netdev - Re: [PATCH bpf-next v9 05/10] bpf: implement BPF_PROG_QUERY for BPF_LSM

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Message-ID: <20220617005829.66pboow5uubbrdcu@kafai-mbp>
Date:   Thu, 16 Jun 2022 17:58:29 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org
Subject: Re: [PATCH bpf-next v9 05/10] bpf: implement BPF_PROG_QUERY for
 BPF_LSM_CGROUP

On Fri, Jun 10, 2022 at 09:57:58AM -0700, Stanislav Fomichev wrote:
> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> index ba402d50e130..c869317479ec 100644
> --- a/kernel/bpf/cgroup.c
> +++ b/kernel/bpf/cgroup.c
> @@ -1029,57 +1029,92 @@ static int cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
>  static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
>  			      union bpf_attr __user *uattr)
>  {
> +	__u32 __user *prog_attach_flags = u64_to_user_ptr(attr->query.prog_attach_flags);
>  	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
>  	enum bpf_attach_type type = attr->query.attach_type;
> +	enum cgroup_bpf_attach_type from_atype, to_atype;
>  	enum cgroup_bpf_attach_type atype;
>  	struct bpf_prog_array *effective;
>  	struct hlist_head *progs;
>  	struct bpf_prog *prog;
>  	int cnt, ret = 0, i;
> +	int total_cnt = 0;
>  	u32 flags;
>  
> -	atype = to_cgroup_bpf_attach_type(type);
> -	if (atype < 0)
> -		return -EINVAL;
> +	if (type == BPF_LSM_CGROUP) {
> +		if (attr->query.prog_cnt && prog_ids && !prog_attach_flags)
> +			return -EINVAL;
>  
> -	progs = &cgrp->bpf.progs[atype];
> -	flags = cgrp->bpf.flags[atype];
> +		from_atype = CGROUP_LSM_START;
> +		to_atype = CGROUP_LSM_END;
> +		flags = 0;
> +	} else {
> +		from_atype = to_cgroup_bpf_attach_type(type);
> +		if (from_atype < 0)
> +			return -EINVAL;
> +		to_atype = from_atype;
> +		flags = cgrp->bpf.flags[from_atype];
> +	}
>  
> -	effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
> -					      lockdep_is_held(&cgroup_mutex));
> +	for (atype = from_atype; atype <= to_atype; atype++) {
> +		progs = &cgrp->bpf.progs[atype];
nit. Move the 'progs = ...' into the 'else {}' case below.

>  
> -	if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE)
> -		cnt = bpf_prog_array_length(effective);
> -	else
> -		cnt = prog_list_length(progs);
> +		if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
> +			effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
> +							      lockdep_is_held(&cgroup_mutex));
> +			total_cnt += bpf_prog_array_length(effective);
> +		} else {
> +			total_cnt += prog_list_length(progs);
> +		}
> +	}
>  
>  	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
>  		return -EFAULT;
> -	if (copy_to_user(&uattr->query.prog_cnt, &cnt, sizeof(cnt)))
> +	if (copy_to_user(&uattr->query.prog_cnt, &total_cnt, sizeof(total_cnt)))
>  		return -EFAULT;
> -	if (attr->query.prog_cnt == 0 || !prog_ids || !cnt)
> +	if (attr->query.prog_cnt == 0 || !prog_ids || !total_cnt)
>  		/* return early if user requested only program count + flags */
>  		return 0;
> -	if (attr->query.prog_cnt < cnt) {
> -		cnt = attr->query.prog_cnt;
> +
> +	if (attr->query.prog_cnt < total_cnt) {
> +		total_cnt = attr->query.prog_cnt;
>  		ret = -ENOSPC;
>  	}
>  
> -	if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
> -		return bpf_prog_array_copy_to_user(effective, prog_ids, cnt);
> -	} else {
> -		struct bpf_prog_list *pl;
> -		u32 id;
> +	for (atype = from_atype; atype <= to_atype && total_cnt; atype++) {
> +		progs = &cgrp->bpf.progs[atype];
same here.

> +		flags = cgrp->bpf.flags[atype];
and the 'flags = ...' can be moved to 'if (prog_attach_flags) {}'

Others lgtm.

Reviewed-by: Martin KaFai Lau <kafai@...com>

>  
> -		i = 0;
> -		hlist_for_each_entry(pl, progs, node) {
> -			prog = prog_list_prog(pl);
> -			id = prog->aux->id;
> -			if (copy_to_user(prog_ids + i, &id, sizeof(id)))
> -				return -EFAULT;
> -			if (++i == cnt)
> -				break;
> +		if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
> +			effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
> +							      lockdep_is_held(&cgroup_mutex));
> +			cnt = min_t(int, bpf_prog_array_length(effective), total_cnt);
> +			ret = bpf_prog_array_copy_to_user(effective, prog_ids, cnt);
> +		} else {
> +			struct bpf_prog_list *pl;
> +			u32 id;
> +
> +			cnt = min_t(int, prog_list_length(progs), total_cnt);
> +			i = 0;
> +			hlist_for_each_entry(pl, progs, node) {
> +				prog = prog_list_prog(pl);
> +				id = prog->aux->id;
> +				if (copy_to_user(prog_ids + i, &id, sizeof(id)))
> +					return -EFAULT;
> +				if (++i == cnt)
> +					break;
> +			}
>  		}
> +
> +		if (prog_attach_flags) {
> +			for (i = 0; i < cnt; i++)
> +				if (copy_to_user(prog_attach_flags + i, &flags, sizeof(flags)))
> +					return -EFAULT;
> +			prog_attach_flags += cnt;
> +		}
> +
> +		prog_ids += cnt;
> +		total_cnt -= cnt;
>  	}
>  	return ret;
>  }