On 07/27/2018 11:52 PM, Roman Gushchin wrote:
[...]
> @@ -2533,6 +2541,16 @@ static int check_helper_call(struct bpf_verifier_env
> *env, int func_id, int insn
> }
>
> regs = cur_regs(env);
> +
> + /* check that flags argument in get_local_storage(map, flags) is 0,
> + * this is required because get_local_storage() can't return an error.
> + */
> + if (func_id == BPF_FUNC_get_local_storage &&
> + !tnum_equals_const(regs[BPF_REG_2].var_off, 0)) {
> + verbose(env, "get_local_storage() doesn't support non-zero
> flags\n");
> + return -EINVAL;
> + }
Hmm, this check is actually not correct. You will still be able to pass non-zero
values in there. arg2_type from the helper is ARG_ANYTHING, so the register type
could for example be one of the pointer types and it will still pass the
verifier.
The correct way to check would be to use register_is_null().
> +
> /* reset caller saved regs */
> for (i = 0; i < CALLER_SAVED_REGS; i++) {
> mark_reg_not_init(env, regs, caller_saved[i]);
