netdev - Re: [PATCH bpf-next v8 05/11] bpf: implement BPF_PROG_QUERY for BPF_LSM

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Date:   Sat, 4 Jun 2022 01:05:42 -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 v8 05/11] bpf: implement BPF_PROG_QUERY for
 BPF_LSM_CGROUP

On Fri, Jun 03, 2022 at 11:59:38PM -0700, Martin KaFai Lau wrote:
> On Wed, Jun 01, 2022 at 12:02:12PM -0700, Stanislav Fomichev wrote:
> > diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> > index a27a6a7bd852..cb3338ef01e0 100644
> > --- a/kernel/bpf/cgroup.c
> > +++ b/kernel/bpf/cgroup.c
> > @@ -1035,6 +1035,7 @@ 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 atype;
> > @@ -1042,50 +1043,92 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
> >  	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;
> > +	enum cgroup_bpf_attach_type from_atype, to_atype;
> >  
> > -	progs = &cgrp->bpf.progs[atype];
> > -	flags = cgrp->bpf.flags[atype];
> > +	if (type == BPF_LSM_CGROUP) {
> > +		from_atype = CGROUP_LSM_START;
> > +		to_atype = CGROUP_LSM_END;
> Enforce prog_attach_flags for BPF_LSM_CGROUP:
> 
> 		if (total_cnt && !prog_attach_flags)
Correction.  Mixed up with the total_cnt below.

Should be "attr->query.prog_cnt && prog_ids && !prog_attach_flags".

> 			return -EINVAL;
> 			


[ ... ]

> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index a237be4f8bb3..27492d44133f 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -3520,7 +3520,7 @@ static int bpf_prog_detach(const union bpf_attr *attr)
> >  	}
> >  }
> >  
> > -#define BPF_PROG_QUERY_LAST_FIELD query.prog_cnt
> > +#define BPF_PROG_QUERY_LAST_FIELD query.prog_attach_flags
> >  
> >  static int bpf_prog_query(const union bpf_attr *attr,
> >  			  union bpf_attr __user *uattr)
> > @@ -3556,6 +3556,7 @@ static int bpf_prog_query(const union bpf_attr *attr,
> >  	case BPF_CGROUP_SYSCTL:
> >  	case BPF_CGROUP_GETSOCKOPT:
> >  	case BPF_CGROUP_SETSOCKOPT:
> > +	case BPF_LSM_CGROUP:
> >  		return cgroup_bpf_prog_query(attr, uattr);
> >  	case BPF_LIRC_MODE2:
> >  		return lirc_prog_query(attr, uattr);
> > @@ -4066,6 +4067,9 @@ static int bpf_prog_get_info_by_fd(struct file *file,
> >  
> >  	if (prog->aux->btf)
> >  		info.btf_id = btf_obj_id(prog->aux->btf);
> > +	info.attach_btf_id = prog->aux->attach_btf_id;
> > +	if (prog->aux->attach_btf)
> > +		info.attach_btf_obj_id = btf_obj_id(prog->aux->attach_btf);
> Need this also:
> 
> 	else if (prog->aux->dst_prog)
> 		info.attach_btf_obj_id = btf_obj_id(prog->aux->dst_prog->aux->attach_btf);
Should be btf_obj_id(prog->aux->dst_prog->aux->btf) instead.

> 
> >  
> >  	ulen = info.nr_func_info;
> >  	info.nr_func_info = prog->aux->func_info_cnt;
> > -- 
> > 2.36.1.255.ge46751e96f-goog
> >