Re: [PATCH bpf-next v3 03/17] bpf/verifier: prevent non GPL programs to be loaded against HID

[Song Liu <song@kernel.org>]

On Fri, Mar 18, 2022 at 9:16 AM Benjamin Tissoires
<benjamin.tissoires@redhat.com> wrote:
>
> This is just to hammer the obvious because I suspect you can not already
> load a bpf HID program which is not GPL because all of the useful
> functions are GPL only.
>
> Anyway, this ensures that users are not tempted to bypass this requirement
> and will allow us to ship tested BPF programs in the kernel without having
> to aorry about the license.
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

Acked-by: Song Liu <songliubraving@fb.com>


>
> ---
>
> no changes in v3
>
> new in v2:
>  - Note: I placed this statement in check_attach_btf_id() to be local to
>    other similar checks (regarding LSM), however, I have no idea if this
>    is the correct place. Please shout at me if it isn't.
> ---
>  include/linux/bpf-hid.h |  8 ++++++++
>  kernel/bpf/hid.c        | 12 ++++++++++++
>  kernel/bpf/verifier.c   |  7 +++++++
>  3 files changed, 27 insertions(+)
>
> diff --git a/include/linux/bpf-hid.h b/include/linux/bpf-hid.h
> index 9c8dbd389995..7f596554fe8c 100644
> --- a/include/linux/bpf-hid.h
> +++ b/include/linux/bpf-hid.h
> @@ -2,6 +2,7 @@
>  #ifndef _BPF_HID_H
>  #define _BPF_HID_H
>
> +#include <linux/bpf_verifier.h>
>  #include <linux/mutex.h>
>  #include <uapi/linux/bpf.h>
>  #include <uapi/linux/bpf_hid.h>
> @@ -69,6 +70,8 @@ int bpf_hid_prog_query(const union bpf_attr *attr,
>                        union bpf_attr __user *uattr);
>  int bpf_hid_link_create(const union bpf_attr *attr,
>                         struct bpf_prog *prog);
> +int bpf_hid_verify_prog(struct bpf_verifier_log *vlog,
> +                       const struct bpf_prog *prog);
>  #else
>  static inline int bpf_hid_prog_query(const union bpf_attr *attr,
>                                      union bpf_attr __user *uattr)
> @@ -81,6 +84,11 @@ static inline int bpf_hid_link_create(const union bpf_attr *attr,
>  {
>         return -EOPNOTSUPP;
>  }
> +static inline int bpf_hid_verify_prog(struct bpf_verifier_log *vlog,
> +                                     const struct bpf_prog *prog)
> +{
> +       return -EOPNOTSUPP;
> +}
>  #endif
>
>  static inline bool bpf_hid_link_empty(struct bpf_hid *bpf,
> diff --git a/kernel/bpf/hid.c b/kernel/bpf/hid.c
> index c21dc05f6207..2dfeaaa8a83f 100644
> --- a/kernel/bpf/hid.c
> +++ b/kernel/bpf/hid.c
> @@ -34,6 +34,18 @@ void bpf_hid_set_hooks(struct bpf_hid_hooks *hooks)
>  }
>  EXPORT_SYMBOL_GPL(bpf_hid_set_hooks);
>
> +int bpf_hid_verify_prog(struct bpf_verifier_log *vlog,
> +                       const struct bpf_prog *prog)
> +{
> +       if (!prog->gpl_compatible) {
> +               bpf_log(vlog,
> +                       "HID programs must have a GPL compatible license\n");
> +               return -EINVAL;
> +       }
> +
> +       return 0;
> +}
> +
>  BPF_CALL_3(bpf_hid_get_data, struct hid_bpf_ctx_kern*, ctx, u64, offset, u64, size)
>  {
>         if (!size)
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index cf92f9c01556..da06d633fb8d 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -21,6 +21,7 @@
>  #include <linux/perf_event.h>
>  #include <linux/ctype.h>
>  #include <linux/error-injection.h>
> +#include <linux/bpf-hid.h>
>  #include <linux/bpf_lsm.h>
>  #include <linux/btf_ids.h>
>
> @@ -14272,6 +14273,12 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
>         if (prog->type == BPF_PROG_TYPE_STRUCT_OPS)
>                 return check_struct_ops_btf_id(env);
>
> +       if (prog->type == BPF_PROG_TYPE_HID) {
> +               ret = bpf_hid_verify_prog(&env->log, prog);
> +               if (ret < 0)
> +                       return ret;
> +       }
> +
>         if (prog->type != BPF_PROG_TYPE_TRACING &&
>             prog->type != BPF_PROG_TYPE_LSM &&
>             prog->type != BPF_PROG_TYPE_EXT)
> --
> 2.35.1
>