bpf: Disallow bpf_obj_new_impl call when bpf_mem_alloc_init fails

In the unlikely event that bpf_global_ma is not correctly initialized,
instead of checking the boolean everytime bpf_obj_new_impl is called,
simply check it while loading the program and return an error if
bpf_global_ma_set is false.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221120212610.2361700-1-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/helpers.c

@@ -1760,8 +1760,6 @@ void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
 	u64 size = local_type_id__k;
 	void *p;
 
-	if (unlikely(!bpf_global_ma_set))
-		return NULL;
 	p = bpf_mem_alloc(&bpf_global_ma, size);
 	if (!p)
 		return NULL;

kernel/bpf/verifier.c

@@ -8878,6 +8878,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 				struct btf *ret_btf;
 				u32 ret_btf_id;
 
+				if (unlikely(!bpf_global_ma_set))
+					return -ENOMEM;
+
 				if (((u64)(u32)meta.arg_constant.value) != meta.arg_constant.value) {
 					verbose(env, "local type ID argument must be in range [0, U32_MAX]\n");
 					return -EINVAL;