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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Fri, Jun 3, 2022 at 11:59 PM Martin KaFai Lau <kafai@xxxxxx> 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)
>                         return -EINVAL;

All the comments make sense, will apply. The only thing that I'll
probably keep as is is the copy_to_user(flags) part. We can't move it
above because it hasn't been properly initialized there.

What I think I'll do is:

if (atype != to_atype) /* exported via prog_attach_flags */
  flags = 0;
copy_to_user(.., flags,..);

That seems to better describe why we're not doing it?


> > +     } else {
> > +             from_atype = to_cgroup_bpf_attach_type(type);
> > +             if (from_atype < 0)
> > +                     return -EINVAL;
> > +             to_atype = 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];
> > +             flags = cgrp->bpf.flags[atype];
> >
> > -     if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE)
> > -             cnt = bpf_prog_array_length(effective);
> > -     else
> > -             cnt = prog_list_length(progs);
> > +             effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
> > +                                                   lockdep_is_held(&cgroup_mutex));
> nit. This can be done under the BPF_F_QUERY_EFFECTIVE case below.
>
> >
> > -     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 (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE)
> > +                     total_cnt += bpf_prog_array_length(effective);
> > +             else
> > +                     total_cnt += prog_list_length(progs);
> > +     }
> > +
> > +     if (type != BPF_LSM_CGROUP)
> > +             if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
> > +                     return -EFAULT;
> nit. Move this copy_to_user(&uattr->query.attach_flags,...) to the
> 'if (type == BPF_LSM_CGROUP) { from_atype = .... } else { ... }' above.
> That will save a BPF_LSM_CGROUP test.
>
> I think the '== BPF_LSM_CGROUP' case needs to copy a 0 to user also.
>
> > +     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; atype++) {
> > +             if (total_cnt <= 0)
> nit. total_cnt cannot be -ve ?
> !total_cnt instead ?
> and may be do it in the for-loop test.
>
> > +                     break;
> >
> > -             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;
> > +             progs = &cgrp->bpf.progs[atype];
> > +             flags = cgrp->bpf.flags[atype];
> > +
> > +             effective = rcu_dereference_protected(cgrp->bpf.effective[atype],
> > +                                                   lockdep_is_held(&cgroup_mutex));
> nit. This can be done under the BPF_F_QUERY_EFFECTIVE case below.
>
> > +
> > +             if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE)
> > +                     cnt = bpf_prog_array_length(effective);
> > +             else
> > +                     cnt = prog_list_length(progs);
> > +
> > +             if (cnt >= total_cnt)
> > +                     cnt = total_cnt;
> nit. This seems to be the only reason that
> the "if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE)"
> need to be broken up into two halves.  One above and one below.
> It does not save much code.  How about repeating this one line
> 'cnt = min_t(int, cnt, total_cnt);' instead ?
>
> > +
> > +             if (attr->query.query_flags & BPF_F_QUERY_EFFECTIVE) {
> > +                     ret = bpf_prog_array_copy_to_user(effective, prog_ids, cnt);
> > +             } else {
> > +                     struct bpf_prog_list *pl;
> > +                     u32 id;
> > +
> > +                     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_ids += cnt;
> > +             total_cnt -= cnt;
> > +             if (prog_attach_flags)
> > +                     prog_attach_flags += cnt;
> nit. Merge this into the above "if (prog_attach_flags)" case.
>
> >       }
> >       return ret;
> >  }
> > 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);
>
> >
> >       ulen = info.nr_func_info;
> >       info.nr_func_info = prog->aux->func_info_cnt;
> > --
> > 2.36.1.255.ge46751e96f-goog
> >



[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux