 Stanislav Fomichev <sdf@...ichev.me>, Johannes Weiner <hannes@...xchg.org>,
 Michal Hocko <mhocko@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>,
 Shakeel Butt <shakeel.butt@...ux.dev>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Neal Cardwell <ncardwell@...gle.com>, Willem de Bruijn <willemb@...gle.com>,
 Mina Almasry <almasrymina@...gle.com>, Kuniyuki Iwashima
 <kuni1840@...il.com>, bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3 bpf-next/net 2/5] bpf: Support bpf_setsockopt() for
 BPF_CGROUP_INET_SOCK_CREATE.

On 8/26/25 11:38 AM, Kuniyuki Iwashima wrote:
> We will store a flag in sk->sk_memcg by bpf_setsockopt() during
> socket() or before sk->sk_memcg is set in accept().
> 
> BPF_CGROUP_INET_SOCK_CREATE is invoked by __cgroup_bpf_run_filter_sk()
> that passes a pointer to struct sock to the bpf prog as void *ctx.
> 
> But there are no bpf_func_proto for bpf_setsockopt() that receives
> the ctx as a pointer to struct sock.
> 
> Let's add a new bpf_setsockopt() variant for BPF_CGROUP_INET_SOCK_CREATE.
> 
> Note that inet_create() is not under lock_sock().
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
> ---
> v3: Remove bpf_func_proto for accept()
> v2: Make 2 new bpf_func_proto static
> ---
>   net/core/filter.c | 24 ++++++++++++++++++++++++
>   1 file changed, 24 insertions(+)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 63f3baee2daf..443d12b7d3b2 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5743,6 +5743,23 @@ static const struct bpf_func_proto bpf_sock_ops_setsockopt_proto = {
>   	.arg5_type	= ARG_CONST_SIZE,
>   };
>   
> +BPF_CALL_5(bpf_unlocked_sock_setsockopt, struct sock *, sk, int, level,
> +	   int, optname, char *, optval, int, optlen)
> +{
> +	return _bpf_setsockopt(sk, level, optname, optval, optlen);

The sock_owned_by_me() will warn.

 From CI:
WARNING: CPU: 0 PID: 102 at include/net/sock.h:1756 bpf_unlocked_sock_setsockopt+0xc7/0x110

> +}
> +
> +static const struct bpf_func_proto bpf_unlocked_sock_setsockopt_proto = {
> +	.func		= bpf_unlocked_sock_setsockopt,
> +	.gpl_only	= false,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_PTR_TO_CTX,
> +	.arg2_type	= ARG_ANYTHING,
> +	.arg3_type	= ARG_ANYTHING,
> +	.arg4_type	= ARG_PTR_TO_MEM | MEM_RDONLY,
> +	.arg5_type	= ARG_CONST_SIZE,
> +};
> +
>   static int bpf_sock_ops_get_syn(struct bpf_sock_ops_kern *bpf_sock,
>   				int optname, const u8 **start)
>   {
> @@ -8051,6 +8068,13 @@ sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>   		return &bpf_sk_storage_get_cg_sock_proto;
>   	case BPF_FUNC_ktime_get_coarse_ns:
>   		return &bpf_ktime_get_coarse_ns_proto;
> +	case BPF_FUNC_setsockopt:
> +		switch (prog->expected_attach_type) {
> +		case BPF_CGROUP_INET_SOCK_CREATE:
> +			return &bpf_unlocked_sock_setsockopt_proto;
> +		default:
> +			return NULL;
> +		}
>   	default:
>   		return bpf_base_func_proto(func_id, prog);
>   	}