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Date:   Wed, 20 Apr 2022 15:30:43 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCH bpf-next] bpf: use bpf_prog_run_array_cg_flags everywhere

On Wed, Apr 20, 2022 at 3:04 PM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Tue, Apr 19, 2022 at 3:23 PM Stanislav Fomichev <sdf@...gle.com> wrote:
> >
> > Rename bpf_prog_run_array_cg_flags to bpf_prog_run_array_cg and
> > use it everywhere. check_return_code already enforces sane
> > return ranges for all cgroup types. (only egress and bind hooks have
> > uncanonical return ranges, the rest is using [0, 1])
> >
> > No functional changes.
> >
> > Suggested-by: Alexei Starovoitov <ast@...nel.org>
> > Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> > ---
> >  include/linux/bpf-cgroup.h |  8 ++---
> >  kernel/bpf/cgroup.c        | 70 ++++++++++++--------------------------
> >  2 files changed, 24 insertions(+), 54 deletions(-)
> >
> > diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
> > index 88a51b242adc..669d96d074ad 100644
> > --- a/include/linux/bpf-cgroup.h
> > +++ b/include/linux/bpf-cgroup.h
> > @@ -225,24 +225,20 @@ static inline bool cgroup_bpf_sock_enabled(struct sock *sk,
> >
> >  #define BPF_CGROUP_RUN_SA_PROG(sk, uaddr, atype)                                      \
> >  ({                                                                            \
> > -       u32 __unused_flags;                                                    \
> >         int __ret = 0;                                                         \
> >         if (cgroup_bpf_enabled(atype))                                         \
> >                 __ret = __cgroup_bpf_run_filter_sock_addr(sk, uaddr, atype,     \
> > -                                                         NULL,                \
> > -                                                         &__unused_flags);    \
> > +                                                         NULL, NULL);         \
> >         __ret;                                                                 \
> >  })
> >
> >  #define BPF_CGROUP_RUN_SA_PROG_LOCK(sk, uaddr, atype, t_ctx)                  \
> >  ({                                                                            \
> > -       u32 __unused_flags;                                                    \
> >         int __ret = 0;                                                         \
> >         if (cgroup_bpf_enabled(atype))  {                                      \
> >                 lock_sock(sk);                                                 \
> >                 __ret = __cgroup_bpf_run_filter_sock_addr(sk, uaddr, atype,     \
> > -                                                         t_ctx,               \
> > -                                                         &__unused_flags);    \
> > +                                                         t_ctx, NULL);        \
> >                 release_sock(sk);                                              \
> >         }                                                                      \
> >         __ret;                                                                 \
> > diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> > index 0cb6211fcb58..f61eca32c747 100644
> > --- a/kernel/bpf/cgroup.c
> > +++ b/kernel/bpf/cgroup.c
> > @@ -25,50 +25,18 @@ EXPORT_SYMBOL(cgroup_bpf_enabled_key);
> >  /* __always_inline is necessary to prevent indirect call through run_prog
> >   * function pointer.
> >   */
> > -static __always_inline int
> > -bpf_prog_run_array_cg_flags(const struct cgroup_bpf *cgrp,
> > -                           enum cgroup_bpf_attach_type atype,
> > -                           const void *ctx, bpf_prog_run_fn run_prog,
> > -                           int retval, u32 *ret_flags)
> > -{
> > -       const struct bpf_prog_array_item *item;
> > -       const struct bpf_prog *prog;
> > -       const struct bpf_prog_array *array;
> > -       struct bpf_run_ctx *old_run_ctx;
> > -       struct bpf_cg_run_ctx run_ctx;
> > -       u32 func_ret;
> > -
> > -       run_ctx.retval = retval;
> > -       migrate_disable();
> > -       rcu_read_lock();
> > -       array = rcu_dereference(cgrp->effective[atype]);
> > -       item = &array->items[0];
> > -       old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> > -       while ((prog = READ_ONCE(item->prog))) {
> > -               run_ctx.prog_item = item;
> > -               func_ret = run_prog(prog, ctx);
> > -               if (!(func_ret & 1) && !IS_ERR_VALUE((long)run_ctx.retval))
> > -                       run_ctx.retval = -EPERM;
> > -               *(ret_flags) |= (func_ret >> 1);
> > -               item++;
> > -       }
> > -       bpf_reset_run_ctx(old_run_ctx);
> > -       rcu_read_unlock();
> > -       migrate_enable();
> > -       return run_ctx.retval;
> > -}
> > -
> >  static __always_inline int
> >  bpf_prog_run_array_cg(const struct cgroup_bpf *cgrp,
> >                       enum cgroup_bpf_attach_type atype,
> >                       const void *ctx, bpf_prog_run_fn run_prog,
> > -                     int retval)
> > +                     int retval, u32 *ret_flags)
> >  {
> >         const struct bpf_prog_array_item *item;
> >         const struct bpf_prog *prog;
> >         const struct bpf_prog_array *array;
> >         struct bpf_run_ctx *old_run_ctx;
> >         struct bpf_cg_run_ctx run_ctx;
> > +       u32 func_ret;
> >
> >         run_ctx.retval = retval;
> >         migrate_disable();
> > @@ -78,8 +46,11 @@ bpf_prog_run_array_cg(const struct cgroup_bpf *cgrp,
> >         old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> >         while ((prog = READ_ONCE(item->prog))) {
> >                 run_ctx.prog_item = item;
> > -               if (!run_prog(prog, ctx) && !IS_ERR_VALUE((long)run_ctx.retval))
> > +               func_ret = run_prog(prog, ctx);
> > +               if (!(func_ret & 1) && !IS_ERR_VALUE((long)run_ctx.retval))
>
> to be completely true to previous behavior, shouldn't there be
>
> if (ret_flags)
>     func_ret &= 1;
> if (!func_ret && !IS_ERR_VALUE(...))
>
> here?
>
> This might have been discussed previously and I missed it. If that's
> so, please ignore.

We are converting the cases where run_prog(prog, ctx) returns 0 or 1,
so it seems like we don't have to reproduce the existing behavior
1-to-1?
So I'm not sure it matters, or am I missing something?

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