netdev - Re: [PATCH bpf-next] bpf, x86_64: fail gracefully on bpf_jit_binary_pack

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Date:   Tue, 8 Feb 2022 09:28:18 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Song Liu <song@...nel.org>
Cc:     bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next] bpf, x86_64: fail gracefully on
 bpf_jit_binary_pack_finalize failures

On Mon, Feb 7, 2022 at 10:26 PM Song Liu <song@...nel.org> wrote:
>
> Instead of BUG_ON(), fail gracefully and return orig_prog.
>
> Fixes: 1022a5498f6f ("bpf, x86_64: Use bpf_jit_binary_pack_alloc")
> Signed-off-by: Song Liu <song@...nel.org>
> ---
>  arch/x86/net/bpf_jit_comp.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index 643f38b91e30..08e8fd8f954a 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -2380,7 +2380,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>                          *
>                          * Both cases are serious bugs that we should not continue.

I tweaked that comment a bit, since it's no longer accurate and
pushed to bpf-next.
Thanks!

>                          */
> -                       BUG_ON(bpf_jit_binary_pack_finalize(prog, header, rw_header));
> +                       if (WARN_ON(bpf_jit_binary_pack_finalize(prog, header, rw_header))) {
> +                               prog = orig_prog;
> +                               goto out_addrs;
> +                       }
> +
>                         bpf_tail_call_direct_fixup(prog);
>                 } else {
>                         jit_data->addrs = addrs;
> --
> 2.30.2
>