linux-hardening - Re: [PATCH 0/2] bpf: Build with -Wcast-function-type

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Date:   Mon, 27 Sep 2021 22:24:32 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 0/2] bpf: Build with -Wcast-function-type

On Mon, Sep 27, 2021 at 11:27 AM Kees Cook <keescook@...omium.org> wrote:
>
> Hi,
>
> In order to keep ahead of cases in the kernel where Control Flow Integrity
> (CFI) may trip over function call casts, enabling -Wcast-function-type
> is helpful. To that end, replace BPF_CAST_CALL() as it triggers warnings
> with this option and is now one of the last places in the kernel in need
> of fixing.
>
> Thanks,
>
> -Kees
>
> Kees Cook (2):
>   bpf: Replace "want address" users of BPF_CAST_CALL with BPF_CALL_IMM
>   bpf: Replace callers of BPF_CAST_CALL with proper function typedef
>

Both patches look good to me. For the series:

Acked-by: Andrii Nakryiko <andrii@...nel.org>

>  include/linux/bpf.h    |  4 +++-
>  include/linux/filter.h |  7 +++----
>  kernel/bpf/arraymap.c  |  7 +++----
>  kernel/bpf/hashtab.c   | 13 ++++++-------
>  kernel/bpf/helpers.c   |  5 ++---
>  kernel/bpf/verifier.c  | 26 +++++++++-----------------
>  6 files changed, 26 insertions(+), 36 deletions(-)
>
> --
> 2.30.2
>