bpf: don't set id on after map lookup with ptr_to_map_val return

In the verifier there is no such semantics where registers with
PTR_TO_MAP_VALUE type have an id assigned to them. This is only
used in PTR_TO_MAP_VALUE_OR_NULL and later on nullified once the
test against NULL has been pattern matched and type transformed
into PTR_TO_MAP_VALUE.

Fixes: 3e6a4b3e0289 ("bpf/verifier: introduce BPF_PTR_TO_MAP_VALUE")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Roman Gushchin <guro@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/verifier.c

@@ -2852,10 +2852,6 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 		regs[BPF_REG_0].type = NOT_INIT;
 	} else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL ||
 		   fn->ret_type == RET_PTR_TO_MAP_VALUE) {
-		if (fn->ret_type == RET_PTR_TO_MAP_VALUE)
-			regs[BPF_REG_0].type = PTR_TO_MAP_VALUE;
-		else
-			regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
 		/* There is no offset yet applied, variable or fixed */
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		/* remember map_ptr, so that check_map_access()
@@ -2868,7 +2864,12 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 			return -EINVAL;
 		}
 		regs[BPF_REG_0].map_ptr = meta.map_ptr;
-		regs[BPF_REG_0].id = ++env->id_gen;
+		if (fn->ret_type == RET_PTR_TO_MAP_VALUE) {
+			regs[BPF_REG_0].type = PTR_TO_MAP_VALUE;
+		} else {
+			regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
+			regs[BPF_REG_0].id = ++env->id_gen;
+		}
 	} else if (fn->ret_type == RET_PTR_TO_SOCKET_OR_NULL) {
 		int id = acquire_reference_state(env, insn_idx);
 		if (id < 0)