[PATCH bpf-next] bpf: explicitly size compatible_reg_types

[Lorenz Bauer]

Arrays with designated initializers have an implicit length of the highest
initialized value plus one. I used this to ensure that newly added entries
in enum bpf_reg_type get a NULL entry in compatible_reg_types.

This is difficult to understand since it requires knowledge of the
peculiarities of designated initializers. Use __BPF_ARG_TYPE_MAX to size
the array instead.

Signed-off-by: Lorenz Bauer <l...@cloudflare.com>
Suggested-by: Alexei Starovoitov <a...@kernel.org>
---
 kernel/bpf/verifier.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 15ab889b0a3f..d7c993ded26a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4002,7 +4002,7 @@ static const struct bpf_reg_types const_map_ptr_types = { 
.types = { CONST_PTR_T
 static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } 
};
 static const struct bpf_reg_types spin_lock_types = { .types = { 
PTR_TO_MAP_VALUE } };
 
-static const struct bpf_reg_types *compatible_reg_types[] = {
+static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
        [ARG_PTR_TO_MAP_KEY]            = &map_key_value_types,
        [ARG_PTR_TO_MAP_VALUE]          = &map_key_value_types,
        [ARG_PTR_TO_UNINIT_MAP_VALUE]   = &map_key_value_types,
@@ -4025,7 +4025,6 @@ static const struct bpf_reg_types *compatible_reg_types[] 
= {
        [ARG_PTR_TO_ALLOC_MEM_OR_NULL]  = &alloc_mem_types,
        [ARG_PTR_TO_INT]                = &int_ptr_types,
        [ARG_PTR_TO_LONG]               = &int_ptr_types,
-       [__BPF_ARG_TYPE_MAX]            = NULL,
 };
 
 static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
-- 
2.25.1