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Date:   Wed, 20 Apr 2022 15:04:01 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Stanislav Fomichev <sdf@...gle.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 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.


>                         run_ctx.retval = -EPERM;
> +               if (ret_flags)
> +                       *(ret_flags) |= (func_ret >> 1);
>                 item++;
>         }
>         bpf_reset_run_ctx(old_run_ctx);

[..]

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