linux-kernel - Re: [PATCH v2 bpf-next 5/5] bpf: Make bpf_cgroup_read_xattr available to cgroup and struct

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Message-ID: <CAADnVQLCyk4O6w4WRxTKcQsEdZ3y6_CNc4mBF2ieT9m51E+2Lw@mail.gmail.com>
Date: Fri, 20 Jun 2025 11:18:23 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Song Liu <song@...nel.org>
Cc: bpf <bpf@...r.kernel.org>, Linux-Fsdevel <linux-fsdevel@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	LSM List <linux-security-module@...r.kernel.org>, Kernel Team <kernel-team@...a.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Eduard <eddyz87@...il.com>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, KP Singh <kpsingh@...nel.org>, 
	Matt Bobrowski <mattbobrowski@...gle.com>, Amir Goldstein <amir73il@...il.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Tejun Heo <tj@...nel.org>, 
	Daan De Meyer <daan.j.demeyer@...il.com>
Subject: Re: [PATCH v2 bpf-next 5/5] bpf: Make bpf_cgroup_read_xattr available
 to cgroup and struct_ops progs

On Thu, Jun 19, 2025 at 3:02 PM Song Liu <song@...nel.org> wrote:
>
> cgroup BPF programs and struct_ops BPF programs (such as sched_ext), need
> bpf_cgroup_read_xattr. Make bpf_cgroup_read_xattr available to these prog
> types.

...

> +       ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_LSM, &bpf_lsm_fs_kfunc_set);
> +       ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_fs_kfunc_set);
> +       ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SKB, &bpf_fs_kfunc_set);
> +       ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCK, &bpf_fs_kfunc_set);
> +       ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_DEVICE, &bpf_fs_kfunc_set);
> +       ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCK_ADDR, &bpf_fs_kfunc_set);
> +       ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SYSCTL, &bpf_fs_kfunc_set);
> +       return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCKOPT, &bpf_fs_kfunc_set);

No need to artificially restrict it like this.
bpf_cgroup_read_xattr() is generic enough and the verifier will enforce
the safety due to KF_RCU.
Just add it to common_btf_ids.