[PATCH bpf] bpf: fix NULL deref in btf_type_is_resolve_source_only

[Stanislav Fomichev]

Commit 1dc92851849c ("bpf: kernel side support for BTF Var and DataSec")
added invocations of btf_type_is_resolve_source_only before
btf_type_nosize_or_null which checks for the NULL pointer.
Swap the order of btf_type_nosize_or_null and
btf_type_is_resolve_source_only to make sure the do the NULL pointer
check first.

Fixes: 1dc92851849c ("bpf: kernel side support for BTF Var and DataSec")
Reported-by: syzbot <syzkal...@googlegroups.com>
Signed-off-by: Stanislav Fomichev <s...@google.com>
---
 kernel/bpf/btf.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index cad09858a5f2..546ebee39e2a 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -1928,8 +1928,8 @@ static int btf_array_resolve(struct btf_verifier_env *env,
        /* Check array->index_type */
        index_type_id = array->index_type;
        index_type = btf_type_by_id(btf, index_type_id);
-       if (btf_type_is_resolve_source_only(index_type) ||
-           btf_type_nosize_or_null(index_type)) {
+       if (btf_type_nosize_or_null(index_type) ||
+           btf_type_is_resolve_source_only(index_type)) {
                btf_verifier_log_type(env, v->t, "Invalid index");
                return -EINVAL;
        }
@@ -1948,8 +1948,8 @@ static int btf_array_resolve(struct btf_verifier_env *env,
        /* Check array->type */
        elem_type_id = array->type;
        elem_type = btf_type_by_id(btf, elem_type_id);
-       if (btf_type_is_resolve_source_only(elem_type) ||
-           btf_type_nosize_or_null(elem_type)) {
+       if (btf_type_nosize_or_null(elem_type) ||
+           btf_type_is_resolve_source_only(elem_type)) {
                btf_verifier_log_type(env, v->t,
                                      "Invalid elem");
                return -EINVAL;
@@ -2170,8 +2170,8 @@ static int btf_struct_resolve(struct btf_verifier_env 
*env,
                const struct btf_type *member_type = btf_type_by_id(env->btf,
                                                                member_type_id);
 
-               if (btf_type_is_resolve_source_only(member_type) ||
-                   btf_type_nosize_or_null(member_type)) {
+               if (btf_type_nosize_or_null(member_type) ||
+                   btf_type_is_resolve_source_only(member_type)) {
                        btf_verifier_log_member(env, v->t, member,
                                                "Invalid member");
                        return -EINVAL;
-- 
2.22.0.410.gd8fdbe21b5-goog