linux-kernel - Re: [bpf-next, v2] bpf: verifier: Fix potential memleak and UAF in bpf verifier

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Date:   Wed, 14 Jul 2021 18:34:15 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Song Liu <song@...nel.org>
Cc:     He Fengqing <hefengqing@...wei.com>,
        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>,
        "David S . Miller" <davem@...emloft.net>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [bpf-next, v2] bpf: verifier: Fix potential memleak and UAF in
 bpf verifier

On Wed, Jul 14, 2021 at 5:54 PM Song Liu <song@...nel.org> wrote:
> > -       return 0;
> > +       return;
> No need to say return here.
>
> >  }
> >
> >  static void adjust_subprog_starts(struct bpf_verifier_env *env, u32 off, u32 len)
> > @@ -11492,6 +11490,14 @@ static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 of
> >                                             const struct bpf_insn *patch, u32 len)
> >  {
> >         struct bpf_prog *new_prog;
> > +       struct bpf_insn_aux_data *new_data = NULL;
> > +
> > +       if (len > 1) {
> > +               new_data = vzalloc(array_size(env->prog->len + len - 1,
> > +                                             sizeof(struct bpf_insn_aux_data)));
> > +               if (!new_data)
> > +                       return NULL;

I removed the redundant 'return' that Song pointed out and the
redundant 'if' above.
And applied to bpf-next.
Though it's a fix, I think it's ok to go via bpf-next, since even
syzbot didn't find it.