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: <6E50D47F-EC06-417C-8512-9CAA3734821E@meta.com>
Date: Fri, 20 Jun 2025 20:48:22 +0000
From: Song Liu <songliubraving@...a.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
CC: Song Liu <song@...nel.org>, 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 Jun 20, 2025, at 11:18 AM, Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
> 
> 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.

Makes sense. I will add it to common_btf_ids in v3. 

Thanks,
Song