2020-09-23 16:04:04

by Lorenz Bauer

Subject: [PATCH bpf-next] bpf: explicitly size compatible_reg_types

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 <[email protected]>
Suggested-by: Alexei Starovoitov <[email protected]>
---
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

2020-09-23 16:07:21

by Andrii Nakryiko

Subject: Re: [PATCH bpf-next] bpf: explicitly size compatible_reg_types

On Wed, Sep 23, 2020 at 9:03 AM Lorenz Bauer <[email protected]> wrote:
>
> 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 <[email protected]>
> Suggested-by: Alexei Starovoitov <[email protected]>
> ---

I like this more as well.

Acked-by: Andrii Nakryiko <[email protected]>

> 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
>

2020-09-23 18:52:51

by Alexei Starovoitov

Subject: Re: [PATCH bpf-next] bpf: explicitly size compatible_reg_types

On Wed, Sep 23, 2020 at 9:05 AM Andrii Nakryiko
<[email protected]> wrote:
>
> On Wed, Sep 23, 2020 at 9:03 AM Lorenz Bauer <[email protected]> wrote:
> >
> > 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 <[email protected]>
> > Suggested-by: Alexei Starovoitov <[email protected]>
> > ---
>
> I like this more as well.
>
> Acked-by: Andrii Nakryiko <[email protected]>

Applied. Thanks