On Mon, Sep 21, 2020 at 01:12:27PM +0100, Lorenz Bauer wrote:
> +struct bpf_reg_types {
> + const enum bpf_reg_type types[10];
> +};
any idea on how to make it more robust?
> +
> +static const struct bpf_reg_types *compatible_reg_types[] = {
> + [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,
> + [ARG_PTR_TO_MAP_VALUE_OR_NULL] = &map_key_value_types,
> + [ARG_CONST_SIZE] = &scalar_types,
> + [ARG_CONST_SIZE_OR_ZERO] = &scalar_types,
> + [ARG_CONST_ALLOC_SIZE_OR_ZERO] = &scalar_types,
> + [ARG_CONST_MAP_PTR] = &const_map_ptr_types,
> + [ARG_PTR_TO_CTX] = &context_types,
> + [ARG_PTR_TO_CTX_OR_NULL] = &context_types,
> + [ARG_PTR_TO_SOCK_COMMON] = &sock_types,
> + [ARG_PTR_TO_SOCKET] = &fullsock_types,
> + [ARG_PTR_TO_SOCKET_OR_NULL] = &fullsock_types,
> + [ARG_PTR_TO_BTF_ID] = &btf_ptr_types,
> + [ARG_PTR_TO_SPIN_LOCK] = &spin_lock_types,
> + [ARG_PTR_TO_MEM] = &mem_types,
> + [ARG_PTR_TO_MEM_OR_NULL] = &mem_types,
> + [ARG_PTR_TO_UNINIT_MEM] = &mem_types,
> + [ARG_PTR_TO_ALLOC_MEM] = &alloc_mem_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,
I don't understand what this extra value is for.
I tried:
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index fc5c901c7542..87b0d5dcc1ff 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -292,7 +292,6 @@ enum bpf_arg_type {
ARG_PTR_TO_ALLOC_MEM, /* pointer to dynamically allocated memory */
ARG_PTR_TO_ALLOC_MEM_OR_NULL, /* pointer to dynamically allocated memory or NULL */
ARG_CONST_ALLOC_SIZE_OR_ZERO, /* number of allocated bytes requested */
- __BPF_ARG_TYPE_MAX,
};
/* type of values returned from helper functions */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 15ab889b0a3f..83faa67858b6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -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,
};
and everything is fine as I think it should be.
> + compatible = compatible_reg_types[arg_type];
> + if (!compatible) {
> + verbose(env, "verifier internal error: unsupported arg type %d\n", arg_type);
> return -EFAULT;
> }
This check will trigger the same way when somebody adds new ARG_* and doesn't add to the table.
>
> + err = check_reg_type(env, regno, compatible);
> + if (err)
> + return err;
> +
> if (type == PTR_TO_BTF_ID) {
> const u32 *btf_id = fn->arg_btf_id[arg];
>
> @@ -4174,10 +4213,6 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
> }
>
> return err;
> -err_type:
> - verbose(env, "R%d type=%s expected=%s\n", regno,
> - reg_type_str[type], reg_type_str[expected_type]);
> - return -EACCES;
I'm not a fan of table driven checks. I think one explicit switch statement
would have been easier to read, but I guess we can convert back to it later if
table becomes too limiting. The improvement in the verifier output is important
and justifies this approach.
Applied to bpf-next. Thanks!
