Re: [PATCH bpf-next v5 3/5] bpf: Add helper to detect indirect jump targets

[Alexei Starovoitov]

On Wed, Mar 4, 2026 at 4:46 AM Xu Kuohai <xukuohai@xxxxxxxxxxxxxxx> wrote:
>
> On 3/4/2026 1:19 AM, Alexei Starovoitov wrote:
>
> [...]
>
> >> -       for (i = 0; i < insn_cnt; i++, insn++) {
> >> +       for (i = 0, j = 0; i < insn_cnt; i++, j++, insn++) {
> >> +               env->insn_aux_data[subprog_start + j].final_idx = i;
> >>                  if (bpf_pseudo_func(insn)) {
> >>                          /* ld_imm64 with an address of bpf subprog is not
> >>                           * a user controlled constant. Don't randomize it,
> >> @@ -1512,6 +1542,8 @@ struct bpf_prog *bpf_jit_blind_constants(struct bpf_verifier_env *env, struct bp
> >>                           */
> >>                          insn++;
> >>                          i++;
> >> +                       j++;
> >> +                       env->insn_aux_data[subprog_start + j].final_idx = i;
> >
> > You're adding final_idx because bpf_jit_blind_constants()
> > doesn't call adjust_insn_aux_data() ?
> >
>
> Yes, I added final_idx because insn_aux is not updated here.
>
> > imo that's an ugly workaround. Just call adjust_insn_aux_data().
> >
>
> If we adjust the env->insn_aux_data here, should we also adjust the global
> env->prog->insnsi array? I think env->insn_aux_data should remain consistent
> with the global env->prog->insnsi array. Since constant blinding only rewrites
> the subprog's private instruction array, updating the env->insn_aux_data
> causes a mismatch with the global state.

yes, and subprog starts, and pokes that bpf_patch_insn_data() do.

blinding was implemented long before that, so it was never updated.