[PATCH bpf 2/4] bpf: don't set id on after map lookup with ptr_to_map_val return

[Daniel Borkmann]

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 <dan...@iogearbox.net>
Cc: Roman Gushchin <g...@fb.com>
Acked-by: Alexei Starovoitov <a...@kernel.org>
---
 kernel/bpf/verifier.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 774fa40..1971ca32 100644
--- a/kernel/bpf/verifier.c
+++ b/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)
-- 
2.9.5