Re: [PATCH v4 bpf-next 08/14] bpf: introduce the bpf_get_local_storage() helper function
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2018-07-31 22:50:28
Also in:
lkml
On 07/27/2018 11:52 PM, Roman Gushchin wrote: [...]
quoted hunk ↗ jump to hunk
@@ -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]);